Commit graph

94 commits

Author SHA1 Message Date
Chenyi Qiang d7adcf1d7f target/i386: Add bus lock debug exception support
Bus lock debug exception is a feature that can notify the kernel by
generate an #DB trap after the instruction acquires a bus lock when
CPL>0. This allows the kernel to enforce user application throttling or
mitigations.

This feature is enumerated via CPUID.(EAX=7,ECX=0).ECX[bit 24].

Backports 06e878b413766778a53be3d25c0373a23679d039
2021-03-04 18:50:00 -05:00
Chenyi Qiang 807d541e19 target/i386: Expose VMX entry/exit load pkrs control bits
Expose the VMX exit/entry load pkrs control bits in
VMX_TRUE_EXIT_CTLS/VMX_TRUE_ENTRY_CTLS MSRs to guest, which supports the
PKS in nested VM.

Backports 52a44ad2b92ba4cd81c2b271cd5e4a2d820e91fc
2021-03-04 18:13:36 -05:00
Paolo Bonzini 834e2b2643 target/i86: implement PKS
Protection Keys for Supervisor-mode pages is a simple extension of
the PKU feature that QEMU already implements. For supervisor-mode
pages, protection key restrictions come from a new MSR. The MSR
has no XSAVE state associated to it.

PKS is only respected in long mode. However, in principle it is
possible to set the MSR even outside long mode, and in fact
even the XSAVE state for PKRU could be set outside long mode
using XRSTOR. So do not limit the migration subsections for
PKRU and PKRS to long mode.

Backports e7e7bdababeefff10736c6adf410c66d2f0d46fe
2021-03-04 18:12:44 -05:00
Chetan Pant 3e25486110 x86 tcg cpus: Fix Lesser GPL version number
There is no "version 2" of the "Lesser" General Public License.
It is either "GPL version 2.0" or "Lesser GPL version 2.1".
This patch replaces all occurrences of "Lesser GPL version 2" with
"Lesser GPL version 2.1" in comment section.

Backport d9ff33ada7f32ca59f99b270a2d0eb223b3c9c8f
2021-03-02 13:33:10 -05:00
Chenyi Qiang e5d9e0ed53 target/i386: add fast short REP MOV support
For CPUs support fast short REP MOV[CPUID.(EAX=7,ECX=0):EDX(bit4)], e.g
Icelake and Tigerlake, expose it to the guest VM.

Backports commit 5cb287d2bd578dfe4897458793b4fce35bc4f744 from qemu
2021-02-25 23:31:42 -05:00
Joseph Myers cf54c51869 target/i386: fix IEEE SSE floating-point exception raising
The SSE instruction implementations all fail to raise the expected
IEEE floating-point exceptions because they do nothing to convert the
exception state from the softfloat machinery into the exception flags
in MXCSR.

Fix this by adding such conversions. Unlike for x87, emulated SSE
floating-point operations might be optimized using hardware floating
point on the host, and so a different approach is taken that is
compatible with such optimizations. The required invariant is that
all exceptions set in env->sse_status (other than "denormal operand",
for which the SSE semantics are different from those in the softfloat
code) are ones that are set in the MXCSR; the emulated MXCSR is
updated lazily when code reads MXCSR, while when code sets MXCSR, the
exceptions in env->sse_status are set accordingly.

A few instructions do not raise all the exceptions that would be
raised by the softfloat code, and those instructions are made to save
and restore the softfloat exception state accordingly.

Nothing is done about "denormal operand"; setting that (only for the
case when input denormals are *not* flushed to zero, the opposite of
the logic in the softfloat code for such an exception) will require
custom code for relevant instructions, or else architecture-specific
conditionals in the softfloat code for when to set such an exception
together with custom code for various SSE conversion and rounding
instructions that do not set that exception.

Nothing is done about trapping exceptions (for which there is minimal
and largely broken support in QEMU's emulation in the x87 case and no
support at all in the SSE case).

Backports commit 418b0f93d12a1589d5031405de857844f32e9ccc from qemu
2021-02-25 23:21:32 -05:00
Joseph Myers 2aee4714ab target/i386: reimplement f2xm1 using floatx80 operations
The x87 f2xm1 emulation is currently based around conversion to
double. This is inherently unsuitable for a good emulation of any
floatx80 operation, even before considering that it is a particularly
naive implementation using double (computing with pow and then
subtracting 1 rather than attempting a better emulation using expm1).

