This is one of the simpler manipulations you could make to a floating
point number.
Backports commit 0bfc9f195209593e91a98cf2233753f56a2e5c02 from qemu
These are considerably simpler as the lower order integers can just
use the higher order conversion function. As the decomposed fractional
part is a full 64 bit rounding and inexact handling comes from the
pack functions.
Backports commit c02e1fb80b553d47420f7492de4bc590c2461a86 from qemu
We share the common int64/uint64_pack_decomposed function across all
the helpers and simply limit the final result depending on the final
size.
Backports commit ab52f973a504f8de0c5df64631ba4caea70a7d9e from qemu
We can now add float16_round_to_int and use the common round_decomposed and
canonicalize functions to have a single implementation for
float16/32/64 round_to_int functions.
Backports commit dbe4d53a590f5689772b683984588b3cf6df163e from qemu
We can now add float16_muladd and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 muladd functions.
Backports commit d446830a3aac33e7221e361dad3ab1e1892646cb from qemu
We can now add float16_div and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 versions.
Backports commit cf07323d494f4bc225e405688c2e455c3423cc40 from qemu
We can now add float16_mul and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 versions.
Backports commit 74d707e2cc1e406068acad8e5559cd2584b1073a from qemu
We can now add float16_add/sub and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 add and sub functions.
Backports commit 6fff216769cf7eaa3961c85dee7a72838696d365 from qemu
We can now add float16_add/sub and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 add and sub functions.
Backports commit 6fff216769cf7eaa3961c85dee7a72838696d365 from qemu
This defines the same set of common constants for float 16 as defined
for 32 and 64 bit floats. These are often used by target helper
functions. I've also removed constants that are not used by anybody.
Backports commit efd4829edfa036c5506a16d05c91268faa1f6332 from qemu
This will be required when expanding the MINMAX() macro for 16
bit/half-precision operations.
Backports commit 28136775cd99c628f7d7c642b04eb87f062efef8 from qemu
As cpu.h is another typically widely included file which doesn't need
full access to the softfloat API we can remove the includes from here
as well. Where they do need types it's typically for float_status and
the rounding modes so we move that to softfloat-types.h as well.
As a result of not having softfloat in every cpu.h call we now need to
add it to various helpers that do need the full softfloat.h
definitions.
Backports commit 24f91e81b65fcdd0552d1f0fcb0ea7cfe3829c19 from qemu
The main culprit here is bswap.h which pulled in softfloat.h so it
could use the types in its CPU_Float* and ldfl/stfql functions. As
bswap.h is very widely included this added a compile dependency every
time we touch softfloat.h. Move the typedefs for each float type into
their own file so we don't re-build the world every time we tweak the
main softfloat.h header.
Backports commit cfd88fc6f2722def193f5ef271381d8f6e2a2526 from qemu
It's not actively built and when enabled things fail to compile. I'm
not sure the type-checking is really helping here. Seeing as we "own"
our softfloat now lets remove the cruft.
Backports commit a9579fff616563ca34977af68c9646c8f7be1120 from qemu
This will be required when expanding the MINMAX() macro for 16
bit/half-precision operations.
Backports commit 210cbd4910ae9e41e0a1785b96890ea2c291b381 from qemu
This cleanup makes the number of objects depending on qapi/qmp/qlist.h
drop from 4551 (out of 4743) to 16 in my "build everything" tree.
While there, separate #include from file comment with a blank line.
Backports commit 47e6b297e76007c04a1e9c492006fe093d932cd9 from qemu
This generic function (along with its implementations for different
types) determines whether two QObjects are equal.
Backports commit b38dd678a21582e03ecd2dec76ccf8290455628a from qemu
The macro expansions of qdict_put_TYPE() and qlist_append_TYPE() need
qbool.h, qnull.h, qnum.h and qstring.h to compile. We include qnull.h
and qnum.h in the headers, but not qbool.h and qstring.h. Works,
because we include those wherever the macros get used.
Open-coding these helpers is of dubious value. Turn them into
functions and drop the includes from the headers.
This cleanup makes the number of objects depending on qapi/qmp/qnum.h
from 4551 (out of 4743) to 46 in my "build everything" tree. For
qapi/qmp/qnull.h, the number drops from 4552 to 21.
Backports commit 15280c360e54a65e2c7be1a47bfbe41dce1ef986 from qemu
compare_litqobj_to_qobj() lacks a qlit_ prefix. Moreover, "compare"
suggests -1, 0, +1 for less than, equal and greater than. The
function actually returns non-zero for equal, zero for unequal.
