Intel SDM says for CPUID function 0DH, sub-function 0:
| • ECX enumerates the size (in bytes) required by the XSAVE instruction for an
| XSAVE area containing all the user state components supported by this
| processor.
| • EBX enumerates the size (in bytes) required by the XSAVE instruction for an
| XSAVE area containing all the user state components corresponding to bits
| currently set in XCR0.
Backports commit de2e68c902f7b6e438b0fa3cfedd74a06a20704f from qemu
Interrupt handling depends on various flags in env->hflags or env->hflags2,
and the exact detail were not exactly replicated between x86_cpu_has_work
and x86_cpu_exec_interrupt. Create a new function that extracts the
highest-priority non-masked interrupt, and use it in both functions.
Backports commit 92d5f1a4147c3722b5e9a8bcfb7dc261b7a8b855 from qemu
Enabling TOPOEXT is always allowed, but it can't be enabled
blindly by "-cpu host" because it may make guests crash if the
rest of the cache topology information isn't provided or isn't
consistent.
This addresses the bug reported at:
https://bugzilla.redhat.com/show_bug.cgi?id=1613277
Backports commit 7210a02c58572b2686a3a8d610c6628f87864aed from qemu
New CPU models mostly inherit features from ancestor Skylake, while addin new
features: UMIP, New Instructions ( PCONIFIG (server only), WBNOINVD,
AVX512_VBMI2, GFNI, AVX512_VNNI, VPCLMULQDQ, VAES, AVX512_BITALG),
Intel PT and 5-level paging (Server only). As well as
IA32_PRED_CMD, SSBD support for speculative execution
side channel mitigations.
Note:
For 5-level paging, Guest physical address width can be configured, with
parameter "phys-bits". Unless explicitly specified, we still use its default
value, even for Icelake-Server cpu model.
At present, hold on expose IA32_ARCH_CAPABILITIES to guest, as 1) This MSR
actually presents more than 1 'feature', maintainers are considering expanding current
features presentation of only CPUIDs to MSR bits; 2) a reasonable default value
for MSR_IA32_ARCH_CAPABILITIES needs to settled first. These 2 are actully
beyond Icelake CPU model itself but fundamental. So split these work apart
and do it later.
https://lists.gnu.org/archive/html/qemu-devel/2018-07/msg00774.htmlhttps://lists.gnu.org/archive/html/qemu-devel/2018-07/msg00796.html
Backports commit 8a11c62da9146dd89aee98947e6bd831e65a970d from qemu
WBNOINVD: Write back and do not invalidate cache, enumerated by
CPUID.(EAX=80000008H, ECX=0):EBX[bit 9].
Backports commit 59a80a19ca31a6fff9fdbb6b4cf55a5a0767c3bc from qemu
Support of IA32_PRED_CMD MSR already be enumerated by same CPUID bit as
SPEC_CTRL.
At present, mark CPUID_7_0_EDX_ARCH_CAPABILITIES unmigratable, per Paolo's
comment.
Backports commit 3fc7c73139d2d38ae80c3b0bc963b1ac1555924c from qemu
Rename DCACHE to DATA_CACHE and ICACHE to INSTRUCTION_CACHE.
This avoids conflict with Linux asm/cachectl.h macros and fixes
build failure on mips hosts.
Backports commit 5f00335aecafc9ad56592d943619d3252f8941f1 from qemu
Enable TOPOEXT feature on EPYC CPU. This is required to support
hyperthreading on VM guests. Also extend xlevel to 0x8000001E.
Disable topoext on PC_COMPAT_2_12 and keep xlevel 0x8000000a.
Backports commit e00516475c270dcb6705753da96063f95699abf2 from qemu
This is part of topoext support. To keep the compatibility, it is better
we support all the combination of nr_cores and nr_threads currently
supported. By allowing more nr_cores and nr_threads, we might end up with
more nodes than we can actually support with the real hardware. We need to
fix up the node id to make this work. We can achieve this by shifting the
socket_id bits left to address more nodes.
Backports commit 631be32155dbafa1fe886f2488127956c9120ba6 from qemu
AMD future CPUs expose a mechanism to tell the guest that the
Speculative Store Bypass Disable is not needed and that the
CPU is all good.
