diff mbox series

[v9,05/14] KVM: Allow range-based TLB invalidation from common code

Message ID 20230811045127.3308641-6-rananta@google.com (mailing list archive)
State New, archived
Headers show
Series KVM: arm64: Add support for FEAT_TLBIRANGE | expand

Commit Message

Raghavendra Rao Ananta Aug. 11, 2023, 4:51 a.m. UTC 
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          | 10 ++++------
 arch/x86/kvm/mmu/mmu_internal.h |  3 ---
 include/linux/kvm_host.h        | 11 +++++++++++
 virt/kvm/kvm_main.c             | 13 +++++++++++++
 5 files changed, 30 insertions(+), 9 deletions(-)

Comments

Sean Christopherson Aug. 15, 2023, 10:30 p.m. UTC | #1 
On Fri, Aug 11, 2023, Raghavendra Rao Ananta wrote:
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index ec169f5c7dce2..00f7bda9202f2 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -278,16 +278,14 @@ 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 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);
> +		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> +
> +	return ret;

Please write this as

	if (kvm_x86_ops.flush_remote_tlbs_range)
		return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);

	return -EOPNOTSUPP;

or alternatively

	if (!kvm_x86_ops.flush_remote_tlbs_range)
		return -EOPNOTSUPP;

	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);

Hmm, I'll throw my official vote for the second version.

The local "ret" is unnecessary and is suprisingly dangerous.  I screwed up the
conflict resolution when cherry-picking my CONFIG_HYPERV change to see what the
conflict looked like and ended up with a double flush:

	int ret = -EOPNOTSUPP;

	if (kvm_x86_ops.flush_remote_tlbs_range)
		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);

	if (ret)
		kvm_flush_remote_tlbs(kvm);

	return ret;

Dropping "ret" makes it much harder to get trigger happy when resolving conflicts.

No need for a new version to fix the above, assuming Marc/Oliver is ok doing
fixup when applying.

Nit aside, looks good for x86, and I know of no conflicts, so take 'er away!

Acked-by: Sean Christopherson <seanjc@google.com>
Marc Zyngier Aug. 17, 2023, 8:39 a.m. UTC | #2 
On Tue, 15 Aug 2023 23:30:08 +0100,
Sean Christopherson <seanjc@google.com> wrote:
> 
> On Fri, Aug 11, 2023, Raghavendra Rao Ananta wrote:
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index ec169f5c7dce2..00f7bda9202f2 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -278,16 +278,14 @@ 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 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);
> > +		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> > +
> > +	return ret;
> 
> Please write this as
> 
> 	if (kvm_x86_ops.flush_remote_tlbs_range)
> 		return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> 
> 	return -EOPNOTSUPP;
> 
> or alternatively
> 
> 	if (!kvm_x86_ops.flush_remote_tlbs_range)
> 		return -EOPNOTSUPP;
> 
> 	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> 
> Hmm, I'll throw my official vote for the second version.

I've applied the second version locally.

	M.
diff mbox series

Patch

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..00f7bda9202f2 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -278,16 +278,14 @@  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 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);
+		ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
+
+	return ret;
 }
 
 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..89d2614e4b7a6 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 +1489,16 @@  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);