Re: [PATCH v8 05/14] KVM: Allow range-based TLB invalidation from common code

Gavin Shan
2023-08-09T06:10:11Z

On 8/9/23 09:13, Raghavendra Rao Ananta wrote:
> From: David Matlack <dmatlack@google.com>
>
> Make kvm_flush_remote_tlbs_range() visible in common code and create a
> default implementation that just invalidates the whole TLB.
>
> This paves the way for several future features/cleanups:
>
> - Introduction of range-based TLBI on ARM.
> - Eliminating kvm_arch_flush_remote_tlbs_memslot()
> - Moving the KVM/x86 TDP MMU to common code.
>
> No functional change intended.
>
> Signed-off-by: David Matlack <dmatlack@google.com>
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> Reviewed-by: Anup Patel <anup@brainfault.org>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/mmu/mmu.c | 8 ++++----
> arch/x86/kvm/mmu/mmu_internal.h | 3 ---
> include/linux/kvm_host.h | 12 ++++++++++++
> virt/kvm/kvm_main.c | 13 +++++++++++++
> 5 files changed, 31 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index a2d3cfc2eb75c..b547d17c58f63 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1804,6 +1804,8 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
> return -ENOTSUPP;
> }
>
> +#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> +
> #define kvm_arch_pmi_in_guest(vcpu) \
> ((vcpu) && (vcpu)->arch.handling_intr_from_guest)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index ec169f5c7dce2..6adbe6c870982 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -278,16 +278,16 @@ static inline bool kvm_available_flush_remote_tlbs_range(void)
> return kvm_x86_ops.flush_remote_tlbs_range;
> }
>
> -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> - gfn_t nr_pages)
> +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> + u64 nr_pages)
> {
> int ret = -EOPNOTSUPP;
>
> if (kvm_x86_ops.flush_remote_tlbs_range)
> ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, start_gfn,
> nr_pages);
> - if (ret)
> - kvm_flush_remote_tlbs(kvm);
> +
> + return ret;
> }
>

I guess @start_gfn can be renamed to @gfn, to be consistent with its declaration
in include/linux/kvm_host.h and struct kvm_x86_ops::flush_remote_tlbs_range()

> static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index d39af5639ce97..86cb83bb34804 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -170,9 +170,6 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
> struct kvm_memory_slot *slot, u64 gfn,
> int min_level);
>
> -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> - gfn_t nr_pages);
> -
> /* Flush the given page (huge or not) of guest memory. */
> static inline void kvm_flush_remote_tlbs_gfn(struct kvm *kvm, gfn_t gfn, int level)
> {
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ade5d4500c2ce..f0be5d9c37dd1 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1359,6 +1359,7 @@ int kvm_vcpu_yield_to(struct kvm_vcpu *target);
> void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool yield_to_kernel_mode);
>
> void kvm_flush_remote_tlbs(struct kvm *kvm);
> +void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages);
>
> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min);
> @@ -1488,6 +1489,17 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
> int kvm_arch_flush_remote_tlbs(struct kvm *kvm);
> #endif
>
> +#ifndef __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> +static inline int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm,
> + gfn_t gfn, u64 nr_pages)
> +{
> + return -EOPNOTSUPP;
> +}
> +#else
> +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm,
> + gfn_t gfn, u64 nr_pages);
> +#endif
> +
> #ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
> void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
> void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index d6b0507861550..26e91000f579d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -366,6 +366,19 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
> }
> EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
>
> +void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
> +{
> + if (!kvm_arch_flush_remote_tlbs_range(kvm, gfn, nr_pages))
> + return;
> +
> + /*
> + * Fall back to a flushing entire TLBs if the architecture range-based
> + * TLB invalidation is unsupported or can't be performed for whatever
> + * reason.
> + */
> + kvm_flush_remote_tlbs(kvm);
> +}
> +
> static void kvm_flush_shadow_all(struct kvm *kvm)
> {
> kvm_arch_flush_shadow_all(kvm);

Thanks,
Gavin