This is exposed via the CPUID 8000_0008.EBX[26] bit.
See 124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
A copy of this document is available at
https://bugzilla.kernel.org/show_bug.cgi?id=199889
Backports commit 254790a909a2f153d689bfa7d8e8f0386cda870d from qemu
AMD future CPUs expose _two_ ways to utilize the Intel equivalant
of the Speculative Store Bypass Disable. The first is via
the virtualized VIRT_SPEC CTRL MSR (0xC001_011f) and the second
is via the SPEC_CTRL MSR (0x48). The document titled:
124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
gives priority of SPEC CTRL MSR over the VIRT SPEC CTRL MSR.
A copy of this document is available at
https://bugzilla.kernel.org/show_bug.cgi?id=199889
Anyhow, this means that on future AMD CPUs there will be _two_ ways to
deal with SSBD.
Backports commit a764f3f7197f4d7ad8fe8424269933de912224cb from qemu
OSPKE is not a static feature flag: it changes dynamically at
runtime depending on CR4, and it was never configurable: KVM
never returned OSPKE on GET_SUPPORTED_CPUID, and on TCG enables
it automatically if CR4_PKE_MASK is set.
Remove OSPKE from the feature name array so users don't try to
configure it manually.
Backports commit 9ccb9784b57804f5c74434ad6ccb66650a015ffc from qemu
OSXAVE is not a static feature flag: it changes dynamically at
runtime depending on CR4, and it was never configurable: KVM
never returned OSXSAVE on GET_SUPPORTED_CPUID, and it is not
included in TCG_EXT_FEATURES.
Remove OSXSAVE from the feature name array so users don't try to
configure it manually.
Backports commit f1a23522b03a569f13aad49294bb4c4b1a9500c7 from qemu
Add support for cpuid leaf CPUID_8000_001E. Build the config that closely
match the underlying hardware. Please refer to the Processor Programming
Reference (PPR) for AMD Family 17h Model for more details.
Backports commit ed78467a214595a63af7800a073a03ffe37cd7db from qemu
Add information for cpuid 0x8000001D leaf. Populate cache topology information
for different cache types (Data Cache, Instruction Cache, L2 and L3) supported
by 0x8000001D leaf. Please refer to the Processor Programming Reference (PPR)
for AMD Family 17h Model for more details.
Backports commit 8f4202fb1080f86958782b1fca0bf0279f67d136 from qemu
Always initialize CPUCaches structs with cache information, even
if legacy_cache=true. Use different CPUCaches struct for
CPUID[2], CPUID[4], and the AMD CPUID leaves.
This will simplify a lot the logic inside cpu_x86_cpuid()
Backports commit a9f27ea9adc8c695197bd08f2e938ef7b4183f07 from qemu
AMD Zen expose the Intel equivalant to Speculative Store Bypass Disable
via the 0x80000008_EBX[25] CPUID feature bit.
This needs to be exposed to guest OS to allow them to protect
against CVE-2018-3639.
Backports commit 403503b162ffc33fb64cfefdf7b880acf41772cd from qemu
New microcode introduces the "Speculative Store Bypass Disable"
CPUID feature bit. This needs to be exposed to guest OS to allow
them to protect against CVE-2018-3639.
Backports commit d19d1f965904a533998739698020ff4ee8a103da from qemu
The property legacy-cache will be used to control the cache information.
If user passes "-cpu legacy-cache" then older information will
be displayed even if the hardware supports new information. Otherwise
use the statically loaded cache definitions if available.
Renamed the previous cache structures to legacy_*. If there is any change in
the cache information, then it needs to be initialized in builtin_x86_defs.
Backports commit ab8f992e3e63e91be257e4e343d386dae7be4bcb from qemu
Instead of having a collection of macros that need to be used in
complex expressions to build CPUID data, define a CPUCacheInfo
struct that can hold information about a given cache. Helper
functions will take a CPUCacheInfo struct as input to encode
CPUID leaves for a cache.
This will help us ensure consistency between cache information
CPUID leaves, and make the existing inconsistencies in CPUID info
more visible.
