From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-128.mta0.migadu.com [91.218.175.128]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D37D444BCB5 for ; Tue, 15 Sep 2026 07:04:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.128 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789455868; cv=none; b=XKcjyXB7ALqtc3ME5pF5Q1k5D9RsPwu/dfSKKNRwiHpwUjwI1shl0pI5HXKjb7smNGGvpXpwq2GSAm+kKxJDCGkQJG+rLB2a/+zxB+RheTEDda9IyKItjpHmkJVZKu81XzMH7WsdpGDHfcOiUHIxWITNuXKufwvBHMYV7jdkqF8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789455868; c=relaxed/simple; bh=TxjB2nuw/omS0r1HuiWJ8ceXglPNuUd+88Xw3+fRY0o=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=cbJmdM/OM6P92/IVlI00G2SRhPInazwCxGY4dNPkj+bQDVrI/TpdyEAV6C4eeDRU1EutzXGY2vE0y2rKdEWnlQkcSGZHGzfoWhCdg1XobECozrTbb5APYTC03eQ6C8mpf0x9z1RURWJVX38f6+bQRD1obiO2QRPAYM4Tt+toeO4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=RfYBmcS7; arc=none smtp.client-ip=91.218.175.128 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="RfYBmcS7" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=TxjB2nuw/omS0r1HuiWJ8ceXglPNuUd+88Xw3+fRY0o=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789455864; v=1; x=1790060664; b=RfYBmcS79BbKA5YbpkzRHGNMsCdzXRD1HEpL6hdNfl/pGiDHfUrufUgaKXXUPH/IHYRiBT23 Iwz3Kn12AcPNbXgE1yV2U/XRabVttCjM3d7gNYu+FqlFKxra+ZQ9ca17ZnyJup/oUvuH3mDdPBQ Ode+nbxhx5VGh0EOwRXLWuoA= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id d9900a21abb41ef0; Tue, 15 Sep 2026 07:04:24 +0000 X-Mizu-Trace-ID: d9900a21abb41ef0 X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, mark.rutland@arm.com, steven.price@arm.com, vdonnefort@google.com, qperret@google.com, tabba@google.com Subject: [PATCH v2 2/2] KVM: arm64: Pin the host vCPU before adjusting its PC under pKVM Date: Tue, 15 Sep 2026 08:04:18 +0100 Message-Id: <20260915070418.3209779-3-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260915070418.3209779-1-fuad.tabba@linux.dev> References: <20260915070418.3209779-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Under pKVM, a page the host shares with EL2 is mapped at EL2 only while it's pinned, and the host vCPU is pinned at its first KVM_RUN. KVM_SET_VCPU_EVENTS with ext_dabt_pending reaches __kvm_adjust_pc() at EL2 before that, and dereferencing the unmapped host vCPU panics the hypervisor. Any process holding /dev/kvm on a pKVM host can trigger it. Pin the host vCPU around the adjustment when no hyp vCPU is loaded for it. A loaded hyp vCPU implies it's pinned. A pin fails only for memory the host never shared, and the request is then dropped like any other bad host pointer. Fixes: efa1368ba9f4b ("KVM: arm64: Commit exceptions from KVM_SET_VCPU_EVENTS immediately") Cc: stable@vger.kernel.org Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 9a3b92e626adb..4cb7347db2514 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -542,8 +542,25 @@ static void handle___pkvm_host_mkyoung_guest(struct kvm_cpu_context *host_ctxt) static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt) { DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1); + struct pkvm_hyp_vcpu *hyp_vcpu; + struct kvm_vcpu *host_vcpu; - __kvm_adjust_pc(kern_hyp_va(vcpu)); + host_vcpu = __get_host_hyp_vcpus(vcpu, &hyp_vcpu); + if (host_vcpu) { + __kvm_adjust_pc(host_vcpu); + return; + } + + /* + * With no hyp vCPU loaded for it, the host vCPU may be unpinned, + * and so unmapped at EL2: its first run pins it. + */ + host_vcpu = kern_hyp_va(vcpu); + if (hyp_pin_shared_mem(host_vcpu, host_vcpu + 1)) + return; + + __kvm_adjust_pc(host_vcpu); + hyp_unpin_shared_mem(host_vcpu, host_vcpu + 1); } static void handle___kvm_flush_vm_context(struct kvm_cpu_context *host_ctxt) -- 2.39.5