Re: [PATCH] arm64: KVM: fix VTTBR_BADDR_MASK BUG_ON off-by-one
On Tue, Nov 14, 2017 at 02:37:43PM +, Kristina Martsenko wrote:
> VTTBR_BADDR_MASK is used to sanity check the size and alignment of the
> VTTBR address. It seems to currently be off by one, thereby only
> allowing up to 47-bit addresses (instead of 48-bit) and also
> insufficiently checking the alignment. This patch fixes it.
>
> As an example, with 4k pages, before this patch we have:
>
> PHYS_MASK_SHIFT = 48
> VTTBR_X = 37 - 24 = 13
> VTTBR_BADDR_SHIFT = 13 - 1 = 12
> VTTBR_BADDR_MASK = ((1 << 35) - 1) << 12 = 0x7000
>
> Which is wrong, because the mask doesn't allow bit 47 of the VTTBR
> address to be set, and only requires the address to be 12-bit (4k)
> aligned, while it actually needs to be 13-bit (8k) aligned because we
> concatenate two 4k tables.
>
> With this patch, the mask becomes 0xe000, which is what we
> want.
>
> Fixes: 0369f6a34b9f ("arm64: KVM: EL2 register definitions")
> Cc: # 3.11.x
> Reviewed-by: Suzuki K Poulose
> Signed-off-by: Kristina Martsenko
> ---
> arch/arm64/include/asm/kvm_arm.h | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h
> b/arch/arm64/include/asm/kvm_arm.h
> index 61d694c2eae5..555d463c0eaa 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -170,8 +170,7 @@
> #define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS |
> VTCR_EL2_TGRAN_FLAGS)
> #define VTTBR_X (VTTBR_X_TGRAN_MAGIC -
> VTCR_EL2_T0SZ_IPA)
>
> -#define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
> -#define VTTBR_BADDR_MASK (((UL(1) << (PHYS_MASK_SHIFT - VTTBR_X)) - 1) <<
> VTTBR_BADDR_SHIFT)
> +#define VTTBR_BADDR_MASK (((UL(1) << (PHYS_MASK_SHIFT - VTTBR_X)) - 1) <<
> VTTBR_X)
> #define VTTBR_VMID_SHIFT (UL(48))
> #define VTTBR_VMID_MASK(size) (_AT(u64, (1 << size) - 1) << VTTBR_VMID_SHIFT)
>
> --
> 2.1.4
>
Reviewed-by: Christoffer Dall
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[PATCH] arm64: KVM: fix VTTBR_BADDR_MASK BUG_ON off-by-one
VTTBR_BADDR_MASK is used to sanity check the size and alignment of the
VTTBR address. It seems to currently be off by one, thereby only
allowing up to 47-bit addresses (instead of 48-bit) and also
insufficiently checking the alignment. This patch fixes it.
As an example, with 4k pages, before this patch we have:
PHYS_MASK_SHIFT = 48
VTTBR_X = 37 - 24 = 13
VTTBR_BADDR_SHIFT = 13 - 1 = 12
VTTBR_BADDR_MASK = ((1 << 35) - 1) << 12 = 0x7000
Which is wrong, because the mask doesn't allow bit 47 of the VTTBR
address to be set, and only requires the address to be 12-bit (4k)
aligned, while it actually needs to be 13-bit (8k) aligned because we
concatenate two 4k tables.
With this patch, the mask becomes 0xe000, which is what we
want.
Fixes: 0369f6a34b9f ("arm64: KVM: EL2 register definitions")
Cc: # 3.11.x
Reviewed-by: Suzuki K Poulose
Signed-off-by: Kristina Martsenko
---
arch/arm64/include/asm/kvm_arm.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 61d694c2eae5..555d463c0eaa 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -170,8 +170,7 @@
#define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS |
VTCR_EL2_TGRAN_FLAGS)
#define VTTBR_X(VTTBR_X_TGRAN_MAGIC -
VTCR_EL2_T0SZ_IPA)
-#define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
-#define VTTBR_BADDR_MASK (((UL(1) << (PHYS_MASK_SHIFT - VTTBR_X)) - 1) <<
VTTBR_BADDR_SHIFT)
+#define VTTBR_BADDR_MASK (((UL(1) << (PHYS_MASK_SHIFT - VTTBR_X)) - 1) <<
VTTBR_X)
#define VTTBR_VMID_SHIFT (UL(48))
#define VTTBR_VMID_MASK(size) (_AT(u64, (1 << size) - 1) << VTTBR_VMID_SHIFT)
--
2.1.4
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