Backports commit 7e3482f824809e1f6ffeb5bb8103ba27a7d1a52a from qemu
The CLDEMOTE instruction hints to hardware that the cache line that
contains the linear address should be moved("demoted") from
the cache(s) closest to the processor core to a level more distant
from the processor core. This may accelerate subsequent accesses
to the line by other cores in the same coherence domain,
especially if the line was written by the core that demotes the line.
Intel Snow Ridge has added new cpu feature, CLDEMOTE.
The new cpu feature needs to be exposed to guest VM.
The bit definition:
CPUID.(EAX=7,ECX=0):ECX[bit 25] CLDEMOTE
The release document ref below link:
https://software.intel.com/sites/default/files/managed/c5/15/\
architecture-instruction-set-extensions-programming-reference.pdf
Backports commit 0da0fb062841d0dcd8ba47e4a989d2e952cdf0ff from qemu
A new cpu model called "KnightsMill" is added to model Knights Mill
processors. Compared to "Skylake-Server" cpu model, the following
features are added:
avx512_4vnniw avx512_4fmaps avx512pf avx512er avx512_vpopcntdq
and the following features are removed:
pcid invpcid clflushopt avx512dq avx512bw clwb smap rtm mpx
xsavec xgetbv1 hle
Backports commit a18495159a35e9c5973d9aa0f612a97318bf684d from qemu
Add an Error argument to cpu_exec_init() to let users collect the
error. This is in preparation to change the CPU enumeration logic
in cpu_exec_init(). With the new enumeration logic, cpu_exec_init()
can fail if cpu_index values corresponding to max_cpus have already
been handed out.
Since all current callers of cpu_exec_init() are from instance_init,
use error_abort Error argument to abort in case of an error.
Backports commit 5a790cc4b942e651fec7edc597c19b637fad5a76 from qemu
Intel processor trace should be disabled when
CPUID.(EAX=14H,ECX=0H).ECX.[bit31] is set.
Generated packets which contain IP payloads will have LIP
values when this bit is set, or IP payloads will have RIP
values.
Currently, The information of CPUID 14H is constant to make
live migration safty and this bit is always 0 in guest even
if host support LIP values.
Guest sees the bit is 0 will expect IP payloads with RIP
values, but the host CPU will generate IP payloads with
LIP values if this bit is set in HW.
To make sure the value of IP payloads correctly, Intel PT
should be disabled when bit[31] is set.
Backports relevant parts of commit c078ca968c6c7cb62781c1843d840cb0f5c72781 from qemu
define default CPU type in generic way in pc_machine_class_init()
and let common machine code to handle cpu_model parsing
Patch also introduces TARGET_DEFAULT_CPU_TYPE define for 2 purposes:
* make foo_machine_class_init() look uniform on every target
* use define in [bsd|linux]-user targets to pick default
cpu type
Backports commit 311ca98d16bbb6a2a38b38ba898baa4a4d4ab9a7 from qemu
Considering that features are converted to global properties and
global properties are automatically applied to every new instance
of created CPU (at object_new() time), there is no point in
parsing cpu_model string every time a CPU created. So move
parsing outside CPU creation loop and do it only once.
Parsing also should be done before any CPU is created so that
features would affect the first CPU a well.
Backports commit 6aff24c6a61c6fec31e555c7748ba6085b7b2c06 from qemu
Considering that features are converted to global properties and
global properties are automatically applied to every new instance
of created CPU (at object_new() time), there is no point in
parsing cpu_model string every time a CPU created. So move
parsing outside CPU creation loop and do it only once.
Parsing also should be done before any CPU is created so that
features would affect the first CPU a well.
Backports commit 6aff24c6a61c6fec31e555c7748ba6085b7b2c06 from qemu
Currently CPUClass->parse_features() is used to parse -cpu
features string and set properties on created CPU instances.
But considering that features specified by -cpu apply to every
created CPU instance, it doesn't make sense to parse the same
features string for every CPU created. It also makes every target
that cares about parsing features string explicitly call
CPUClass->parse_features() parser, which gets in a way if we
consider using generic device_add for CPU hotplug as device_add
has not a clue about CPU specific hooks.
Turns out we can use global properties mechanism to set
properties on every created CPU instance for a given type. That
way it's possible to convert CPU features into a set of global
properties for CPU type specified by -cpu cpu_model and common
Device.device_post_init() will apply them to CPU of given type
automatically regardless whether it's manually created CPU or CPU
created with help of device_add.
Backports commits 62a48a2a5798425997152dea3fc48708f9116c04 and
f313369fdb78f849ecbbd8e5d88f01ddf38786c8 from qemu
Backports commits 2994fd96d986578a342f2342501b4ad30f6d0a85,
701e3c78ce45fa630ffc6826c4b9a4218954bc7f, and
d1853231c60d16af78cf4d1608d043614bfbac0b from qemuu
Expose Intel Processor Trace feature to guest.
To make Intel PT live migration safe and get same CPUID information
with same CPU model on diffrent host. CPUID[14] is constant in this
patch. Intel PT use EPT is first supported in IceLake, the CPUID[14]
get on this machine as default value. Intel PT would be disabled
if any machine don't support this minial feature list.
Backports commit e37a5c7fa459558b5020588994707fe3fdd6616e from qemu
Add KVM_HINTS_DEDICATED performance hint, guest checks this feature bit
to determine if they run on dedicated vCPUs, allowing optimizations such
as usage of qspinlocks.
Backports commit be7773268d98176489483a315d3e2323cb0615b9 from qemu
This MSR returns the number of #SMIs that occurred on
CPU since boot.
KVM commit 52797bf9a875 ("KVM: x86: Add emulation of MSR_SMI_COUNT")
introduced support for emulating this MSR.
This commit adds support for QEMU to save/load this
MSR for migration purposes.
Backports relevant parts of commit e13713db5b609d9a83c9cfc8ba389d4215d4ba29 from qemu
When SEV is enabled, CPUID 0x8000_001F should provide additional
information regarding the feature (such as which page table bit is used
to mark the pages as encrypted etc).
The details for memory encryption CPUID is available in AMD APM
(https://support.amd.com/TechDocs/24594.pdf) Section E.4.17
Backports relevant parts of commit 6cb8f2a663a47c6e0da17fc4fb9e06abfda2bd48 from qemu
Clang 3.9 passes the CONFIG_AVX2_OPT configure test. However, the
supplied <cpuid.h> does not contain the bit_AVX2 define that we use
when detecting whether the routine can be enabled.
Introduce a qemu-specific header that uses the compiler's definition
of __cpuid et al, but supplies any missing bit_* definitions needed.
This avoids introducing any extra ifdefs to util/bufferiszero.c, and
allows quite a few to be removed from tcg/i386/tcg-target.inc.c.
Backports commit 5dd8990841a9e331d9d4838a116291698208cbb6 from qemu
This cleanup makes the number of objects depending on qapi/qmp/qdict.h
drop from 4550 (out of 4743) to 368 in my "build everything" tree.
For qapi/qmp/qobject.h, the number drops from 4552 to 390.
While there, separate #include from file comment with a blank line.
Backports commit 452fcdbc49c59884c8c284268d64baa24fea11e1 from qemu
This cleanup makes the number of objects depending on qapi/error.h
drop from 1910 (out of 4743) to 1612 in my "build everything" tree.
While there, separate #include from file comment with a blank line,
and drop a useless comment on why qemu/osdep.h is included first.
Backports commit e688df6bc4549f28534cdb001f168b8caae55b0c 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
Intel IceLake cpu has added new cpu features,AVX512_VBMI2/GFNI/
VAES/VPCLMULQDQ/AVX512_VNNI/AVX512_BITALG. Those new cpu features
need expose to guest VM.
The bit definition:
CPUID.(EAX=7,ECX=0):ECX[bit 06] AVX512_VBMI2
CPUID.(EAX=7,ECX=0):ECX[bit 08] GFNI
CPUID.(EAX=7,ECX=0):ECX[bit 09] VAES
CPUID.(EAX=7,ECX=0):ECX[bit 10] VPCLMULQDQ
CPUID.(EAX=7,ECX=0):ECX[bit 11] AVX512_VNNI
CPUID.(EAX=7,ECX=0):ECX[bit 12] AVX512_BITALG
The release document ref below link:
https://software.intel.com/sites/default/files/managed/c5/15/\
architecture-instruction-set-extensions-programming-reference.pdf
Backports commit aff9e6e46a343e1404498be4edd03db1112f0950 from qemu
EPYC-IBPB is a copy of the EPYC CPU model with
just CPUID_8000_0008_EBX_IBPB added.