Rename to qlit_equal_qobject().
Its return type will be cleaned up in the next patch.
Backports commit 60cc2eb7afd40b9cbaa35a5e0b54f365ac6e49f1 from qemu
The QLIT_QFOO() macros expand into compound literals. Sadly, gcc
doesn't recognizes these as constant expressions (clang does), which
makes the macros useless for initializing objects with static storage
duration.
There is a gcc bug about it:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71713
Change the macros to expand into initializers.
Backports commit d5cd8fbf130312bea91823c41de87d55818d599b from qemu
Make visit_type_null() take an @obj argument like its buddies. This
helps keep the next commit simple.
Backports commit d2f95f4d482374485234790a6fc3cca29ebb7355 from qemu
qapi/qmp/types.h is a convenience header to include a number of
qapi/qmp/ headers. Since we rarely need all of the headers
qapi/qmp/types.h includes, we bypass it most of the time. Most of the
places that use it don't need all the headers, either.
Include the necessary headers directly, and drop qapi/qmp/types.h.
Backports commit 6b67395762a4c8b6ca94364e0a0f616a6470c46a from qemu
This renders many inclusions of qapi/qmp/q*.h superfluous. They'll be
dropped in the next few commits.
Backports commit 9f5c734d591e26186a71f9e36d752f4798df3672 from qemu
The MC68040 MMU provides the size of the access that
triggers the page fault.
This size is set in the Special Status Word which
is written in the stack frame of the access fault
exception.
So we need the size in m68k_cpu_unassigned_access() and
m68k_cpu_handle_mmu_fault().
To be able to do that, this patch modifies the prototype of
handle_mmu_fault handler, tlb_fill() and probe_write().
do_unassigned_access() already includes a size parameter.
This patch also updates handle_mmu_fault handlers and
tlb_fill() of all targets (only parameter, no code change).
Backports commit 98670d47cd8d63a529ff230fd39ddaa186156f8c from qemu
With no fixed array allocation, we can't overflow a buffer.
This will be important as optimizations related to host vectors
may expand the number of ops used.
Use QTAILQ to link the ops together.
Backports commit 15fa08f8451babc88d733bd411d4c94976f9d0f8 from qemu
Normally we create an address space for that CPU and pass that address
space into the function. Let's just do it inside to unify address space
creations. It'll simplify my next patch to rename those address spaces.
Backports commit 80ceb07a83375e3a0091591f96bd47bce2f640ce from qemu
This was never used since its introduction in commit
196ea13104f8 ("memory: Add global-locking property to memory
regions").
Backports commit e2fbe20851ceec5ccd7b539a89db0420393fb85d from qemu
In our various supported host OSes, the time_t type may be either 32
or 64 bit, and could in theory also be either signed or unsigned.
Notably, in OpenBSD time_t is a 64 bit type even if 'long' is 32
bits, so using LONG_MAX for TIME_MAX is incorrect.
Use an approach suggested by Paolo Bonzini which calculates
the maximum value of the type rather than hardcoding it;
to do this we use the TYPE_MAXIMUM macro from Gnulib.
Backports commit e7b47c22e2df14d55e3e4426688c929bf8e3f7fb from qemu
The GET and MAKE functions weren't really specific enough.
We now have a full complement of functions that convert exactly
between temporaries, arguments, tcgv pointers, and indices.
The target/sparc change is also a bug fix, which would have affected
a host that defines TCG_TARGET_HAS_extr[lh]_i64_i32, i.e. MIPS64.
Backports commit dc41aa7d34989b552efe712ffe184236216f960b from qemu
Transform TCGv_* to an "argument" or a temporary.
For now, an argument is simply the temporary index.
Backports commit ae8b75dc6ec808378487064922f25f1e7ea7a9be from qemu
DEFINE_TYPES() will help to simplify following routine patterns:
static void foo_register_types(void)
{
type_register_static(&foo1_type_info);
type_register_static(&foo2_type_info);
...
}
type_init(foo_register_types)
or
static void foo_register_types(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(type_infos); i++) {
type_register_static(&type_infos[i]);
}
}
type_init(foo_register_types)
with a single line
DEFINE_TYPES(type_infos)
where types have static definition which could be consolidated in
a single array of TypeInfo structures.
It saves us ~6-10LOC per use case and would help to replace
imperative foo_register_types() there with declarative style of
type registration.
