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KVM: VMX: Fix host userspace gsbase corruption

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commit c8770e7ba6 upstream.

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>
[bwh: Backport to 2.6.32]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Ben Hutchings 2010-11-29 13:00:15 -02:00 committed by Greg Kroah-Hartman
parent 91445a8f6f
commit fda45f0be5
1 changed files with 11 additions and 5 deletions
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16
arch/x86/kvm/vmx.c
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@ -654,10 +654,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
#endif
#ifdef CONFIG_X86_64
if (is_long_mode(&vmx->vcpu))
save_msrs(vmx->host_msrs +
vmx->msr_offset_kernel_gs_base, 1);
save_msrs(vmx->host_msrs + vmx->msr_offset_kernel_gs_base, 1);
#endif
load_msrs(vmx->guest_msrs, vmx->save_nmsrs);
load_transition_efer(vmx);
@ -672,17 +669,26 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
vmx->host_state.loaded = 0;
if (vmx->host_state.fs_reload_needed)
loadsegment(fs, vmx->host_state.fs_sel);
#ifdef CONFIG_X86_64
if (is_long_mode(&vmx->vcpu))
save_msrs(vmx->guest_msrs + vmx->msr_offset_kernel_gs_base, 1);
#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
}
reload_tss();
#ifdef CONFIG_X86_64
save_msrs(vmx->guest_msrs, vmx->msr_offset_kernel_gs_base);
save_msrs(vmx->guest_msrs + vmx->msr_offset_kernel_gs_base + 1,
vmx->save_nmsrs - vmx->msr_offset_kernel_gs_base - 1);
#else
save_msrs(vmx->guest_msrs, vmx->save_nmsrs);
#endif
load_msrs(vmx->host_msrs, vmx->save_nmsrs);
reload_host_efer(vmx);
load_gdt(&__get_cpu_var(host_gdt));