Backports commit 8ebfafa796ca0cb2b035a7f06f836a675d8b48be from qemu
The new MSR IA32_SPEC_CTRL MSR was introduced by a recent Intel
microcode updated and can be used by OSes to mitigate
CVE-2017-5715. Unfortunately we can't change the existing CPU
models without breaking existing setups, so users need to
explicitly update their VM configuration to use the new *-IBRS
CPU model if they want to expose IBRS to guests.
The new CPU models are simple copies of the existing CPU models,
with just CPUID_7_0_EDX_SPEC_CTRL added and model_id updated.
Backports commit 61efbbf869293f1deb9ee39d44bd4e635de59fa7 from qemu
Add the new feature word and the "ibpb" feature flag.
Based on a patch by Paolo Bonzini.
Backports commit 1ade973f5202404e772aae7b1acd331270d246dc from qemu
It is valid to have a 48-character model ID on CPUID, however the
definition of X86CPUDefinition::model_id is char[48], which can
make the compiler drop the null terminator from the string.
If a CPU model happens to have 48 bytes on model_id, "-cpu help"
will print garbage and the object_property_set_str() call at
x86_cpu_load_def() will read data outside the model_id array.
We could increase the array size to 49, but this would mean the
compiler would not issue a warning if a 49-char string is used by
mistake for model_id.
To make things simpler, simply change model_id to be const char*,
and validate the string length using an assert() on
x86_register_cpudef_type().
Backports commit 4b220d88ba76fb2623ce4b8ba1f1eea66b82144e from qemu
Add a new base CPU model called 'EPYC' to model processors from AMD EPYC
family (which includes EPYC 76xx,75xx,74xx, 73xx and 72xx).
The following features bits have been added/removed compare to Opteron_G5
Added: monitor, movbe, rdrand, mmxext, ffxsr, rdtscp, cr8legacy, osvw,
fsgsbase, bmi1, avx2, smep, bmi2, rdseed, adx, smap, clfshopt, sha
xsaveopt, xsavec, xgetbv1, arat
Removed: xop, fma4, tbm
Backports commit 2e2efc7dbe2b0adc1200b5aa286cdbed729f6751 from qemu
Introduce Skylake-Server cpu mode which inherits the features from
Skylake-Client and supports some additional features that are: AVX512,
CLWB and PGPE1GB.
Backports commit 53f9a6f45fb214540cb40af45efc11ac40ac454c from qemu
Currently when running KVM, we expose "KVMKVMKVM\0\0\0" in
the 0x40000000 CPUID leaf. Other hypervisors (VMWare,
HyperV, Xen, BHyve) all do the same thing, which leaves
TCG as the odd one out.
The CPUID signature is used by software to detect which
virtual environment they are running in and (potentially)
change behaviour in certain ways. For example, systemd
supports a ConditionVirtualization= setting in unit files.
The virt-what command can also report the virt type it is
running on
Currently both these apps have to resort to custom hacks
like looking for 'fw-cfg' entry in the /proc/device-tree
file to identify TCG.
This change thus proposes a signature "TCGTCGTCGTCG" to be
reported when running under TCG.
To hide this, the -cpu option tcg-cpuid=off can be used.
Backports commits 4ed3d478c63dc65a02eba774c35116618ea5ff10 and 1ce36bfe6424243082d3d7c2330e1a0a4ff72a43 from qemu
This speeds up SMM switches. Later on it may remove the need to take
the BQL, and it may also allow to reuse code between TCG and KVM.
Backports commit f8c45c6550b9ff1e1f0b92709ff3213a79870879 from qemu
The existing code for "host" and "max" CPU models overrides every
single feature in the CPU object at realize time, even the ones
that were explicitly enabled or disabled by the user using
"feat=on" or "feat=off", while features set using +feat/-feat are
kept.
This means "-cpu host,+invtsc" works as expected, while
"-cpu host,invtsc=on" doesn't.
