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Mon, 10 Nov 2025 05:45:28 -0800 (PST) Date: Mon, 10 Nov 2025 13:45:19 +0000 In-Reply-To: <20251110134525.3768197-1-tabba@google.com> Mime-Version: 1.0 References: <20251110134525.3768197-1-tabba@google.com> X-Mailer: git-send-email 2.51.2.1041.gc1ab5b90ca-goog Message-ID: <20251110134525.3768197-3-tabba@google.com> Subject: [PATCH v3 2/8] KVM: arm64: Fix Trace Buffer trap polarity for protected VMs From: Fuad Tabba To: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: maz@kernel.org, oliver.upton@linux.dev, will@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, vladimir.murzin@arm.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251110_054531_080467_F1DEDD7F X-CRM114-Status: GOOD ( 13.17 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The E2TB bits in MDCR_EL2 control trapping of Trace Buffer system register accesses. These accesses are trapped to EL2 when the bits are clear. The trap initialization logic for protected VMs in pvm_init_traps_mdcr() had the polarity inverted. When a guest did not support the Trace Buffer feature, the code was setting E2TB. This incorrectly disabled the trap, potentially allowing a protected guest to access registers for a feature it was not given. Fix this by inverting the operation. Fixes: f50758260bff ("KVM: arm64: Group setting traps for protected VMs by control register") Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/nvhe/pkvm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 8d06a246dfd1..f6f8996c4f97 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -118,7 +118,7 @@ static void pvm_init_traps_mdcr(struct kvm_vcpu *vcpu) val |= MDCR_EL2_TTRF; if (!kvm_has_feat(kvm, ID_AA64DFR0_EL1, TraceBuffer, IMP)) - val |= MDCR_EL2_E2TB_MASK; + val &= ~MDCR_EL2_E2TB_MASK; /* Trap Debug Communications Channel registers */ if (!kvm_has_feat(kvm, ID_AA64MMFR0_EL1, FGT, IMP)) -- 2.51.2.1041.gc1ab5b90ca-goog