From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1FF04355F46 for ; Tue, 14 Jul 2026 11:03:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784027016; cv=none; b=N8r9WKlYWtQZVRDwAUITYDsxwYuYlepOvVyfU6FHiTiTdccdK4GxZjR9owXV7hBxti+Gnxkym8KqcL9duWvBs/2BFhkqBm9gdKIOawSmOUta/n4mwuZd42DS41Mr3bEgt8g9yz6wZhWQv2OpeUtXKEGChSdarPqCJ7r2tfl9wUM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784027016; c=relaxed/simple; bh=1wVk/tQdaNhnArh4J0BQVcadplivbnaPbQao/4sAzu4=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=E3Kpn8Q6KKUmp6ecoeVa4UihfWngUxouRTzBmNB5YDxQFuesEPBEVpSyKgl/aw/7YSiEzdIn6F+kByA2v7XaR+MPdXJlP1TAtMxT3d/nRKW1tkRnDFUSlleeRHH/FNvWQhltQLx55eYFlh0nod2Ei/aWXQjNV2Ta56/lq5A56/A= 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=jRkIAqW9; arc=none smtp.client-ip=91.218.175.188 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="jRkIAqW9" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784027012; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=UgPclGQHh7dNphdFO4WD5DMAk53aRk6exDDyQp10qx4=; b=jRkIAqW9xU+yEp9z4uZF+l5JWILsxZz9syYK8tKVl79qvKNeLhZnNVCyA6GqSadTYJoNBY 9TfJZ1IbkiZKBAjqCeT4jdA9dqfQRKJUorY6APff0Nk6D9t1dkpm1LKu3TjecHeHraA0qo 5l8XdhA+ThUr25wNqP0bpDaGfOWw7os= From: Fuad Tabba To: kvm@vger.kernel.org Cc: kvmarm@lists.linux.dev, Will Deacon , Julien Thierry , Alexandru Elisei , Suzuki K Poulose , Andre Przywara , Oliver Upton , Marc Zyngier , Fuad Tabba Subject: [PATCH] arm64: Query per-VM capabilities when selecting vCPU features Date: Tue, 14 Jul 2026 12:03:29 +0100 Message-Id: <20260714110329.12113-1-fuad.tabba@linux.dev> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT kvm_cpu__select_features() and kvm_cpu__configure_features() probe vCPU feature availability with kvm__supports_extension(), which issues KVM_CHECK_EXTENSION on the global /dev/kvm fd. That reports the host's raw capabilities, unaware of any per-VM restrictions. Protected VMs support a subset of the host's features. The kernel reflects this on the VM fd (commit a3163dca4817 ("KVM: arm64: Use KVM extension checks for allowed protected VM capabilities")), while the global fd still advertises capabilities such as SVE that the VM cannot use. kvmtool then requests SVE in KVM_ARM_VCPU_INIT, which the kernel rejects. Query these capabilities on the VM fd via kvm__supports_vm_extension(). More generally, vCPU feature availability is a per-VM property and is better checked against the VM fd than the global one. Signed-off-by: Fuad Tabba --- arm64/kvm-cpu.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arm64/kvm-cpu.c b/arm64/kvm-cpu.c index ae5a6eb..3aa7684 100644 --- a/arm64/kvm-cpu.c +++ b/arm64/kvm-cpu.c @@ -53,34 +53,34 @@ int kvm_cpu__register_kvm_arm_target(struct kvm_arm_target *target) static void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init *init) { if (kvm->cfg.arch.aarch32_guest) { - if (!kvm__supports_extension(kvm, KVM_CAP_ARM_EL1_32BIT)) + if (!kvm__supports_vm_extension(kvm, KVM_CAP_ARM_EL1_32BIT)) die("32bit guests are not supported\n"); init->features[0] |= 1UL << KVM_ARM_VCPU_EL1_32BIT; } if (kvm->cfg.arch.has_pmuv3) { - if (!kvm__supports_extension(kvm, KVM_CAP_ARM_PMU_V3)) + if (!kvm__supports_vm_extension(kvm, KVM_CAP_ARM_PMU_V3)) die("PMUv3 is not supported"); init->features[0] |= 1UL << KVM_ARM_VCPU_PMU_V3; } /* Enable pointer authentication if available */ - if (kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_ADDRESS) && - kvm__supports_extension(kvm, KVM_CAP_ARM_PTRAUTH_GENERIC)) { + if (kvm__supports_vm_extension(kvm, KVM_CAP_ARM_PTRAUTH_ADDRESS) && + kvm__supports_vm_extension(kvm, KVM_CAP_ARM_PTRAUTH_GENERIC)) { init->features[0] |= 1UL << KVM_ARM_VCPU_PTRAUTH_ADDRESS; init->features[0] |= 1UL << KVM_ARM_VCPU_PTRAUTH_GENERIC; } /* Enable SVE if available */ - if (kvm__supports_extension(kvm, KVM_CAP_ARM_SVE)) + if (kvm__supports_vm_extension(kvm, KVM_CAP_ARM_SVE)) init->features[0] |= 1UL << KVM_ARM_VCPU_SVE; if (kvm->cfg.arch.nested_virt) { - if (!kvm__supports_extension(kvm, KVM_CAP_ARM_EL2)) + if (!kvm__supports_vm_extension(kvm, KVM_CAP_ARM_EL2)) die("EL2 (nested virt) is not supported"); init->features[0] |= 1UL << KVM_ARM_VCPU_HAS_EL2; if (kvm->cfg.arch.e2h0) { - if (!kvm__supports_extension(kvm, KVM_CAP_ARM_EL2_E2H0)) + if (!kvm__supports_vm_extension(kvm, KVM_CAP_ARM_EL2_E2H0)) die("FEAT_E2H0 is not supported"); init->features[0] |= 1UL << KVM_ARM_VCPU_HAS_EL2_E2H0; } @@ -123,7 +123,7 @@ static int vcpu_configure_sve(struct kvm_cpu *vcpu) static int kvm_cpu__configure_features(struct kvm_cpu *vcpu) { - if (kvm__supports_extension(vcpu->kvm, KVM_CAP_ARM_SVE)) + if (kvm__supports_vm_extension(vcpu->kvm, KVM_CAP_ARM_SVE)) return vcpu_configure_sve(vcpu); return 0; -- 2.39.5