Reimplement using the soft-float operations, including additions and
multiplications with higher precision where appropriate to limit
accumulation of errors. I considered reusing some of the m68k code
for transcendental operations, but the instructions don't generally
correspond exactly to x87 operations (for example, m68k has 2^x and
e^x - 1, but not 2^x - 1); to avoid possible accumulation of errors
from applying multiple such operations each rounding to floatx80
precision, I wrote a direct implementation of 2^x - 1 instead. It
would be possible in principle to make the implementation more
efficient by doing the intermediate operations directly with
significands, signs and exponents and not packing / unpacking floatx80
format for each operation, but that would make it significantly more
complicated and it's not clear that's worthwhile; the m68k emulation
doesn't try to do that.

A test is included with many randomly generated inputs. The
assumption of the test is that the result in round-to-nearest mode
should always be one of the two closest floating-point numbers to the
mathematical value of 2^x - 1; the implementation aims to do somewhat
better than that (about 70 correct bits before rounding). I haven't
investigated how accurate hardware is.

Backports commit eca30647fc078f4d9ed1b455bd67960f99dbeb7a from qemu
2021-02-25 13:31:13 -05:00
Liran Alon 7373942623 i386/cpu: Store LAPIC bus frequency in CPU structure
No functional change.
This information will be used by following patches.

Backports commit 73b994f6d74ec00a1d78daf4145096ff9f0e2982 from qemu
2020-06-15 13:00:58 -04:00
Richard Henderson 5ac51ff092 target/i386: Renumber EXCP_SYSCALL
We are not short of numbers for EXCP_*. There is no need to confuse things
by having EXCP_VMEXIT and EXCP_SYSCALL overlap, even though the former is
only used for system mode and the latter is only used for user mode.

Backports commit 628460891dd46c25e33eec01757ac655679ea198 from qemu
2020-04-30 06:56:25 -04:00
Moger, Babu 8c5f623ac3 i386: Add 2nd Generation AMD EPYC processors
Adds the support for 2nd Gen AMD EPYC Processors. The model display
name will be EPYC-Rome.

Adds the following new feature bits on top of the feature bits from the
first generation EPYC models.
perfctr-core : core performance counter extensions support. Enables the VM to
use extended performance counter support. It enables six
programmable counters instead of four counters.
clzero : instruction zeroes out the 64 byte cache line specified in RAX.
xsaveerptr : XSAVE, XSAVE, FXSAVEOPT, XSAVEC, XSAVES always save error
pointers and FXRSTOR, XRSTOR, XRSTORS always restore error
pointers.
wbnoinvd : Write back and do not invalidate cache
ibpb : Indirect Branch Prediction Barrier
amd-stibp : Single Thread Indirect Branch Predictor
clwb : Cache Line Write Back and Retain
xsaves : XSAVES, XRSTORS and IA32_XSS support
rdpid : Read Processor ID instruction support
umip : User-Mode Instruction Prevention support

The Reference documents are available at
https://developer.amd.com/wp-content/resources/55803_0.54-PUB.pdf
https://www.amd.com/system/files/TechDocs/24594.pdf

Depends on following kernel commits:
40bc47b08b6e ("kvm: x86: Enumerate support for CLZERO instruction")
504ce1954fba ("KVM: x86: Expose XSAVEERPTR to the guest")
6d61e3c32248 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
52297436199d ("kvm: svm: Update svm_xsaves_supported")

Backports commit 143c30d4d346831a09e59e9af45afdca0331e819 from qem
2020-04-30 06:50:02 -04:00
Chen Huitao 221333ceaf check arguments, return error instead of raising exceptions. (#1125)
* check arguments, return error instaed of raising exceptions. close #1117.

* remove empty lines. remove thr underscore prefix in function name.

