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target/i386: remove PCOMMIT from TCG, deprecate property 

The PCOMMIT instruction was never included in any physical processor.
TCG implements it as a no-op instruction, but its utility is debatable
to say the least.  Drop it from the decoder since it is only available
with "-cpu max", which does not guarantee migration compatibility
across versions, and deprecate the property just in case someone is
using it as "pcommit=off".

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-05-08 17:44:12 +02:00
parent dafec285bd
commit 9f07e47a5e
4 changed files with 10 additions and 14 deletions
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8
docs/about/deprecated.rst
View File

@ -432,6 +432,14 @@ Backend ``memory`` (since 9.0)
CPU device properties
'''''''''''''''''''''
``pcommit`` on x86 (since 9.1)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The PCOMMIT instruction was never included in any physical processor.
It was implemented as a no-op instruction in TCG up to QEMU 9.0, but
only with ``-cpu max`` (which does not guarantee migration compatibility
across versions).
``pmu-num=n`` on RISC-V CPUs (since 8.2)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

2
target/i386/cpu.c
View File

@ -713,7 +713,7 @@ void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
#endif
#define TCG_7_0_EBX_FEATURES (CPUID_7_0_EBX_SMEP | CPUID_7_0_EBX_SMAP | \
CPUID_7_0_EBX_BMI1 | CPUID_7_0_EBX_BMI2 | CPUID_7_0_EBX_ADX | \
CPUID_7_0_EBX_PCOMMIT | CPUID_7_0_EBX_CLFLUSHOPT | \
CPUID_7_0_EBX_CLFLUSHOPT | \
CPUID_7_0_EBX_CLWB | CPUID_7_0_EBX_MPX | CPUID_7_0_EBX_FSGSBASE | \
CPUID_7_0_EBX_ERMS | CPUID_7_0_EBX_AVX2 | CPUID_7_0_EBX_RDSEED | \
CPUID_7_0_EBX_SHA_NI | CPUID_7_0_EBX_KERNEL_FEATURES)

2
target/i386/cpu.h
View File

@ -816,8 +816,6 @@ uint64_t x86_cpu_get_supported_feature_word(FeatureWord w,
#define CPUID_7_0_EBX_SMAP (1U << 20)
/* AVX-512 Integer Fused Multiply Add */
#define CPUID_7_0_EBX_AVX512IFMA (1U << 21)
/* Persistent Commit */
#define CPUID_7_0_EBX_PCOMMIT (1U << 22)
/* Flush a Cache Line Optimized */
#define CPUID_7_0_EBX_CLFLUSHOPT (1U << 23)
/* Cache Line Write Back */

12
target/i386/tcg/translate.c
View File

@ -4487,17 +4487,7 @@ static void disas_insn_old(DisasContext *s, CPUState *cpu, int b)
}
goto unknown_op;
case 0xf8: /* sfence / pcommit */
if (prefixes & PREFIX_DATA) {
/* pcommit */
if (!(s->cpuid_7_0_ebx_features & CPUID_7_0_EBX_PCOMMIT)
|| (prefixes & PREFIX_LOCK)) {
goto illegal_op;
}
break;
}
/* fallthru */
case 0xf9 ... 0xff: /* sfence */
case 0xf8 ... 0xff: /* sfence */
if (!(s->cpuid_features & CPUID_SSE)
|| (prefixes & PREFIX_LOCK)) {
goto illegal_op;