x86/kvm/vmx: Don't fetch the TSS base from the GDT (e0c23063) · Commits · 戴 / test

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:

Andy Lutomirski <luto@kernel.org> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

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 */

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