Backports commit 23a426625f1469bd2052eab7d014deb6b9820bf2 from unicorn.
2020-01-14 09:00:11 -05:00
Pan Nengyuan 134a026e6b arm/translate-a64: fix uninitialized variable warning
Fixes:
target/arm/translate-a64.c: In function 'disas_crypto_three_reg_sha512':
target/arm/translate-a64.c:13625:9: error: 'genfn' may be used uninitialized in this function [-Werror=maybe-uninitialized]
genfn(tcg_rd_ptr, tcg_rn_ptr, tcg_rm_ptr);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
qemu/target/arm/translate-a64.c:13609:8: error: 'feature' may be used uninitialized in this function [-Werror=maybe-uninitialized]
if (!feature) {

Backports commit c7a5e7910517e2711215a9e869a733ffde696091 from qemu
2020-01-14 08:46:42 -05:00
Xiaoyao Li 31ab6fbd2c target/i386: Add missed features to Cooperlake CPU model
It lacks VMX features and two security feature bits (disclosed recently) in
MSR_IA32_ARCH_CAPABILITIES in current Cooperlake CPU model, so add them.

Fixes: 22a866b6166d ("i386: Add new CPU model Cooperlake")

Backports commit 2dea9d9ca4ea7e9afe83d0b4153b21a16987e866 from qemu
2020-01-14 08:43:26 -05:00
Xiaoyao Li 5e0b249dc0 target/i386: Add new bit definitions of MSR_IA32_ARCH_CAPABILITIES
The bit 6, 7 and 8 of MSR_IA32_ARCH_CAPABILITIES are recently disclosed
for some security issues. Add the definitions for them to be used by named
CPU models.

Backports commit 6c997b4adb300788d61d72e2b8bc67c03a584956 from qemu
2020-01-14 08:30:17 -05:00
Cathy Zhang 67b6034a0f i386: Add macro for stibp
stibp feature is already added through the following commit.
0e89165829

Add a macro for it to allow CPU models to report it when host supports.

Backports commit 5af514d0cb314f43bc53f2aefb437f6451d64d0c from qemu
2020-01-14 08:00:22 -05:00
Lioncash 067a459774 i386: Backport some formatting changes 2020-01-14 08:00:18 -05:00
Cathy Zhang 8c0ed30d38 i386: Add MSR feature bit for MDS-NO
Define MSR_ARCH_CAP_MDS_NO in the IA32_ARCH_CAPABILITIES MSR to allow
CPU models to report the feature when host supports it.

Backports commit 77b168d221191156c47fcd8d1c47329dfdb9439e from qemu
2020-01-14 07:56:43 -05:00
Jing Liu 61be812bfb
x86: Intel AVX512_BF16 feature enabling
Intel CooperLake cpu adds AVX512_BF16 instruction, defining as
CPUID.(EAX=7,ECX=1):EAX[bit 05].

The patch adds a property for setting the subleaf of CPUID leaf 7 in
case that people would like to specify it.

The release spec link as follows,
https://software.intel.com/sites/default/files/managed/c5/15/\
architecture-instruction-set-extensions-programming-reference.pdf

Backports commit 80db491da4ce8b199e0e8d1e23943b20aab82f69 from qemu
2019-11-18 22:06:57 -05:00
Eduardo Habkost e5e5c2fd6c
i386: Register versioned CPU models
Add support for registration of multiple versions of CPU models.

The existing CPU models will be registered with a "-v1" suffix.

The -noTSX, -IBRS, and -IBPB CPU model variants will become
versions of the original models in a separate patch, so
make sure we register no versions for them.

Backports commit dcafd1ef0af227ef87f7a6dec8fc66d7d2e2442d from qemu
2019-08-08 19:01:35 -04:00
Like Xu 2c424e691c
target/i386: Add CPUID.1F generation support for multi-dies PCMachine
The CPUID.1F as Intel V2 Extended Topology Enumeration Leaf would be
exposed if guests want to emulate multiple software-visible die within
each package. Per Intel's SDM, the 0x1f is a superset of 0xb, thus they
can be generated by almost same code as 0xb except die_offset setting.

If the number of dies per package is greater than 1, the cpuid_min_level
would be adjusted to 0x1f regardless of whether the host supports CPUID.1F.
Likewise, the CPUID.1F wouldn't be exposed if env->nr_dies < 2.

