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Commit e0c23063 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Paolo Bonzini
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x86/kvm/vmx: Don't fetch the TSS base from the GDT 



The current CPU's TSS base is a foregone conclusion, so there's no need
to parse it out of the segment tables.  This should save a couple cycles
(as STR is surely microcoded and poorly optimized) but, more importantly,
it's a cleanup and it means that segment_base() will never be called on
64-bit kernels.

Cc: Thomas Garnier <thgarnie@google.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4f53ab14

arch/x86/kvm/vmx.c

+4 −10
Original line number Diff line number Diff line
@@ -2086,13 +2086,6 @@ static unsigned long segment_base(u16 selector) 
	return v;

}



static inline unsigned long kvm_read_tr_base(void)

{

	u16 tr;

	asm("str %0" : "=g"(tr));

	return segment_base(tr);

}



static void vmx_save_host_state(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -2292,10 +2285,11 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 


		/*

		 * Linux uses per-cpu TSS and GDT, so set these when switching

		 * processors.

		 * processors.  See 22.2.4.

		 */

		vmcs_writel(HOST_TR_BASE, kvm_read_tr_base()); /* 22.2.4 */

		vmcs_writel(HOST_GDTR_BASE, gdt->address);   /* 22.2.4 */

		vmcs_writel(HOST_TR_BASE,

			    (unsigned long)this_cpu_ptr(&cpu_tss));

		vmcs_writel(HOST_GDTR_BASE, gdt->address);



		rdmsrl(MSR_IA32_SYSENTER_ESP, sysenter_esp);

		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */