From 67192a298f5bf98f96e5516c3b6474c49e4853cd Mon Sep 17 00:00:00 2001 From: Tao Xu Date: Fri, 11 Oct 2019 15:41:02 +0800 Subject: [PATCH] x86/cpu: Add support for UMONITOR/UMWAIT/TPAUSE MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Jingqi Liu Signed-off-by: Tao Xu Message-Id: <20191011074103.30393-2-tao3.xu@intel.com> Signed-off-by: Paolo Bonzini --- target/i386/cpu.c | 2 +- target/i386/cpu.h | 2 ++ target/i386/kvm.c | 6 ++++++ 3 files changed, 9 insertions(+), 1 deletion(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 6c87c99487..b635302859 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -1058,7 +1058,7 @@ 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, diff --git a/target/i386/cpu.h b/target/i386/cpu.h index c50a9c7257..112f8670d9 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -731,6 +731,8 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS]; #define CPUID_7_0_ECX_PKU (1U << 3) /* OS Enable Protection Keys */ #define CPUID_7_0_ECX_OSPKE (1U << 4) +/* UMONITOR/UMWAIT/TPAUSE Instructions */ +#define CPUID_7_0_ECX_WAITPKG (1U << 5) /* Additional AVX-512 Vector Byte Manipulation Instruction */ #define CPUID_7_0_ECX_AVX512_VBMI2 (1U << 6) /* Galois Field New Instructions */ diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 49a301190a..94c233943e 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -401,6 +401,12 @@ 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 { + 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.