Backports commit a94e1428991f741e2c6636e7c8df7f8d1905d983 from qemu
2019-08-08 18:24:46 -04:00
Lioncash a82e4efa24
i386/cpu: Consolidate die-id validity in smp context
The field die_id (default as 0) and has_die_id are introduced to X86CPU.
Following the legacy smp check rules, the die_id validity is added to
the same contexts as leagcy smp variables such as hmp_hotpluggable_cpus(),
machine_set_cpu_numa_node(), cpu_slot_to_string() and pc_cpu_pre_plug().

Backports relevant bits from 176d2cda0dee9f4f78f604ad72d6a111e8e38f3b
from qemu
2019-08-08 18:14:27 -04:00
Like Xu efd887b992
i386: Add die-level cpu topology to x86CPU on PCMachine
The die-level as the first PC-specific cpu topology is added to the leagcy
cpu topology model, which has one die per package implicitly and only the
numbers of sockets/cores/threads are configurable.

In the new model with die-level support, the total number of logical
processors (including offline) on board will be calculated as:

\#cpus = #sockets * #dies * #cores * #threads

and considering compatibility, the default value for #dies would be
initialized to one in x86_cpu_initfn() and pc_machine_initfn().

Backports commit c26ae610811e8d52f4fc73e3ae0a8bc4a24d6763 from qemu
2019-08-08 18:10:42 -04:00
Xiaoyao Li 576be63f06
target/i386: define a new MSR based feature word - FEAT_CORE_CAPABILITY
MSR IA32_CORE_CAPABILITY is a feature-enumerating MSR, which only
enumerates the feature split lock detection (via bit 5) by now.

The existence of MSR IA32_CORE_CAPABILITY is enumerated by CPUID.7_0:EDX[30].

The latest kernel patches about them can be found here:
https://lkml.org/lkml/2019/4/24/1909

Backports commit 597360c0d8ebda9ca6f239db724a25bddec62b2f from qemu
2019-06-25 18:59:52 -05:00
Richard Henderson 8f53f09a05
cpu: Introduce CPUNegativeOffsetState
Nothing in there so far, but all of the plumbing done
within the target ArchCPU state.

Backports commit 5b146dc716cfd247f99556c04e6e46fbd67565a0 from qemu
2019-06-13 15:08:25 -04:00
Richard Henderson ac176ccb38
cpu: Move ENV_OFFSET to exec/gen-icount.h
Now that we have ArchCPU, we can define this generically,
in the one place that needs it.

Backports commit 677c4d69ac21961e76a386f9bfc892a44923acc0 from qemu
2019-06-12 12:20:21 -04:00
Richard Henderson 187778c781
target/i386: Use env_cpu, env_archcpu
Cleanup in the boilerplate that each target must define.
Replace x86_env_get_cpu with env_archcpu. The combination
CPU(x86_env_get_cpu) should have used ENV_GET_CPU to begin;
use env_cpu now.

Backports commit 6aa9e42f27331be34e06d4d66f92f2272868f96a from qemu
2019-06-12 11:46:35 -04:00
Richard Henderson fbf91a6535
cpu: Replace ENV_GET_CPU with env_cpu
Now that we have both ArchCPU and CPUArchState, we can define
this generically instead of via macro in each target's cpu.h.

Backports commit 29a0af618ddd21f55df5753c3e16b0625f534b3c from qemu
2019-06-12 11:16:16 -04:00
Richard Henderson ae94fb5992
cpu: Define ArchCPU
For all targets, do this just before including exec/cpu-all.h.

Backports commit 2161a612b4e1d388046320bc464adefd6bba01a0 from qemu
2019-06-12 11:08:39 -04:00
Richard Henderson e3f1f25996
cpu: Define CPUArchState with typedef
For all targets, do this just before including exec/cpu-all.h.

Backports commit 4f7c64b3819d559417615ed2b1d028ebc1a49580 from qemu
2019-06-12 11:06:36 -04:00
Richard Henderson df2a890bd7
tcg: Split out target/arch/cpu-param.h
For all targets, into this new file move TARGET_LONG_BITS,
TARGET_PAGE_BITS, TARGET_PHYS_ADDR_SPACE_BITS,
TARGET_VIRT_ADDR_SPACE_BITS, and NB_MMU_MODES.

Include this new file from exec/cpu-defs.h.

