Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 35060ed6 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
Browse files

x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE 



vmx_save_host_state() is only called from kvm_arch_vcpu_ioctl_run() so
the context is pretty well defined and as we're past 'swapgs' MSR_GS_BASE
should contain kernel's GS base which we point to irq_stack_union.

Add new kernelmode_gs_base() API, irq_stack_union needs to be exported
as KVM can be build as module.

Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 42b933b5

arch/x86/include/asm/processor.h

+5 −0
Original line number Diff line number Diff line
@@ -407,6 +407,11 @@ union irq_stack_union { 
DECLARE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __visible;

DECLARE_INIT_PER_CPU(irq_stack_union);



static inline unsigned long cpu_kernelmode_gs_base(int cpu)

{

	return (unsigned long)per_cpu(irq_stack_union.gs_base, cpu);

}



DECLARE_PER_CPU(char *, irq_stack_ptr);

DECLARE_PER_CPU(unsigned int, irq_count);

extern asmlinkage void ignore_sysret(void);

arch/x86/kernel/cpu/common.c

+2 −1
Original line number Diff line number Diff line
@@ -487,7 +487,7 @@ void load_percpu_segment(int cpu) 
	loadsegment(fs, __KERNEL_PERCPU);

#else

	__loadsegment_simple(gs, 0);

	wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));

	wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu));

#endif

	load_stack_canary_segment();

}
@@ -1398,6 +1398,7 @@ __setup("clearcpuid=", setup_clearcpuid); 
#ifdef CONFIG_X86_64

DEFINE_PER_CPU_FIRST(union irq_stack_union,

		     irq_stack_union) __aligned(PAGE_SIZE) __visible;

EXPORT_PER_CPU_SYMBOL_GPL(irq_stack_union);



/*

 * The following percpu variables are hot.  Align current_task to

arch/x86/kvm/vmx.c

+2 −1
Original line number Diff line number Diff line
@@ -2153,6 +2153,7 @@ static unsigned long segment_base(u16 selector) 
static void vmx_save_host_state(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	int cpu = raw_smp_processor_id();

	int i;



	if (vmx->host_state.loaded)
@@ -2195,7 +2196,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) 


#ifdef CONFIG_X86_64

	vmcs_writel(HOST_FS_BASE, current->thread.fsbase);

	vmcs_writel(HOST_GS_BASE, read_msr(MSR_GS_BASE));

	vmcs_writel(HOST_GS_BASE, cpu_kernelmode_gs_base(cpu));

#else

	vmcs_writel(HOST_FS_BASE, segment_base(vmx->host_state.fs_sel));

	vmcs_writel(HOST_GS_BASE, segment_base(vmx->host_state.gs_sel));