Backports commit 38b5d79b2e8cf6085324066d84e8bb3b3bbe8548 from qemu
it will help to remove code duplication of registration
static types in places that have open coded loop to
perform batch type registering.
Backports commit aa04c9d20704fa5b9ab239d5111adbcce5f49808 from qemu
In preparation for adding tc.size to be able to keep track of
TB's using the binary search tree implementation from glib.
Backports commit e7e168f41364c6e83d0f75fc1b3ce7f9c41ccf76 from qemu
And fix the following warning when DEBUG_TB_INVALIDATE is enabled
in translate-all.c:
CC mipsn32-linux-user/accel/tcg/translate-all.o
/data/src/qemu/accel/tcg/translate-all.c: In function ‘tb_alloc_page’:
/data/src/qemu/accel/tcg/translate-all.c:1201:16: error: format ‘%lx’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘tb_page_addr_t {aka unsigned int}’ [-Werror=format=]
printf("protecting code page: 0x" TARGET_FMT_lx "\n",
^
cc1: all warnings being treated as errors
/data/src/qemu/rules.mak:66: recipe for target 'accel/tcg/translate-all.o' failed
make[1]: *** [accel/tcg/translate-all.o] Error 1
Makefile:328: recipe for target 'subdir-mipsn32-linux-user' failed
make: *** [subdir-mipsn32-linux-user] Error 2
cota@flamenco:/data/src/qemu/build ((18f3fe1...) *$)$
Backports commit 67a5b5d2f6eb6d3b980570223ba5c478487ddb6f from qemu
We have object_get_objects_root() to keep user created objects, however
no place for objects that will be used internally. Create such a
container for internal objects.
Backports commit 7c47c4ead75d0b733ee8f2f51fd1de0644cc1308 from qemu
Provide helpers to convert bitmaps to little endian format. It can be
used when we want to send one bitmap via network to some other hosts.
One thing to mention is that, these helpers only solve the problem of
endianess, but it does not solve the problem of different word size on
machines (the bitmaps managing same count of bits may contains different
size when malloced). So we need to take care of the size alignment issue
on the callers for now.
Backports commit d7788151a0807d5d2d410e3f8944d8c8a651f8d2 from qemu
We already have several files that knowingly require assert()
to work, sometimes because refactoring the code for proper
error handling has not been tackled yet; there are probably
other files that have a similar situation but with no comments
documenting the same. In fact, we have places in migration
that handle untrusted input with assertions, where disabling
the assertions risks a worse security hole than the current
behavior of losing the guest to SIGABRT when migration fails
because of the assertion. Promote our current per-file
safety-valve to instead be project-wide, and expand it to also
cover glib's g_assert().
Note that we do NOT want to encourage 'assert(side-effects);'
(that is a bad practice that prevents copy-and-paste of code to
other projects that CAN disable assertions; plus it costs
unnecessary reviewer mental cycles to remember whether a project
special-cases the crippling of asserts); and we would LIKE to
fix migration to not rely on asserts (but that takes a big code
audit). But in the meantime, we DO want to send a message
that anyone that disables assertions has to tweak code in order
to compile, making it obvious that they are taking on additional
risk that we are not going to support. At the same time, leave
comments mentioning NDEBUG in files that we know still need to
be scrubbed, so there is at least something to grep for.
It would be possible to come up with some other mechanism for
doing runtime checking by default, but which does not abort
the program on failure, while leaving side effects in place
(unlike how crippling assert() avoids even the side effects),
perhaps under the name q_verify(); but it was not deemed worth
the effort (developers should not have to learn a replacement
when the standard C macro works just fine, and it would be a lot
of churn for little gain). The patch specifically uses #error
rather than #warn so that a user is forced to tweak the header
to acknowledge the issue, even when not using a -Werror
compilation.
Backports commit 262a69f4282e44426c7a132138581d400053e0a1 from qemu
Split out maybe_out_small_movi for use with other operations
that want to add to the constant pool.
Backports commit 28eef8aaece5e83df4568d9842ab9611ec130b2c from qemu
Replace the USE_DIRECT_JUMP ifdef with a TCG_TARGET_HAS_direct_jump
boolean test. Replace the tb_set_jmp_target1 ifdef with an unconditional
function tb_target_set_jmp_target.
While we're touching all backends, add a parameter for tb->tc_ptr;
we're going to need it shortly for some backends.
Move tb_set_jmp_target and tb_add_jump from exec-all.h to cpu-exec.c.
