[PATCH 16/16] KVM: arm64: pkvm: Unshare guest structs during teardown
Marc Zyngier
maz at kernel.org
Mon Oct 18 10:12:22 PDT 2021
On 2021-10-18 15:03, Quentin Perret wrote:
> On Monday 18 Oct 2021 at 11:32:13 (+0100), Quentin Perret wrote:
>> Another option is to take a refcount on 'current' from
>> kvm_arch_vcpu_run_map_fp() before sharing thread-specific structs with
>> the hyp and release the refcount of the previous task after unsharing.
>> But that means we'll have to also drop the refcount when the vcpu
>> gets destroyed, as well as explicitly unshare at that point. Shouldn't
>> be too bad I think. Thoughts?
>
> Something like the below seems to work OK on my setup, including
> SIGKILL'ing the guest and such. How much do you hate it?
It is annoyingly elegant! Small nitpick below.
>
> diff --git a/arch/arm64/include/asm/kvm_host.h
> b/arch/arm64/include/asm/kvm_host.h
> index f8be56d5342b..50598d704c71 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -322,6 +322,7 @@ struct kvm_vcpu_arch {
>
> struct thread_info *host_thread_info; /* hyp VA */
> struct user_fpsimd_state *host_fpsimd_state; /* hyp VA */
> + struct task_struct *parent_task;
>
> struct {
> /* {Break,watch}point registers */
> @@ -738,6 +739,7 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu
> *vcpu);
> void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
> +void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu);
>
> static inline bool kvm_pmu_counter_deferred(struct perf_event_attr
> *attr)
> {
> diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
> index 2fe1128d9f3d..27afeebbe1cb 100644
> --- a/arch/arm64/kvm/fpsimd.c
> +++ b/arch/arm64/kvm/fpsimd.c
> @@ -15,6 +15,22 @@
> #include <asm/kvm_mmu.h>
> #include <asm/sysreg.h>
>
> +void kvm_vcpu_unshare_task_fp(struct kvm_vcpu *vcpu)
> +{
> + struct task_struct *p = vcpu->arch.parent_task;
> + struct user_fpsimd_state *fpsimd;
> + struct thread_info *ti;
> +
> + if (!static_branch_likely(&kvm_protected_mode_initialized) || !p)
Shouldn't this be a check on is_protected_kvm_enabled() instead?
The two should be equivalent outside of the initialisation code...
Otherwise, ship it.
M.
--
Jazz is not dead. It just smells funny...
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