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[RFC,4/7] KVM: arm64: Steply write protect page table by mask bit

Message ID 20200525112406.28224-5-zhukeqian1@huawei.com (mailing list archive)
State New, archived
Headers show
Series kvm: arm64: Support stage2 hardware DBM | expand

Commit Message

zhukeqian May 25, 2020, 11:24 a.m. UTC
During dirty log clear, page table entries are write protected
according to a mask. In the past we write protect all entries
corresponding to the mask from ffs to fls. Though there may be
zero bits between this range, we are holding the kvm mmu lock
so we won't write protect entries that we don't want to.

We are about to add support for hardware management of dirty state
to arm64, holding kvm mmu lock will be not enough. We should write
protect entries steply by mask bit.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
---
 virt/kvm/arm/mmu.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index ff8df9702e04..779859b85d6d 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1568,10 +1568,16 @@  static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
 		gfn_t gfn_offset, unsigned long mask)
 {
 	phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
-	phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
-	phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;
+	phys_addr_t start, end;
+	u32 i;
 
-	stage2_wp_range(kvm, start, end);
+	for (i = __ffs(mask); i <= __fls(mask); i++) {
+		if (test_bit(i, &mask)) {
+			start = (base_gfn + i) << PAGE_SHIFT;
+			end = (base_gfn + i + 1) << PAGE_SHIFT;
+			stage2_wp_range(kvm, start, end);
+		}
+	}
 }
 
 /*