On 12/04/2018 22:19, KarimAllah Ahmed wrote:
> Update 'tsc_offset' on vmenty/vmexit of L2 guests to ensure that it always
> captures the TSC_OFFSET of the running guest whether it is the L1 or L2
> guest.
>
> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
> ---
> v1 -> v2:
>
> - Rewrote the patch to always update tsc_offset to represent the current
> guest (pbonzini@)
Yes, this is it, thanks. I'll test it tomorrow and if I have time look
at AMD.
Paolo
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/vmx.c | 25 ++++++++++++++++++++-----
> arch/x86/kvm/x86.c | 9 ++++++++-
> 3 files changed, 29 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9fa4f57..3bedfef 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1015,6 +1015,7 @@ struct kvm_x86_ops {
>
> bool (*has_wbinvd_exit)(void);
>
> + u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);
> void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
>
> void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index cff2f50..9e7dd39 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2895,6 +2895,17 @@ static u64 guest_read_tsc(struct kvm_vcpu *vcpu)
> return kvm_scale_tsc(vcpu, host_tsc) + tsc_offset;
> }
>
> +static u64 vmx_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
> +{
> + struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> +
> + if (is_guest_mode(vcpu) &&
> + (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING))
> + return vcpu->arch.tsc_offset - vmcs12->tsc_offset;
> +
> + return vcpu->arch.tsc_offset;
> +}
> +
> /*
> * writes 'offset' into guest's timestamp counter offset register
> */
> @@ -11163,11 +11174,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
> }
>
> - if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
> - vmcs_write64(TSC_OFFSET,
> - vcpu->arch.tsc_offset + vmcs12->tsc_offset);
> - else
> - vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
> + vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
> +
> if (kvm_has_tsc_control)
> decache_tsc_multiplier(vmx);
>
> @@ -11469,6 +11477,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
> if (enable_shadow_vmcs)
> copy_shadow_to_vmcs12(vmx);
>
> + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
> + vcpu->arch.tsc_offset += vmcs12->tsc_offset;
> +
> /*
> * The nested entry process starts with enforcing various prerequisites
> * on vmcs12 as required by the Intel SDM, and act appropriately when
> @@ -12015,6 +12026,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
>
> leave_guest_mode(vcpu);
>
> + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
> + vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
> +
> if (likely(!vmx->fail)) {
> if (exit_reason == -1)
> sync_vmcs12(vcpu, vmcs12);
> @@ -12688,6 +12702,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>
> .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
>
> + .read_l1_tsc_offset = vmx_read_l1_tsc_offset,
> .write_tsc_offset = vmx_write_tsc_offset,
>
> .set_tdp_cr3 = vmx_set_cr3,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ac42c85..3fb1353 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1532,7 +1532,14 @@ static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
>
> u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
> {
> - return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
> + u64 tsc_offset;
> +
> + if (kvm_x86_ops->read_l1_tsc_offset)
> + tsc_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
> + else
> + tsc_offset = vcpu->arch.tsc_offset;
> +
> + return tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
> }
> EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
>
>
