On Sun, Oct 11, 2020 at 02:48:17PM -0400, Cathy Avery wrote:
> Move asid to svm->asid to allow for vmcb assignment
This is misleading. The asid isn't being moved, it's being copied/tracked.
The "to allow" wording also confused me; I though this was just a prep patch
and the actual assignment was in a follow-up patch.
> during svm_vcpu_run without regard to which level
> guest is running.
> Signed-off-by: Cathy Avery <cav...@redhat.com>
> ---
> arch/x86/kvm/svm/svm.c | 4 +++-
> arch/x86/kvm/svm/svm.h | 1 +
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index d4e18bda19c7..619980a5d540 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1101,6 +1101,7 @@ static void init_vmcb(struct vcpu_svm *svm)
> save->cr4 = 0;
> }
> svm->asid_generation = 0;
> + svm->asid = 0;
>
> svm->nested.vmcb = 0;
> svm->vcpu.arch.hflags = 0;
> @@ -1663,7 +1664,7 @@ static void new_asid(struct vcpu_svm *svm, struct
> svm_cpu_data *sd)
> }
>
> svm->asid_generation = sd->asid_generation;
> - svm->vmcb->control.asid = sd->next_asid++;
> + svm->asid = sd->next_asid++;
> vmcb_mark_dirty(svm->vmcb, VMCB_ASID);
I know very little (ok, nothing) about SVM VMCB caching rules, but I strongly
suspect this is broken. The existing code explicitly marks VMCB_ASID dirty,
but there is no equivalent code for the case where there are multiple VMCBs,
e.g. if new_asid() is called while vmcb01 is active, then vmcb02 will pick up
the new ASID but will not mark it dirty.
> }
> @@ -3446,6 +3447,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct
> kvm_vcpu *vcpu)
>
> sync_lapic_to_cr8(vcpu);
>
> + svm->vmcb->control.asid = svm->asid;
Related to the above, handling this in vcpu_run() feels wrong. There really
shouldn't be a need to track the ASID. vmcb01 will always exist if vmcb02
exits, e.g. the ASID can be copied and marked dirty when loading vmcb02.
For new_asid(), it can unconditionally update vmcb01 and conditionally update
vmcb02.
> svm->vmcb->save.cr2 = vcpu->arch.cr2;
>
> /*
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index a798e1731709..862f0d2405e8 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -104,6 +104,7 @@ struct vcpu_svm {
> struct vmcb *vmcb;
> unsigned long vmcb_pa;
> struct svm_cpu_data *svm_data;
> + u32 asid;
> uint64_t asid_generation;
> uint64_t sysenter_esp;
> uint64_t sysenter_eip;
> --
> 2.20.1
>
