Re: [PATCH 01/15] KVM: VMX: Use x86 core API to access to fs_base and inactive gs_base

Paolo Bonzini
2021-11-18T16:05:59Z

On 11/18/21 12:08, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
>
> And they use FSGSBASE instructions when enabled.
>
> Cc: x86@kernel.org
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>

This needs ACK from x86 maintainers.

I queued 2-4 and 6-14.

Paolo

> ---
> arch/x86/include/asm/kvm_host.h | 10 ----------
> arch/x86/kernel/process_64.c | 2 ++
> arch/x86/kvm/vmx/vmx.c | 14 +++++++-------
> 3 files changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1fcb345bc107..4cbb402f5636 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1808,16 +1808,6 @@ static inline void kvm_load_ldt(u16 sel)
> asm("lldt %0" : : "rm"(sel));
> }
>
> -#ifdef CONFIG_X86_64
> -static inline unsigned long read_msr(unsigned long msr)
> -{
> - u64 value;
> -
> - rdmsrl(msr, value);
> - return value;
> -}
> -#endif
> -
> static inline void kvm_inject_gp(struct kvm_vcpu *vcpu, u32 error_code)
> {
> kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 3402edec236c..296bd5c2e38b 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -443,6 +443,7 @@ unsigned long x86_gsbase_read_cpu_inactive(void)
>
> return gsbase;
> }
> +EXPORT_SYMBOL_GPL(x86_gsbase_read_cpu_inactive);
>
> void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
> {
> @@ -456,6 +457,7 @@ void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
> wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
> }
> }
> +EXPORT_SYMBOL_GPL(x86_gsbase_write_cpu_inactive);
>
> unsigned long x86_fsbase_read_task(struct task_struct *task)
> {
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 3127c66a1651..48a34d1a2989 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1156,11 +1156,11 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
> } else {
> savesegment(fs, fs_sel);
> savesegment(gs, gs_sel);
> - fs_base = read_msr(MSR_FS_BASE);
> - vmx->msr_host_kernel_gs_base = read_msr(MSR_KERNEL_GS_BASE);
> + fs_base = x86_fsbase_read_cpu();
> + vmx->msr_host_kernel_gs_base = x86_gsbase_read_cpu_inactive();
> }
>
> - wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> + x86_gsbase_write_cpu_inactive(vmx->msr_guest_kernel_gs_base);
> #else
> savesegment(fs, fs_sel);
> savesegment(gs, gs_sel);
> @@ -1184,7 +1184,7 @@ static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx)
> ++vmx->vcpu.stat.host_state_reload;
>
> #ifdef CONFIG_X86_64
> - rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> + vmx->msr_guest_kernel_gs_base = x86_gsbase_read_cpu_inactive();
> #endif
> if (host_state->ldt_sel || (host_state->gs_sel & 7)) {
> kvm_load_ldt(host_state->ldt_sel);
> @@ -1204,7 +1204,7 @@ static void vmx_prepare_switch_to_host(struct vcpu_vmx *vmx)
> #endif
> invalidate_tss_limit();
> #ifdef CONFIG_X86_64
> - wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
> + x86_gsbase_write_cpu_inactive(vmx->msr_host_kernel_gs_base);
> #endif
> load_fixmap_gdt(raw_smp_processor_id());
> vmx->guest_state_loaded = false;
> @@ -1216,7 +1216,7 @@ static u64 vmx_read_guest_kernel_gs_base(struct vcpu_vmx *vmx)
> {
> preempt_disable();
> if (vmx->guest_state_loaded)
> - rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base);
> + vmx->msr_guest_kernel_gs_base = x86_gsbase_read_cpu_inactive();
> preempt_enable();
> return vmx->msr_guest_kernel_gs_base;
> }
> @@ -1225,7 +1225,7 @@ static void vmx_write_guest_kernel_gs_base(struct vcpu_vmx *vmx, u64 data)
> {
> preempt_disable();
> if (vmx->guest_state_loaded)
> - wrmsrl(MSR_KERNEL_GS_BASE, data);
> + x86_gsbase_write_cpu_inactive(data);
> preempt_enable();
> vmx->msr_guest_kernel_gs_base = data;
> }
>