Backports commit a85833933628384d74ec412024d55cf012640287 from qemu
Define a new MachineClass field ignore_memory_transaction_failures.
If this is flag is true then the CPU will ignore memory transaction
failures which should cause the CPU to take an exception due to an
access to an unassigned physical address; the transaction will
instead return zero (for a read) or be ignored (for a write). This
should be set only by legacy board models which rely on the old
RAZ/WI behaviour for handling devices that QEMU does not yet model.
New board models should instead use "unimplemented-device" for all
memory ranges where the guest will attempt to probe for a device that
QEMU doesn't implement and a stub device is required.
We need this for ARM boards, where we're about to implement support for
generating external aborts on memory transaction failures. Too many
of our legacy board models rely on the RAZ/WI behaviour and we
would break currently working guests when their "probe for device"
code provoked an external abort rather than a RAZ.
Backports commit ed860129acd3fcd0b1e47884e810212aaca4d21b from qemu
Used later. An enum makes expected values explicit and
bounds the value space of switches.
Backports commit 77fc6f5e28667634916f114ae04c6029cd7b9c45 from qemu
This will allow some amount of cleanup to happen before
switching the backends over to enum DisasJumpType.
Backports commit 5dc66895b0113034cd37fd5e65911d7959fc26a9 from qemu
Currently we have a rather half-baked setup for allowing CPUs to
generate exceptions on accesses to invalid memory: the CPU has a
cpu_unassigned_access() hook which the memory system calls in
unassigned_mem_write() and unassigned_mem_read() if the current_cpu
pointer is non-NULL. This was originally designed before we
implemented the MemTxResult type that allows memory operations to
report a success or failure code, which is why the hook is called
right at the bottom of the memory system. The major problem with
this is that it means that the hook can be called even when the
access was not actually done by the CPU: for instance if the CPU
writes to a DMA engine register which causes the DMA engine to begin
a transaction which has been set up by the guest to operate on
invalid memory then this will casue the CPU to take an exception
incorrectly. Another minor problem is that currently if a device
returns a transaction error then this won't turn into a CPU exception
at all.
The right way to do this is to have allow the CPU to respond
to memory system transaction failures at the point where the
CPU specific code calls into the memory system.
Define a new QOM CPU method and utility function
cpu_transaction_failed() which is called in these cases.
The functionality here overlaps with the existing
cpu_unassigned_access() because individual target CPUs will
need some work to convert them to the new system. When this
transition is complete we can remove the old cpu_unassigned_access()
code.
Backports commit 0dff0939f6fc6a7abd966d4295f06a06d7a01df9 from qemu
Move the MemTxResult type to memattrs.h. We're going to want to
use it in cpu/qom.h, which doesn't want to include all of
memory.h. In practice MemTxResult and MemTxAttrs are pretty
closely linked since both are used for the new-style
read_with_attrs and write_with_attrs callbacks, so memattrs.h
is a reasonable home for this rather than creating a whole
new header file for it.
Backports commit 3114d092b1740f9db9aa559aeb48ee387011e1da from qemu
The helper can be used for CPU object lookup using the CPU's
arch-specific ID (the one returned by CPUClass::get_arch_id()).
Backports commit 5ce46cb34eecec0bc94a4b1394763f9a1bbe20c3 from qemu
We are going to share FlatView's between AddressSpace's and per-AS
memory listeners won't suit the purpose anymore so open code
the dispatch tree rendering.
Since there is a good chance that dispatch_listener was the only
listener, this avoids address_space_update_topology_pass() if there is
no registered listeners; this should improve starting time.
This should cause no behavioural change.
Backports commit 1b04a1580917d9e41fd37ca62cbff9b4bf061e96 from qemu
When using bit-wise operations that exploit the power-of-two
nature of the second argument of ROUND_UP(), we still need to
ensure that the mask is as wide as the first argument (done
by using a ternary to force proper arithmetic promotion).
Unpatched, ROUND_UP(2ULL*1024*1024*1024*1024, 512U) produces 0,
instead of the intended 2TiB, because negation of an unsigned
32-bit quantity followed by widening to 64-bits does not
sign-extend the mask.
Broken since its introduction in commit 292c8e50 (v1.5.0).
Callers that passed the same width type to both macro parameters,
or that had other code to ensure the first parameter's maximum
runtime value did not exceed the second parameter's width, are
unaffected, but I did not audit to see which (if any) existing
clients of the macro could trigger incorrect behavior (I found
the bug while adding a new use of the macro).
