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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: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Avi Kivity 2010-11-11 12:37:26 +02:00 committed by Marcelo Tosatti
parent 0a77fe4c18
commit c8770e7ba6
1 changed files with 7 additions and 8 deletions
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15
arch/x86/kvm/vmx.c
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@ -821,10 +821,9 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
#endif
#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);
}
#endif
for (i = 0; i < vmx->save_nmsrs; ++i)
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->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) {
kvm_load_ldt(vmx->host_state.ldt_sel);
#ifdef CONFIG_X86_64
load_gs_index(vmx->host_state.gs_sel);
wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
#else
loadsegment(gs, vmx->host_state.gs_sel);
#endif
@ -852,10 +854,7 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
loadsegment(fs, vmx->host_state.fs_sel);
reload_tss();
#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
if (current_thread_info()->status & TS_USEDFPU)
clts();