This now removes the somewhat odd requirement that target/arch/cpu.h
defines TARGET_LONG_BITS before including exec/cpu-defs.h, so push the
bulk of the includes within target/arch/cpu.h to the top.

Backports commit 74433bf083b0766aba81534f92de13194f23ff3e from qemu
2019-06-10 19:35:46 -04:00
Wanpeng Li b41364fdc5
i386: Enable IA32_MISC_ENABLE MWAIT bit when exposing mwait/monitor
The CPUID.01H:ECX[bit 3] ought to mirror the value of the MSR
IA32_MISC_ENABLE MWAIT bit and as userspace has control of them
both, it is userspace's job to configure both bits to match on
the initial setup.

Backports commit 4cfd7bab3f5564f6c1a23b06f73d5aa2f957cd16 from qemu
2019-06-04 13:17:43 -04:00
Richard Henderson fe9ac6e1c4
target/i386: Convert to CPUClass::tlb_fill
We do not support probing, but we do not need it yet either.

Backports commit 5d0044212c375c0696baef7bba13699277dac5b5 from qemu
2019-05-16 17:08:14 -04:00
Pu Wen 4bbf02a5f6
i386: Add new Hygon 'Dhyana' CPU model
Add a new base CPU model called 'Dhyana' to model processors from Hygon
Dhyana(family 18h), which derived from AMD EPYC(family 17h).

The following features bits have been removed compare to AMD EPYC:
aes, pclmulqdq, sha_ni

The Hygon Dhyana support to KVM in Linux is already accepted upstream[1].
So add Hygon Dhyana support to Qemu is necessary to create Hygon's own
CPU model.

Reference:
[1] https://git.kernel.org/tip/fec98069fb72fb656304a3e52265e0c2fc9adf87

Backports commit 8d031cec366f26669807eb43f61eb335973b7053 from qemu
2019-04-30 09:13:55 -04:00
Luwei Kang 9f2ce63414
i386: extended the cpuid_level when Intel PT is enabled
Intel Processor Trace required CPUID[0x14] but the cpuid_level
have no change when create a kvm guest with
e.g. "-cpu qemu64,+intel-pt

Backports relevant bits of commit
f24c3a79a415042f6dc195f029a2ba7247d14cac from qemu
2019-03-11 16:40:23 -04:00
dmarxn 7164ab5ff4
changed cpu_compue_eflags to use the updated eflags variable. Otherwise, cli/sti and popfl may break, as we get the non-updated eflags (#1057)
Backports commit 360e9c60e1feb4a93e7e43f30858e38eac2d35f2 from unicorn
2019-02-28 17:05:13 -05:00
Robert Hoo c8a49d8593
Revert "i386: Add CPUID bit for PCONFIG"
This reverts commit 5131dc433df54b37e8e918d8fba7fe10344e7a7b.
For new instruction 'PCONFIG' will not be exposed to guest.

Backports commit 712f807e1965c8f1f1da5bbec2b92a8c540e6631 from qemu
2019-02-07 08:56:40 -05:00
Lioncash 29d84a9296
target: Resolve repeated typedef warnings 2019-01-22 20:27:35 -05:00
Vitaly Kuznetsov 2873612479
i386/kvm: expose HV_CPUID_ENLIGHTMENT_INFO.EAX and HV_CPUID_NESTED_FEATURES.EAX as feature words
It was found that QMP users of QEMU (e.g. libvirt) may need
HV_CPUID_ENLIGHTMENT_INFO.EAX/HV_CPUID_NESTED_FEATURES.EAX information. In
particular, 'hv_tlbflush' and 'hv_evmcs' enlightenments are only exposed in
HV_CPUID_ENLIGHTMENT_INFO.EAX.

HV_CPUID_NESTED_FEATURES.EAX is exposed for two reasons: convenience
(we don't need to export it from hyperv_handle_properties() and as
future-proof for Enlightened MSR-Bitmap, PV EPT invalidation and
direct virtual flush features.

