On Fri, Feb 25, 2022 at 10:22 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Remove the generic kvm_reload_remote_mmus() and open code its
> functionality into the two x86 callers. x86 is (obviously) the only
> architecture that uses the hook, and is also the only architecture that
> uses KVM_REQ_MMU_RELOAD in a way that's consistent with the name. That
> will change in a future patch, as x86's usage when zapping a single
> shadow page x86 doesn't actually _need_ to reload all vCPUs' MMUs, only
> MMUs whose root is being zapped actually need to be reloaded.
>
> s390 also uses KVM_REQ_MMU_RELOAD, but for a slightly different purpose.
>
> Drop the generic code in anticipation of implementing s390 and x86 arch
> specific requests, which will allow dropping KVM_REQ_MMU_RELOAD entirely.
>
> Opportunistically reword the x86 TDP MMU comment to avoid making
> references to functions (and requests!) when possible, and to remove the
> rather ambiguous "this".
>
> No functional change intended.
>
> Cc: Ben Gardon <bgardon@xxxxxxxxxx>
Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 14 +++++++-------
> include/linux/kvm_host.h | 1 -
> virt/kvm/kvm_main.c | 5 -----
> 3 files changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b2c1c4eb6007..32c6d4b33d03 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2353,7 +2353,7 @@ static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm,
> * treats invalid shadow pages as being obsolete.
> */
> if (!is_obsolete_sp(kvm, sp))
> - kvm_reload_remote_mmus(kvm);
> + kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
> }
>
> if (sp->lpage_disallowed)
> @@ -5639,11 +5639,11 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
> */
> kvm->arch.mmu_valid_gen = kvm->arch.mmu_valid_gen ? 0 : 1;
>
> - /* In order to ensure all threads see this change when
> - * handling the MMU reload signal, this must happen in the
> - * same critical section as kvm_reload_remote_mmus, and
> - * before kvm_zap_obsolete_pages as kvm_zap_obsolete_pages
> - * could drop the MMU lock and yield.
> + /*
> + * In order to ensure all vCPUs drop their soon-to-be invalid roots,
> + * invalidating TDP MMU roots must be done while holding mmu_lock for
> + * write and in the same critical section as making the reload request,
> + * e.g. before kvm_zap_obsolete_pages() could drop mmu_lock and yield.
> */
> if (is_tdp_mmu_enabled(kvm))
> kvm_tdp_mmu_invalidate_all_roots(kvm);
> @@ -5656,7 +5656,7 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
> * Note: we need to do this under the protection of mmu_lock,
> * otherwise, vcpu would purge shadow page but miss tlb flush.
> */
> - kvm_reload_remote_mmus(kvm);
> + kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
>
> kvm_zap_obsolete_pages(kvm);
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index f11039944c08..0aeb47cffd43 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1325,7 +1325,6 @@ int kvm_vcpu_yield_to(struct kvm_vcpu *target);
> void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
>
> void kvm_flush_remote_tlbs(struct kvm *kvm);
> -void kvm_reload_remote_mmus(struct kvm *kvm);
>
> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 83c57bcc6eb6..66bb1631cb89 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -354,11 +354,6 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
> EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
> #endif
>
> -void kvm_reload_remote_mmus(struct kvm *kvm)
> -{
> - kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_RELOAD);
> -}
> -
> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
> gfp_t gfp_flags)
> --
> 2.35.1.574.g5d30c73bfb-goog
>
