Commit c8770e7b authored by Avi Kivity's avatar Avi Kivity Committed by Marcelo Tosatti
Browse files

KVM: VMX: Fix host userspace gsbase corruption 



We now use load_gs_index() to load gs safely; unfortunately this also
changes MSR_KERNEL_GS_BASE, which we managed separately.  This resulted
in confusion and breakage running 32-bit host userspace on a 64-bit kernel.

Fix by
- saving guest MSR_KERNEL_GS_BASE before we we reload the host's gs
- doing the host save/load unconditionally, instead of only when in guest
  long mode

Things can be cleaned up further, but this is the minmal fix for now.

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 0a77fe4c

arch/x86/kvm/vmx.c

+7 −8
Original line number Original line Diff line number Diff line
@@ -821,10 +821,9 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) 
#endif

#endif





#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_64

	if (is_long_mode(&vmx->vcpu)) {

	rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);

	rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);

	if (is_long_mode(&vmx->vcpu))

		wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);

		wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);

	}

#endif

#endif

	for (i = 0; i < vmx->save_nmsrs; ++i)

	for (i = 0; i < vmx->save_nmsrs; ++i)

		kvm_set_shared_msr(vmx->guest_msrs[i].index,

		kvm_set_shared_msr(vmx->guest_msrs[i].index,
@@ -839,11 +838,14 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx) 




	++vmx->vcpu.stat.host_state_reload;

	++vmx->vcpu.stat.host_state_reload;

	vmx->host_state.loaded = 0;

	vmx->host_state.loaded = 0;

#ifdef CONFIG_X86_64

	if (is_long_mode(&vmx->vcpu))

		rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);

#endif

	if (vmx->host_state.gs_ldt_reload_needed) {

	if (vmx->host_state.gs_ldt_reload_needed) {

		kvm_load_ldt(vmx->host_state.ldt_sel);

		kvm_load_ldt(vmx->host_state.ldt_sel);

#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_64

		load_gs_index(vmx->host_state.gs_sel);

		load_gs_index(vmx->host_state.gs_sel);

		wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);

#else

#else

		loadsegment(gs, vmx->host_state.gs_sel);

		loadsegment(gs, vmx->host_state.gs_sel);

#endif

#endif
@@ -852,10 +854,7 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx) 
		loadsegment(fs, vmx->host_state.fs_sel);

		loadsegment(fs, vmx->host_state.fs_sel);

	reload_tss();

	reload_tss();

#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_64

	if (is_long_mode(&vmx->vcpu)) {

		rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);

	wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);

	wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);

	}

#endif

#endif

	if (current_thread_info()->status & TS_USEDFPU)

	if (current_thread_info()->status & TS_USEDFPU)

		clts();

		clts();

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