Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH 02/15] KVM: VMX: Avoid to rdmsrl(MSR_IA32_SYSENTER_ESP) | Date | Thu, 18 Nov 2021 19:08:01 +0800 |
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From: Lai Jiangshan <laijs@linux.alibaba.com>
The value of host MSR_IA32_SYSENTER_ESP is known to be constant for each CPU: (cpu_entry_stack(cpu) + 1) when 32 bit syscall is enabled or NULL is 32 bit syscall is not enabled.
So rdmsrl() can be avoided for the first case and both rdmsrl() and vmcs_writel() can be avoided for the second case.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> --- arch/x86/kvm/vmx/vmx.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 48a34d1a2989..4e4a33226edb 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1271,7 +1271,6 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, if (!already_loaded) { void *gdt = get_current_gdt_ro(); - unsigned long sysenter_esp; /* * Flush all EPTP/VPID contexts, the new pCPU may have stale @@ -1287,8 +1286,11 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, (unsigned long)&get_cpu_entry_area(cpu)->tss.x86_tss); vmcs_writel(HOST_GDTR_BASE, (unsigned long)gdt); /* 22.2.4 */ - rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp); - vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */ + if (IS_ENABLED(CONFIG_IA32_EMULATION) || IS_ENABLED(CONFIG_X86_32)) { + /* 22.2.3 */ + vmcs_writel(HOST_IA32_SYSENTER_ESP, + (unsigned long)(cpu_entry_stack(cpu) + 1)); + } vmx->loaded_vmcs->cpu = cpu; } @@ -4021,6 +4023,8 @@ void vmx_set_constant_host_state(struct vcpu_vmx *vmx) rdmsr(MSR_IA32_SYSENTER_CS, low32, high32); vmcs_write32(HOST_IA32_SYSENTER_CS, low32); + rdmsrl(MSR_IA32_SYSENTER_ESP, tmpl); + vmcs_writel(HOST_IA32_SYSENTER_ESP, tmpl); rdmsrl(MSR_IA32_SYSENTER_EIP, tmpl); vmcs_writel(HOST_IA32_SYSENTER_EIP, tmpl); /* 22.2.3 */ -- 2.19.1.6.gb485710b
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