From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 28EB32652B0; Sun, 1 Mar 2026 01:19:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772327976; cv=none; b=ngNozr85v8Ca8dNdLoN1r4oviXy44ow5ywp4sBBrfHAGLHfwRwsFEYC0BJgZEcF9So17jjWj+UE9N/zx4ELpQ3A5Rusu9//OmawzEuJCsUwt7rOMDE3UpSnuVaCTuTHcpEES/2sntRrytHNxVc8v2ANWz1szoGYhxe6TEqo5GYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772327976; c=relaxed/simple; bh=5Se/J/Q85ATeMzpKU7MLPxkcuheMXVH9bPe3fl3XHlQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=IyCj9KBnn/NNBM74dv2t7XNx5OoljVJR9NiBd5el3Rw6/YLPdDF7OEOm1jY5lMAgphMD1GmiT+NtRx6PrhPBfwb1bdp2ZCCLLnA9mnc7ehFeK3vZ9k4BTftamuK1ATI3gAOGxPgWmL5fgtJl1Imzq7DNjjkt/zp4wrtCmGVrKIM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VZQGONlx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VZQGONlx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C4F2C19421; Sun, 1 Mar 2026 01:19:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772327976; bh=5Se/J/Q85ATeMzpKU7MLPxkcuheMXVH9bPe3fl3XHlQ=; h=From:To:Cc:Subject:Date:From; b=VZQGONlxlQHkZbOz+P6wWkHs4oFjl2YpOvzdndZ9BFYIv0Q8KfLC7wnanUoc81Y3c 9iIFdr1yGrO3T4zLSWJGW2gdxlUa2oqmiBYkP2P+fEI/myvD+XhjM2AQKWZ44CIIQN b69hvDGGgqwm5ePwg7Ji8dD9z/F9kpH8Zow8xSX5PQGmaExRE5UM94y1aCsghrOYeD E5NEl/Okw2/FbofR9+RlKAsq4L1saydxDS5c2j2rAvkQ7buLoFyZLmiqhQB+qous3c pMv1LkPySdtwkQz92pgPQ6tug5TN71XBCrWDRAsw4XVKokyQHt5pk3/kRGkJ6n/hCR WOjgyJa/BdERw== From: Sasha Levin To: stable@vger.kernel.org, seanjc@google.com Cc: Jim Mattson , kvm@vger.kernel.org Subject: FAILED: Patch "KVM: x86: Return "unsupported" instead of "invalid" on access to unsupported PV MSR" failed to apply to 6.12-stable tree Date: Sat, 28 Feb 2026 20:19:34 -0500 Message-ID: <20260301011934.1674675-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 5bb9ac1865123356337a389af935d3913ee917ed Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 30 Dec 2025 12:59:48 -0800 Subject: [PATCH] KVM: x86: Return "unsupported" instead of "invalid" on access to unsupported PV MSR Return KVM_MSR_RET_UNSUPPORTED instead of '1' (which for all intents and purposes means "invalid") when rejecting accesses to KVM PV MSRs to adhere to KVM's ABI of allowing host reads and writes of '0' to MSRs that are advertised to userspace via KVM_GET_MSR_INDEX_LIST, even if the vCPU model doesn't support the MSR. E.g. running a QEMU VM with -cpu host,-kvmclock,kvm-pv-enforce-cpuid yields: qemu: error: failed to set MSR 0x12 to 0x0 qemu: target/i386/kvm/kvm.c:3301: kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID") Cc: stable@vger.kernel.org Reviewed-by: Jim Mattson Link: https://patch.msgid.link/20251230205948.4094097-1-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 211d8c24a4b11..e4418409b468d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4097,47 +4097,47 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_WALL_CLOCK_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; vcpu->kvm->arch.wall_clock = data; kvm_write_wall_clock(vcpu->kvm, data, 0); break; case MSR_KVM_WALL_CLOCK: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; vcpu->kvm->arch.wall_clock = data; kvm_write_wall_clock(vcpu->kvm, data, 0); break; case MSR_KVM_SYSTEM_TIME_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; kvm_write_system_time(vcpu, data, false, msr_info->host_initiated); break; case MSR_KVM_SYSTEM_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; kvm_write_system_time(vcpu, data, true, msr_info->host_initiated); break; case MSR_KVM_ASYNC_PF_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_pv_enable_async_pf(vcpu, data)) return 1; break; case MSR_KVM_ASYNC_PF_INT: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_pv_enable_async_pf_int(vcpu, data)) return 1; break; case MSR_KVM_ASYNC_PF_ACK: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (data & 0x1) { /* * Pairs with the smp_mb__after_atomic() in @@ -4150,7 +4150,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_STEAL_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_STEAL_TIME)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (unlikely(!sched_info_on())) return 1; @@ -4168,7 +4168,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_PV_EOI_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_PV_EOI)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_lapic_set_pv_eoi(vcpu, data, sizeof(u8))) return 1; @@ -4176,7 +4176,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; /* only enable bit supported */ if (data & (-1ULL << 1)) @@ -4477,61 +4477,61 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_WALL_CLOCK: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->kvm->arch.wall_clock; break; case MSR_KVM_WALL_CLOCK_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->kvm->arch.wall_clock; break; case MSR_KVM_SYSTEM_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.time; break; case MSR_KVM_SYSTEM_TIME_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.time; break; case MSR_KVM_ASYNC_PF_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.apf.msr_en_val; break; case MSR_KVM_ASYNC_PF_INT: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.apf.msr_int_val; break; case MSR_KVM_ASYNC_PF_ACK: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = 0; break; case MSR_KVM_STEAL_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_STEAL_TIME)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.st.msr_val; break; case MSR_KVM_PV_EOI_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_PV_EOI)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.pv_eoi.msr_val; break; case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.msr_kvm_poll_control; break; -- 2.51.0