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x86/kvm/vmx: read MSR_{FS,KERNEL_GS}_BASE from current->thread

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vmx_save_host_state() is only called from kvm_arch_vcpu_ioctl_run() so
the context is pretty well defined. Read MSR_{FS,KERNEL_GS}_BASE from
current->thread after calling save_fsgs() which takes care of
X86_BUG_NULL_SEG case now and will do RD[FG,GS]BASE when FSGSBASE
extensions are exposed to userspace (currently they are not).

Acked-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov
2018-03-13 18:48:04 +01:00
committed by Paolo Bonzini
parent b31c114b82
commit 42b933b597
3 changed files with 29 additions and 3 deletions
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13
arch/x86/kvm/vmx.c
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@@ -2165,7 +2165,15 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
*/
vmx->host_state.ldt_sel = kvm_read_ldt();
vmx->host_state.gs_ldt_reload_needed = vmx->host_state.ldt_sel;
#ifdef CONFIG_X86_64
save_fsgs_for_kvm();
vmx->host_state.fs_sel = current->thread.fsindex;
vmx->host_state.gs_sel = current->thread.gsindex;
#else
savesegment(fs, vmx->host_state.fs_sel);
savesegment(gs, vmx->host_state.gs_sel);
#endif
if (!(vmx->host_state.fs_sel & 7)) {
vmcs_write16(HOST_FS_SELECTOR, vmx->host_state.fs_sel);
vmx->host_state.fs_reload_needed = 0;
@@ -2173,7 +2181,6 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
vmcs_write16(HOST_FS_SELECTOR, 0);
vmx->host_state.fs_reload_needed = 1;
}
savesegment(gs, vmx->host_state.gs_sel);
if (!(vmx->host_state.gs_sel & 7))
vmcs_write16(HOST_GS_SELECTOR, vmx->host_state.gs_sel);
else {
@@ -2187,7 +2194,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
#endif
#ifdef CONFIG_X86_64
vmcs_writel(HOST_FS_BASE, read_msr(MSR_FS_BASE));
vmcs_writel(HOST_FS_BASE, current->thread.fsbase);
vmcs_writel(HOST_GS_BASE, read_msr(MSR_GS_BASE));
#else
vmcs_writel(HOST_FS_BASE, segment_base(vmx->host_state.fs_sel));
@@ -2195,7 +2202,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu)
#endif
#ifdef CONFIG_X86_64
rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
vmx->msr_host_kernel_gs_base = current->thread.gsbase;
if (is_long_mode(&vmx->vcpu))
wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
#endif