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author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2018-03-13 18:48:04 +0100 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-03-16 22:03:53 +0100 |
commit | 42b933b59721f288e3ce23ca79a17a973808dab9 (patch) | |
tree | 24f455d30d65833ac4eb2d00a2029f09519aa5aa /arch/x86 | |
parent | b31c114b82b2b55913d2cf744e6a665c2ca090ac (diff) | |
download | linux-stable-42b933b59721f288e3ce23ca79a17a973808dab9.tar.gz linux-stable-42b933b59721f288e3ce23ca79a17a973808dab9.tar.bz2 linux-stable-42b933b59721f288e3ce23ca79a17a973808dab9.zip |
x86/kvm/vmx: read MSR_{FS,KERNEL_GS}_BASE from current->thread
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>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/include/asm/processor.h | 5 | ||||
-rw-r--r-- | arch/x86/kernel/process_64.c | 14 | ||||
-rw-r--r-- | arch/x86/kvm/vmx.c | 13 |
3 files changed, 29 insertions, 3 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index b0ccd4847a58..1d816a3325a1 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -410,6 +410,11 @@ DECLARE_INIT_PER_CPU(irq_stack_union); DECLARE_PER_CPU(char *, irq_stack_ptr); DECLARE_PER_CPU(unsigned int, irq_count); extern asmlinkage void ignore_sysret(void); + +#if IS_ENABLED(CONFIG_KVM) +/* Save actual FS/GS selectors and bases to current->thread */ +void save_fsgs_for_kvm(void); +#endif #else /* X86_64 */ #ifdef CONFIG_CC_STACKPROTECTOR /* diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 9eb448c7859d..4b100fe0f508 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -205,6 +205,20 @@ static __always_inline void save_fsgs(struct task_struct *task) save_base_legacy(task, task->thread.gsindex, GS); } +#if IS_ENABLED(CONFIG_KVM) +/* + * While a process is running,current->thread.fsbase and current->thread.gsbase + * may not match the corresponding CPU registers (see save_base_legacy()). KVM + * wants an efficient way to save and restore FSBASE and GSBASE. + * When FSGSBASE extensions are enabled, this will have to use RD{FS,GS}BASE. + */ +void save_fsgs_for_kvm(void) +{ + save_fsgs(current); +} +EXPORT_SYMBOL_GPL(save_fsgs_for_kvm); +#endif + static __always_inline void loadseg(enum which_selector which, unsigned short sel) { diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 12473e769b0d..0cbdd4cf9ba0 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -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 |