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>
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@ -821,10 +821,9 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
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#endif
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#ifdef CONFIG_X86_64
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if (is_long_mode(&vmx->vcpu)) {
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rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
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rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
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if (is_long_mode(&vmx->vcpu))
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wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
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}
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#endif
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for (i = 0; i < vmx->save_nmsrs; ++i)
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kvm_set_shared_msr(vmx->guest_msrs[i].index,
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@ -839,11 +838,14 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
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++vmx->vcpu.stat.host_state_reload;
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vmx->host_state.loaded = 0;
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#ifdef CONFIG_X86_64
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if (is_long_mode(&vmx->vcpu))
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rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
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#endif
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if (vmx->host_state.gs_ldt_reload_needed) {
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kvm_load_ldt(vmx->host_state.ldt_sel);
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#ifdef CONFIG_X86_64
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load_gs_index(vmx->host_state.gs_sel);
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wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
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#else
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loadsegment(gs, vmx->host_state.gs_sel);
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#endif
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@ -852,10 +854,7 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
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loadsegment(fs, vmx->host_state.fs_sel);
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reload_tss();
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#ifdef CONFIG_X86_64
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if (is_long_mode(&vmx->vcpu)) {
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rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
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wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
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}
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wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
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#endif
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if (current_thread_info()->status & TS_USEDFPU)
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clts();
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