This was a known bug, already documented in a comment inside
x86_cpu_expand_features(). What makes this bug worse now is that
libvirt 3.0.0 and newer now use "feat=on|off" instead of
+feat/-feat when it detects a QEMU version that supports it (see
libvirt commit d47db7b16dd5422c7e487c8c8ee5b181a2f9cd66).
Change the feature property getter/setter to set a
env->user_features field, to keep track of features that were
explicitly changed using QOM properties. Then make the
max_features code not override user features when handling "-cpu
host" and "-cpu max".
This will also allow us to remove the plus_features/minus_features
hack in the future, but I plan to do that after 2.9.0 is
released.
Backports commit d4a606b38b5d4b3689b86cc1575908e82179ecfb from qemu
glibc blacklists TSX on Haswell CPUs with model==60 and
stepping < 4. To make the Haswell CPU model more useful, make
those guests actually use TSX by changing CPU stepping to 4.
References:
* glibc commit 2702856bf45c82cf8e69f2064f5aa15c0ceb6359
https://sourceware.org/git/?p=glibc.git;a=commit;h=2702856bf45c82cf8e69f2064f5aa15c0ceb6359
Backports commit ec56a4a7b07e2943f49da273a31e3195083b1f2e from qemu
Helper function for code that needs to check the host CPU
vendor/family/model/stepping values.
Backports commit 20271d484069f154fb262507e63adc3a37e885d2 from qemu
CPU runnability checks and CPU model expansion have slightly
different requirements. Document the steps involved in loading a
CPU model and realizing a CPU, so their requirements and purpose
are clearly defined.
This patch doesn't change any implementation. It just add
comments, rename the x86_cpu_load_features() function for clarity
(so it won't be confused with x86_cpu_load_def()), and move
x86_cpu_filter_features() closer to it.
Backports commit b8d834a00fa3ed4dad7d371e1a00938a126a54a0 from qemu
This makes qemu_strtosz(), qemu_strtosz_mebi() and
qemu_strtosz_metric() similar to qemu_strtoi64(), except negative
values are rejected.
Backports commit f17fd4fdf0df3d2f3444399d04c38d22b9a3e1b7 from qemu
Change the qemu_strtosz() & friends to return -EINVAL when @endptr is
null and the conversion doesn't consume the string completely.
Matches how qemu_strtol() & friends work.
Only test_qemu_strtosz_simple() passes a null @endptr. No functional
change there, because its conversion consumes the string.
Simplify callers that use @endptr only to fail when it doesn't point
to '\0' to pass a null @endptr instead.
Backports commit 4fcdf65ae2c00ae69f7625f26ed41f37d77b403c from qemu
To parse numbers with metric suffixes, we use
qemu_strtosz_suffix_unit(nptr, &eptr, QEMU_STRTOSZ_DEFSUFFIX_B, 1000)
Capture this in a new function for legibility:
qemu_strtosz_metric(nptr, &eptr)
Replace test_qemu_strtosz_suffix_unit() by test_qemu_strtosz_metric().
Rename qemu_strtosz_suffix_unit() to do_strtosz() and give it internal
linkage.
Backports commit d2734d2629266006b0413433778474d5801c60be from qemu
When CPU vendor is set to AMD, the AMD feature alias bits on
CPUID[0x80000001].EDX are already automatically copied from CPUID[1].EDX
on x86_cpu_realizefn(). When CPU vendor is Intel, those bits are
reserved and should be zero. On either case, those bits shouldn't be set
in the CPU model table.
Commit 726a8ff68677d8d5fba17eb0ffb85076bfb598dc removed those
bits from most CPU models, but the Opteron_* entries still have
them. Remove the alias bits from Opteron_* too.
Add an assert() to x86_register_cpudef_type() to ensure we don't
make the same mistake again.
Backports commit 2a923a293df95334fa22634016efdd138f49da7f from qemu
AVX512_VPOPCNTDQ: Vector POPCNT instructions for word and qwords.
variable precision.
Backports commit f77543772dcd38fa438470d9b80bafbd3a3ebbd7 from qemu
We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.
Backports commit fcf5ef2ab52c621a4617ebbef36bf43b4003f4c0 from qemu
