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[v3,1/3] RISC-V: KVM: Fix lost write protection on huge pages during dirty logging

Message ID 20260316141631543e3oVI3JGADhz5veSRD_eC@zte.com.cn
State Changes Requested
Headers show
Series RISC-V: KVM: Fix hugepage mapping handling during dirty logging | expand

Commit Message

wang.yechao255@zte.com.cn March 16, 2026, 6:16 a.m. UTC 
From: Wang Yechao <wang.yechao255@zte.com.cn>

When enabling dirty log in small chunks (e.g., QEMU default chunk
size of 256K), the chunk size is always smaller than the page size
of huge pages (1G or 2M) used in the gstage page tables. This caused
the write protection to be incorrectly skipped for huge PTEs because
the condition `(end - addr) >= page_size` was not satisfied.

Remove the size check in `kvm_riscv_gstage_wp_range()` to ensure huge
PTEs are always write-protected regardless of the chunk size. Additionally,
explicitly align the address down to the page size before invoking
`kvm_riscv_gstage_op_pte()` to guarantee that the address passed to the
operation function is page-aligned.

This fixes the issue where dirty pages might not be tracked correctly
when using huge pages.

Fixes: 9d05c1fee837 ("RISC-V: KVM: Implement stage2 page table programming")
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
---
 arch/riscv/kvm/gstage.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Comments

Anup Patel March 30, 2026, 6:25 a.m. UTC | #1 
On Mon, Mar 16, 2026 at 11:46 AM <wang.yechao255@zte.com.cn> wrote:
>
> From: Wang Yechao <wang.yechao255@zte.com.cn>
>
> When enabling dirty log in small chunks (e.g., QEMU default chunk
> size of 256K), the chunk size is always smaller than the page size
> of huge pages (1G or 2M) used in the gstage page tables. This caused
> the write protection to be incorrectly skipped for huge PTEs because
> the condition `(end - addr) >= page_size` was not satisfied.
>
> Remove the size check in `kvm_riscv_gstage_wp_range()` to ensure huge
> PTEs are always write-protected regardless of the chunk size. Additionally,
> explicitly align the address down to the page size before invoking
> `kvm_riscv_gstage_op_pte()` to guarantee that the address passed to the
> operation function is page-aligned.
>
> This fixes the issue where dirty pages might not be tracked correctly
> when using huge pages.
>
> Fixes: 9d05c1fee837 ("RISC-V: KVM: Implement stage2 page table programming")
> Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
> Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup


> ---
>  arch/riscv/kvm/gstage.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
> index b67d60d722c2..d2001d508046 100644
> --- a/arch/riscv/kvm/gstage.c
> +++ b/arch/riscv/kvm/gstage.c
> @@ -304,10 +304,9 @@ void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
>                 if (!found_leaf)
>                         goto next;
>
> -               if (!(addr & (page_size - 1)) && ((end - addr) >= page_size))
> -                       kvm_riscv_gstage_op_pte(gstage, addr, ptep,
> -                                               ptep_level, GSTAGE_OP_WP);
> -
> +               addr = ALIGN_DOWN(addr, page_size);
> +               kvm_riscv_gstage_op_pte(gstage, addr, ptep,
> +                                       ptep_level, GSTAGE_OP_WP);
>  next:
>                 addr += page_size;
>         }
> --
> 2.27.0
diff mbox series

Patch

diff --git a/arch/riscv/kvm/gstage.c b/arch/riscv/kvm/gstage.c
index b67d60d722c2..d2001d508046 100644
--- a/arch/riscv/kvm/gstage.c
+++ b/arch/riscv/kvm/gstage.c
@@ -304,10 +304,9 @@  void kvm_riscv_gstage_wp_range(struct kvm_gstage *gstage, gpa_t start, gpa_t end
 		if (!found_leaf)
 			goto next;

-		if (!(addr & (page_size - 1)) && ((end - addr) >= page_size))
-			kvm_riscv_gstage_op_pte(gstage, addr, ptep,
-						ptep_level, GSTAGE_OP_WP);
-
+		addr = ALIGN_DOWN(addr, page_size);
+		kvm_riscv_gstage_op_pte(gstage, addr, ptep,
+					ptep_level, GSTAGE_OP_WP);
 next:
 		addr += page_size;
 	}