On Mon, Jan 9, 2023 at 3:41 PM David Matlack [off-list ref] wrote:

On Mon, Jan 09, 2023 at 09:53:44PM +0000, Raghavendra Rao Ananta wrote:

quoted

Define kvm_flush_remote_tlbs_range() to limit the TLB flush only
to a certain range of addresses. Replace this with the existing
call to kvm_flush_remote_tlbs() in the MMU notifier path.
Architectures such as arm64 can define this to flush only the
necessary addresses, instead of the entire range.

Signed-off-by: Raghavendra Rao Ananta <redacted>
---
 arch/arm64/kvm/mmu.c     | 10 ++++++++++
 include/linux/kvm_host.h |  1 +
 virt/kvm/kvm_main.c      |  7 ++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 39d9a334efb57..70f76bc909c5d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c

@@ -91,6 +91,16 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
      kvm_call_hyp(__kvm_tlb_flush_vmid, &kvm->arch.mmu);
 }

+void kvm_flush_remote_tlbs_range(struct kvm *kvm, unsigned long start, unsigned long end)
+{
+     struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
+
+     if (system_supports_tlb_range())
+             kvm_call_hyp(__kvm_tlb_flush_range_vmid_ipa, mmu, start, end, 0);
+     else
+             kvm_flush_remote_tlbs(kvm);
+}
+
 static bool kvm_is_device_pfn(unsigned long pfn)
 {
      return !pfn_is_map_memory(pfn);

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f51eb9419bfc3..a76cede9dc3bb 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 usermode_vcpu_not_eligible);

 void kvm_flush_remote_tlbs(struct kvm *kvm);
+void kvm_flush_remote_tlbs_range(struct kvm *kvm, unsigned long start, unsigned long end);

 #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 03e6a38094c17..f538ecc984f5b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c

@@ -376,6 +376,11 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
              ++kvm->stat.generic.remote_tlb_flush;
 }
 EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
+
+void kvm_flush_remote_tlbs_range(struct kvm *kvm, unsigned long start, unsigned long end)

It's ambiguous what start/end represent. Case in point,
__kvm_handle_hva_range() is passing in HVAs but then patch 4 passes in
GFNs.

Probably kvm_flush_tlbs_range() should accept GFN and there can be a
helper wrapper that does the HVA-to-GFN conversion.

quoted

+{
+     kvm_flush_remote_tlbs(kvm);
+}

You are right, that should've been GFNs, and the function should
operate on GPAs. I can think about a wrapper.

FYI I also proposed a common kvm_flush_remote_tlbs() in my Common MMU
series [1].

Could I interest you in grabbing patches 29-33 from that series, which
has the same end result (common kvm_flush_remote_tlbs_range()) but also
hooks up the KVM/x86 range-based flushing, and folding them into this
series?

Of course! I'll grab them in my next version.

Thank you.
Raghavendra

[1] https://lore.kernel.org/kvm/20221208193857.4090582-33-dmatlack@google.com/ (local)

quoted

 #endif

 static void kvm_flush_shadow_all(struct kvm *kvm)

@@ -637,7 +642,7 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm,
      }

      if (range->flush_on_ret && ret)
-             kvm_flush_remote_tlbs(kvm);
+             kvm_flush_remote_tlbs_range(kvm, range->start, range->end - 1);

      if (locked) {
              KVM_MMU_UNLOCK(kvm);
--

2.39.0.314.g84b9a713c41-goog

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