Messages in this thread |  | | Subject | Re: [PATCH v4 1/3] KVM: x86: add support for user wait instructions | From | Tao Xu <> | Date | Wed, 19 Jun 2019 15:01:38 +0800 |
| |
On 6/19/2019 2:23 PM, Xiaoyao Li wrote: > > > On 6/19/2019 2:09 PM, Tao Xu wrote: >> 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 behavior of user wait instructions in VMX non-root operation is >> determined first by the setting of the "enable user wait and pause" >> secondary processor-based VM-execution control bit 26. >> If the VM-execution control is 0, UMONITOR/UMWAIT/TPAUSE cause >> an invalid-opcode exception (#UD). >> If the VM-execution control is 1, treatment is based on the >> setting of the “RDTSC exiting” VM-execution control. Because KVM never >> enables RDTSC exiting, 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. If >> IA32_UMWAIT_CONTROL[31:2] is zero, the virtual delay is the value in >> EDX:EAX minus the value that RDTSC would return; if >> IA32_UMWAIT_CONTROL[31:2] is not zero, the virtual delay is the minimum >> of that difference and AND(IA32_UMWAIT_CONTROL,FFFFFFFCH). >> >> 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. >> >> Detailed information about user wait instructions can be found in the >> latest Intel 64 and IA-32 Architectures Software Developer's Manual. >> >> Co-developed-by: Jingqi Liu <jingqi.liu@intel.com> >> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com> >> Signed-off-by: Tao Xu <tao3.xu@intel.com> >> --- >> >> no changes in v4. >> --- >> arch/x86/include/asm/vmx.h | 1 + >> arch/x86/kvm/cpuid.c | 2 +- >> arch/x86/kvm/vmx/capabilities.h | 6 ++++++ >> arch/x86/kvm/vmx/vmx.c | 4 ++++ >> 4 files changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h >> index a39136b0d509..8f00882664d3 100644 >> --- a/arch/x86/include/asm/vmx.h >> +++ b/arch/x86/include/asm/vmx.h >> @@ -69,6 +69,7 @@ >> #define SECONDARY_EXEC_PT_USE_GPA 0x01000000 >> #define SECONDARY_EXEC_MODE_BASED_EPT_EXEC 0x00400000 >> #define SECONDARY_EXEC_TSC_SCALING 0x02000000 >> +#define SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE 0x04000000 >> #define PIN_BASED_EXT_INTR_MASK 0x00000001 >> #define PIN_BASED_NMI_EXITING 0x00000008 >> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c >> index e18a9f9f65b5..48bd851a6ae5 100644 >> --- a/arch/x86/kvm/cpuid.c >> +++ b/arch/x86/kvm/cpuid.c >> @@ -405,7 +405,7 @@ static inline int __do_cpuid_ent(struct >> kvm_cpuid_entry2 *entry, u32 function, >> F(AVX512VBMI) | F(LA57) | F(PKU) | 0 /*OSPKE*/ | >> F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) | >> F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) | >> - F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B); >> + F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/; >> /* cpuid 7.0.edx*/ >> const u32 kvm_cpuid_7_0_edx_x86_features = >> diff --git a/arch/x86/kvm/vmx/capabilities.h >> b/arch/x86/kvm/vmx/capabilities.h >> index d6664ee3d127..fd77e17651b4 100644 >> --- a/arch/x86/kvm/vmx/capabilities.h >> +++ b/arch/x86/kvm/vmx/capabilities.h >> @@ -253,6 +253,12 @@ static inline bool cpu_has_vmx_tsc_scaling(void) >> SECONDARY_EXEC_TSC_SCALING; >> } >> +static inline bool vmx_waitpkg_supported(void) >> +{ >> + return vmcs_config.cpu_based_2nd_exec_ctrl & >> + SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE; > > Shouldn't it be > return vmx->secondary_exec_control & > SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE; ?
vmx->secondary_exec_control is another way to get SECONDARY_EXEC_CONTROL but it need to add vmx as input. Use vmcs_config.cpu_based_2nd_exec_ctrl is easy expand to use in other place.
|  |