Backports commit a2b107dbbd342ff2077aa5af705efaf68c375459 from qemu
2019-01-14 15:01:13 -05:00
Eduardo Habkost 3eb700bec7
x86: host-phys-bits-limit option
Backports part of commit 258fe08bd341d2e230676228307294e41f33002c from
qemu. Namely, just adding the struct member.
2019-01-14 14:56:57 -05:00
Liu Jingqi 10d7f18674
x86/cpu: Enable MOVDIR64B cpu feature
MOVDIR64B moves 64-bytes as direct-store with 64-bytes write atomicity.
Direct store is implemented by using write combining (WC) for writing
data directly into memory without caching the data.

The bit definition:
CPUID.(EAX=7,ECX=0):ECX[bit 28] MOVDIR64B

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 1c65775ffc2dbd276a8bffe592feba0e186a151c from qemu
2018-12-18 03:48:19 -05:00
Liu Jingqi 6aa3cd24fd
x86/cpu: Enable MOVDIRI cpu feature
MOVDIRI moves doubleword or quadword from register to memory through
direct store which is implemented by using write combining (WC) for
writing data directly into memory without caching the data.

The bit definition:
CPUID.(EAX=7,ECX=0):ECX[bit 27] MOVDIRI

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 24261de4916596d8ab5f5fee67e9e7a19e8325a5 from qemu
2018-12-18 03:46:49 -05:00
Robert Hoo 24733280b2
x86: define a new MSR based feature word -- FEATURE_WORDS_ARCH_CAPABILITIES
Note RSBA is specially treated -- no matter host support it or not, qemu
pretends it is supported.

Backports commit d86f963694df27f11b3681ffd225c9362de1b634 from qemu
2018-11-11 08:07:33 -05:00
Paolo Bonzini 752aea8379
target/i386: rename HF_SVMI_MASK to HF_GUEST_MASK
This flag will be used for KVM's nested VMX migration; the HF_GUEST_MASK name
is already used in KVM, adopt it in QEMU as well.

Backports commit f8dc4c645ec2956a6cd97e0ca0fdd4753181f735 from qemu
2018-10-04 04:24:39 -04:00
Paolo Bonzini 0bc0ff320c
target/i386: unify masking of interrupts
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
2018-10-04 04:19:57 -04:00
Andrew Dutcher 81f8a1be80
eflags patch
Preserves EFLAGS across basic blocks.

Reapplies commit 3a1f231e8f from qemu
2018-09-07 22:01:24 -04:00
Paolo Bonzini 85303e3caf
target/i386: update MPX flags when CPL changes
Backports commit 5e76d84e690954d79af357fafb1903113a00b32e from qemu
2018-08-25 03:32:22 -04:00
Robert Hoo 0e16ff259b
i386: Add CPUID bit for WBNOINVD
WBNOINVD: Write back and do not invalidate cache, enumerated by
CPUID.(EAX=80000008H, ECX=0):EBX[bit 9].

Backports commit 59a80a19ca31a6fff9fdbb6b4cf55a5a0767c3bc from qemu
2018-08-17 14:29:10 -04:00
Robert Hoo 8b59666ae6
i386: Add CPUID bit for PCONFIG
PCONFIG: Platform configuration, enumerated by CPUID.(EAX=07H, ECX=0):
EDX[bit18].

Backports commit 5131dc433df54b37e8e918d8fba7fe10344e7a7b from qemu
2018-08-17 14:28:11 -04:00
Robert Hoo 44e0a97e0b
i386: Add CPUID bit and feature words for IA32_ARCH_CAPABILITIES MSR
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
2018-08-17 14:27:28 -04:00
Robert Hoo b3fccc4841
i386: Add new MSR indices for IA32_PRED_CMD and IA32_ARCH_CAPABILITIES
IA32_PRED_CMD MSR gives software a way to issue commands that affect the state
of indirect branch predictors. Enumerated by CPUID.(EAX=7H,ECX=0):EDX[26].
IA32_ARCH_CAPABILITIES MSR enumerates architectural features of RDCL_NO and
IBRS_ALL. Enumerated by CPUID.(EAX=07H, ECX=0):EDX[29].

https://software.intel.com/sites/default/files/managed/c5/63/336996-Speculative-Execution-Side-Channel-Mitigations.pdf

Backports commit 8c80c99fcceabd0708a5a83f08577e778c9419f5 from qemu
2018-08-17 14:26:10 -04:00