While preparing the patch, checkpatch complained about poor
spacing, so I also fixed that here and in the nearby DIV_ROUND_UP.
Backports commit 33a599667a9e70588483a31286dfff8cfc27d513 from qemu
This reverts commit e2a7f28693aea7e194ec1435697ec4feb24f8a6f.
This was not supposed to go upstream yet. Reverting.
Backports commit cde0a63ad721dbb538419a00f9405587680be436 from qemu
As a precursor to later patches attempt to come up with a more
concrete wording for what each of the common exit cases would be.
Backports commit df0311e634828fdc99ca59352aef68503d631aad from qemu
Rename memory_region_init_rom() to memory_region_init_rom_nomigrate()
and memory_region_init_rom_device() to
memory_region_init_rom_device_nomigrate().
Backports commit b59821a95bd1d7cb4697fd7748725c910582e0e7 from qemu
Rename memory_region_init_ram() to memory_region_init_ram_nomigrate().
This leaves the way clear for us to provide a memory_region_init_ram()
which does handle migration.
Backports commit 1cfe48c1ce219b60a9096312f7a61806fae64ab3 from qemu
The various functions for initializing RAM MemoryRegions do not do
anything to cause the data in the MemoryRegion to be migrated.
Note in their documentation comments that this is the responsibility
of the caller.
(We will shortly add a new function that *does* do this for you.)
Backports commit a5c0234bb2754f5248e67929a34c843dbe039da5 from qemu
Add a documentation comment for memory_region_allocate_system_memory().
In particular, the reason for this function's existence and the
requirement on board code to call it exactly once are non-obvious.
Backports commit 09ad643823dcda0a86eddce1291c28d0ccb09a3b from qemu
link's check callback is supposed to verify/permit setting it,
however currently nothing restricts it from misusing it
and modifying target object from within.
Make sure that readonly semantics are checked by compiler
to prevent callback's misuse.
Backports commit 8f5d58ef2c92d7b82d9a6eeefd7c8854a183ba4a from qemu
Now that we have proper locking after MTTCG patches have landed, we
can revert the commit. This reverts commit
a9353fe897ca2687e5b3385ed39e3db3927a90e0.
Backports commit 406bc339b0505fcfc2ffcbca1f05a3756e338a65 from qemu
Add CONFIG_TCG around TLB-related functions and structure declarations.
Some of these functions are defined in ./accel/tcg/cputlb.c, which will
not be linked in if TCG is disabled, and have no stubs; therefore, their
callers will also be compiled out for --disable-tcg.
Backports commit b11ec7f2e44b285a3967d629b55d1a6970b06787 from qemu
translate-all.c will be disabled if tcg is disabled in the build,
so page_size_init() function and related variables will be moved
to exec.c file.
Backports commit a0be0c585f5dcc4d50a37f6a20d3d625c5ef3a2c from qemu
Commit 1f5c00cfdb8114c ("qom/cpu: move tlb_flush to cpu_common_reset")
moved the call to tlb_flush() from the target-specific reset handlers
into the common code qom/cpu.c file, and protected the call with
"#ifdef CONFIG_SOFTMMU" to avoid that it is called for linux-user
only targets. But since qom/cpu.c is common code, CONFIG_SOFTMMU is
*never* defined here, so the tlb_flush() was simply never executed
anymore. Fix it by introducing a wrapper for tlb_flush() in a file
that is re-compiled for each target, i.e. in translate-all.c.
Backports commit 2cd53943115be5118b5b2d4b80ee0a39c94c4f73 from qemu
Some code paths can lead to atomic accesses racing with memset()
on cpu->tb_jmp_cache, which can result in torn reads/writes
and is undefined behaviour in C11.
These torn accesses are unlikely to show up as bugs, but from code
inspection they seem possible. For example, tb_phys_invalidate does:
/* remove the TB from the hash list */
h = tb_jmp_cache_hash_func(tb->pc);
CPU_FOREACH(cpu) {
if (atomic_read(&cpu->tb_jmp_cache[h]) == tb) {
atomic_set(&cpu->tb_jmp_cache[h], NULL);
}
}
Here atomic_set might race with a concurrent memset (such as the
ones scheduled via "unsafe" async work, e.g. tlb_flush_page) and
therefore we might end up with a torn pointer (or who knows what,
because we are under undefined behaviour).
