Subject: [PATCH 7/7] KVM: arm/arm64: Elide CMOs when unmapping a range

From: Marc Zyngier <[email-masked]>
Date: Fri, 13 Dec 2019 18:25:03 +0000

If userspace issues a munmap() on a set of pages, there is no
expectation that the pages are cleaned to the PoC. So let's
not do more work than strictly necessary, and set the magic
flag that avoids CMOs in this case.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 virt/kvm/arm/mmu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index c55022dbac89..6749be33d822 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -2056,7 +2056,13 @@ static int handle_hva_to_gpa(struct kvm *kvm,
 
 static int kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data)
 {
-	unmap_stage2_range(kvm, gpa, size, 0);
+	struct mmu_notifier_range *range = data;
+	unsigned long flags = 0;
+
+	if (range->event == MMU_NOTIFY_UNMAP)
+		flags = KVM_UNMAP_ELIDE_CMO;
+
+	unmap_stage2_range(kvm, gpa, size, flags);
 	return 0;
 }
 
@@ -2067,7 +2073,7 @@ int kvm_unmap_hva_range(struct kvm *kvm, const struct mmu_notifier_range *range)
 
 	trace_kvm_unmap_hva_range(range->start, range->end);
 	handle_hva_to_gpa(kvm, range->start, range->end,
-			  &kvm_unmap_hva_handler, NULL);
+			  &kvm_unmap_hva_handler, (void *)range);
 	return 0;
 }
 
-- 
2.20.1

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