| Message ID | 20240508154421.61419-1-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | target/i386: remove PCOMMIT from TCG, deprecate property | expand |
On 5/8/24 17:44, Paolo Bonzini wrote: > 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". > > Signed-off-by: Paolo Bonzini<pbonzini@redhat.com> > --- > docs/about/deprecated.rst | 8 ++++++++ > target/i386/cpu.h | 2 -- > target/i386/cpu.c | 2 +- > target/i386/tcg/translate.c | 12 +----------- > 4 files changed, 10 insertions(+), 14 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On Wed, May 08, 2024 at 05:44:21PM +0200, Paolo Bonzini wrote: > Date: Wed, 8 May 2024 17:44:21 +0200 > From: Paolo Bonzini <pbonzini@redhat.com> > Subject: [PATCH] target/i386: remove PCOMMIT from TCG, deprecate property > X-Mailer: git-send-email 2.45.0 > > 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". > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > docs/about/deprecated.rst | 8 ++++++++ > target/i386/cpu.h | 2 -- > target/i386/cpu.c | 2 +- > target/i386/tcg/translate.c | 12 +----------- > 4 files changed, 10 insertions(+), 14 deletions(-) Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 03f8b1b655e..b87fe70be47 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -418,6 +418,14 @@ 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) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/target/i386/cpu.h b/target/i386/cpu.h index 1e0d2c915f5..ccccb62fc35 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -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 */ diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 1058b6803fd..79372de8c5a 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -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) diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index 3842b294842..7d9f6b5c55b 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -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;
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". Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- docs/about/deprecated.rst | 8 ++++++++ target/i386/cpu.h | 2 -- target/i386/cpu.c | 2 +- target/i386/tcg/translate.c | 12 +----------- 4 files changed, 10 insertions(+), 14 deletions(-)