linux-kernel - [PATCH 1/2] KVM: arm64: Improve error handling from check_host_shared

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Message-ID: <20250207145438.1333475-2-qperret@google.com>
Date: Fri,  7 Feb 2025 14:54:37 +0000
From: Quentin Perret <qperret@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
	Zenghui Yu <yuzenghui@...wei.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>
Cc: Fuad Tabba <tabba@...gle.com>, Vincent Donnefort <vdonnefort@...gle.com>, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] KVM: arm64: Improve error handling from check_host_shared_guest()

The check_host_shared_guest() path expects to find a last-level valid
PTE in the guest's stage-2 page-table. However, it checks the PTE's
level before its validity, which makes it hard for callers to figure out
what went wrong.

To make error handling simpler, check the PTE's validity first.

Signed-off-by: Quentin Perret <qperret@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 7ad7b133b81a..41847c04b270 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -943,10 +943,10 @@ static int __check_host_shared_guest(struct pkvm_hyp_vm *vm, u64 *__phys, u64 ip
 	ret = kvm_pgtable_get_leaf(&vm->pgt, ipa, &pte, &level);
 	if (ret)
 		return ret;
-	if (level != KVM_PGTABLE_LAST_LEVEL)
-		return -E2BIG;
 	if (!kvm_pte_valid(pte))
 		return -ENOENT;
+	if (level != KVM_PGTABLE_LAST_LEVEL)
+		return -E2BIG;
 
 	state = guest_get_page_state(pte, ipa);
 	if (state != PKVM_PAGE_SHARED_BORROWED)
-- 
2.48.1.502.g6dc24dfdaf-goog