UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions. This patch adds support for user wait instructions in KVM. Availability of the user wait instructions is indicated by the presence of the CPUID feature flag WAITPKG CPUID.0x07.0x0:ECX[5]. User wait instructions may be executed at any privilege level, and use IA32_UMWAIT_CONTROL MSR to set the maximum time. The patch enable the umonitor, umwait and tpause features in KVM. Because umwait and tpause can put a (psysical) CPU into a power saving state, by default we dont't expose it to kvm and enable it only when guest CPUID has it. And use QEMU command-line "-overcommit cpu-pm=on" (enable_cpu_pm is enabled), a VM can use UMONITOR, UMWAIT and TPAUSE instructions. If the instruction causes a delay, the amount of time delayed is called here the physical delay. The physical delay is first computed by determining the virtual delay (the time to delay relative to the VM’s timestamp counter). Otherwise, UMONITOR, UMWAIT and TPAUSE cause an invalid-opcode exception(#UD). The release document ref below link: https://software.intel.com/sites/default/files/\ managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf Co-developed-by: Jingqi Liu <jingqi.liu@xxxxxxxxx> Signed-off-by: Jingqi Liu <jingqi.liu@xxxxxxxxx> Signed-off-by: Tao Xu <tao3.xu@xxxxxxxxx> --- changes in v3: Simplify the patches, expose user wait instructions when the guest has CPUID (Paolo) --- target/i386/cpu.c | 3 ++- target/i386/cpu.h | 1 + target/i386/kvm.c | 4 ++++ 3 files changed, 7 insertions(+), 1 deletion(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index fbed2eb804..0fb86c90db 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -1060,7 +1060,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = { .type = CPUID_FEATURE_WORD, .feat_names = { NULL, "avx512vbmi", "umip", "pku", - NULL /* ospke */, NULL, "avx512vbmi2", NULL, + NULL /* ospke */, "waitpkg", "avx512vbmi2", NULL, "gfni", "vaes", "vpclmulqdq", "avx512vnni", "avx512bitalg", NULL, "avx512-vpopcntdq", NULL, "la57", NULL, NULL, NULL, @@ -5222,6 +5222,7 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp) host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx, &cpu->mwait.ecx, &cpu->mwait.edx); env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR; + env->features[FEAT_7_0_ECX] |= CPUID_7_0_ECX_WAITPKG; } } diff --git a/target/i386/cpu.h b/target/i386/cpu.h index 0732e059ec..2f7c57a3c2 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -670,6 +670,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS]; #define CPUID_7_0_ECX_UMIP (1U << 2) #define CPUID_7_0_ECX_PKU (1U << 3) #define CPUID_7_0_ECX_OSPKE (1U << 4) +#define CPUID_7_0_ECX_WAITPKG (1U << 5) /* UMONITOR/UMWAIT/TPAUSE Instructions */ #define CPUID_7_0_ECX_VBMI2 (1U << 6) /* Additional VBMI Instrs */ #define CPUID_7_0_ECX_GFNI (1U << 8) #define CPUID_7_0_ECX_VAES (1U << 9) diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 6899061b4e..3efdb90f11 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -388,6 +388,10 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, if (host_tsx_blacklisted()) { ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE); } + } else if (function == 7 && index == 0 && reg == R_ECX) { + if (enable_cpu_pm) { + ret |= CPUID_7_0_ECX_WAITPKG; + } } else if (function == 7 && index == 0 && reg == R_EDX) { /* * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM hosts. -- 2.20.1