This patch converts parallel accesses to cpu->tb_jmp_cache to use
atomic primitives, thereby bringing these accesses back to defined
behaviour. The price to pay is to potentially execute more instructions
when clearing cpu->tb_jmp_cache, but given how infrequently they happen
and the small size of the cache, the performance impact I have measured
is within noise range when booting debian-arm.
Note that under "safe async" work (e.g. do_tb_flush) we could use memset
because no other vcpus are running. However I'm keeping these accesses
atomic as well to keep things simple and to avoid confusing analysis
tools such as ThreadSanitizer.
Backports commit f3ced3c59287dabc253f83f0c70aa4934470c15e from qemu
We are relying on cpu_env being defined as a global, yet most
targets (i.e. all but arm/a64) have it defined as a local variable.
Luckily all of them use the same "cpu_env" name, but really
compilation shouldn't break if the name of that local variable
changed.
Fix it by using tcg_ctx.tcg_env, which all targets set in their
translate_init function. This change also helps paving the way
for the upcoming "translation loop common to all targets" work.
Backports commit 53f6672bcf57d82b794a2cc3a3469be7d35c8653 from qemu
Add a function to round a floatx80 to the defined precision
(floatx80_rounding_precision)
Backports commit 0f72129281765ed64d26353284059f2bdcde7a23 from qemu
In order to store integer values between INT64_MAX and UINT64_MAX, add
a uint64_t internal representation.
Backports commit 61a8f418b26a2d974e38e4ae55020aca8d402d88 from qemu
Before the previous commit, parameter promote_int = true made
visit_start_alternate() with an input visitor avoid QTYPE_QINT
variants and create QTYPE_QFLOAT variants instead. This was used
where QTYPE_QINT variants were invalid.
The previous commit fused QTYPE_QINT with QTYPE_QFLOAT, rendering
promote_int useless and unused.
Backports commit 60390d2dc85ffade8981ca41e02335cb07353a6d from qemu
We would like to use a same QObject type to represent numbers, whether
they are int, uint, or floats. Getters will allow some compatibility
between the various types if the number fits other representations.
Add a few more tests while at it.
Backports commit 01b2ffcedd94ad7b42bc870e4c6936c87ad03429 from qemu
QAPI_CLONE() returns a newly allocated QAPI object. Inconvenient when
we want to clone into an existing object. QAPI_CLONE_MEMBERS() does
exactly that.
Backports commit 4626a19c86c30d96cedbac2bd44ef8103303cb37 from qemu
Rather than making lots of callers wrap a scalar in a QInt, QString,
or QBool, provide helper macros that do the wrapping automatically.
Update the Coccinelle script to make mass conversions easy, although
the conversion itself will be done as a separate patches to ease
review and backport efforts.
Backports commit a92c21591b5bb9543996538f14854ca6b528318b from qemu
Allocating an arbitrarily-sized array of tbs results in either
(a) a lot of memory wasted or (b) unnecessary flushes of the code
cache when we run out of TB structs in the array.
An obvious solution would be to just malloc a TB struct when needed,
and keep the TB array as an array of pointers (recall that tb_find_pc()
needs the TB array to run in O(log n)).
Perhaps a better solution, which is implemented in this patch, is to
allocate TB's right before the translated code they describe. This
results in some memory waste due to padding to have code and TBs in
separate cache lines--for instance, I measured 4.7% of padding in the
used portion of code_gen_buffer when booting aarch64 Linux on a
host with 64-byte cache lines. However, it can allow for optimizations
in some host architectures, since TCG backends could safely assume that
the TB and the corresponding translated code are very close to each
other in memory. See this message by rth for a detailed explanation:
https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg05172.html
Subject: Re: GSoC 2017 Proposal: TCG performance enhancements
Backports commit 6e3b2bfd6af488a896f7936e99ef160f8f37e6f2 from qemu
Instead of exporting goto_ptr directly to TCG frontends, export
tcg_gen_lookup_and_goto_ptr(), which calls goto_ptr with the pointer
returned by the lookup_tb_ptr() helper. This is the only use case
we have for goto_ptr and lookup_tb_ptr, so having this function is
very convenient. Furthermore, it trivially allows us to avoid calling
the lookup helper if goto_ptr is not implemented by the backend.
Backports commit cedbcb01529cb6cf9a2289cdbebbc63f6149fc18 from qemu
We need to coordinate with the TCG_OVERSIZED_GUEST test in cputlb.c,
and allow 64-bit atomics even though sizeof(void *) == 4.
Backports commit 374aae653499f4d405caf32b7fff0c8639113fe4 from qemu
