Hi Marc

-----Original Message-----
From: Will Deacon <will@kernel.org>
Sent: Thursday, March 4, 2021 5:13 AM
To: Marc Zyngier <maz@kernel.org>
Cc: Justin He <redacted>; kvmarm@lists.cs.columbia.edu; James
Morse [off-list ref]; Julien Thierry [off-list ref];
Suzuki Poulose [off-list ref]; Catalin Marinas
[off-list ref]; Gavin Shan [off-list ref]; Yanan Wang
[off-list ref]; Quentin Perret [off-list ref]; linux-arm-
kernel@lists.infradead.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: arm64: Fix unaligned addr case in mmu walking

On Wed, Mar 03, 2021 at 07:07:37PM +0000, Marc Zyngier wrote:

quoted

From e0524b41a71e0f17d6dc8f197e421e677d584e72 Mon Sep 17 00:00:00 2001
From: Jia He <redacted>
Date: Wed, 3 Mar 2021 10:42:25 +0800
Subject: [PATCH] KVM: arm64: Fix range alignment when walking page tables

When walking the page tables at a given level, and if the start
address for the range isn't aligned for that level, we propagate
the misalignment on each iteration at that level.

This results in the walker ignoring a number of entries (depending
on the original misalignment) on each subsequent iteration.

Properly aligning the address at the before the next iteration

"at the before the next" ???

quoted

addresses the issue.

Cc: stable@vger.kernel.org
Reported-by: Howard Zhang <redacted>
Signed-off-by: Jia He <redacted>
Fixes: b1e57de62cfb ("KVM: arm64: Add stand-alone page-table walker

infrastructure")

quoted

[maz: rewrite commit message]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210303024225.2591-1-justin.he@arm.com (local)
---
 arch/arm64/kvm/hyp/pgtable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 4d177ce1d536..124cd2f93020 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c

@@ -223,7 +223,7 @@ static inline int __kvm_pgtable_visit(struct

kvm_pgtable_walk_data *data,

quoted

 		goto out;

 	if (!table) {
-		data->addr += kvm_granule_size(level);
+		data->addr = ALIGN(data->addr, kvm_granule_size(level));

What if previous data->addr is already aligned with kvm_granule_size(level)?
Hence a deadloop? Am I missing anything else?

--
Cheers,
Justin (Jia He)

quoted

 		goto out;
 	}

If Jia is happy with it, please feel free to add:

Acked-by: Will Deacon <will@kernel.org>

Will

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