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 2C2EB47CC62; Sat, 28 Feb 2026 17:55:12 +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=1772301312; cv=none; b=lJ2tjMF1dW/c5b5lsaOpJiFuzoaC/wgXoNXRcBFnYTqm5LqCBfCiUh/eUER9XFJNJnkVNBRaRB3xXm+XEMPbrev81011GAtVT1BUIQmvygabREIX82VqTNwLTrAK0+l+SX/W+zeWZQ8qIoR1hPWsXY/2X68Yn37Iq4lDOh48kpc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772301312; c=relaxed/simple; bh=3kbo5eabQVn/8jsbQHi8bNNF8ZkEN2sFUSWSGR+8m5k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PBHgf9rO7GaXJ9c/76leQC+Kaf/n2qx5EnI3zm8eciWMMXWNFMbYjlhDz11eWuz96iWhABF9Krc9H6AJ1klJ2yyHnWxApsJR8V3qa+ZhHJExxJi2kvfxpBTDq2UkdBzx5228Wpfh2X5VZ3TZ5xJTL75lXBn1d7L/jkz5DPvmp+c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HcgkNXSQ; 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="HcgkNXSQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C0F5C116D0; Sat, 28 Feb 2026 17:55:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772301312; bh=3kbo5eabQVn/8jsbQHi8bNNF8ZkEN2sFUSWSGR+8m5k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HcgkNXSQqSL1mdUVAQ4ufU7Rzm1Tde60Q2R3cj0Wkut53OQFRUtbulbHMQFB37rcE YGsm69zE3S6FeJsuzcYAwKY0vOq6lORUKdJ1bgm4VDfpQqutFBBGdfdEISssM9dyDi WcJNPHLiu+O6xrm7w7Cs45mi8z1GJDYumVU8058Sq/CWcvz4FV8piLCPYZCkEsVQ6b 6BZJz9a2go+HGDnxaBsuZWZyfd4oHFWFW6zMQWIz/vsfld1uGYyiqoOaQo2FmX7A9d /ev41jcC9T3b25jQyfe5SKHF6ql48vovyHZqlPDL5LpC/6wuUlpegJvrwPQedoN86T /tOTLsxVqEE5w== From: Sasha Levin To: patches@lists.linux.dev Cc: Sean Christopherson , stable@vger.kernel.org, Jim Mattson , Sasha Levin Subject: [PATCH 6.18 497/752] KVM: x86: Return "unsupported" instead of "invalid" on access to unsupported PV MSR Date: Sat, 28 Feb 2026 12:43:28 -0500 Message-ID: <20260228174750.1542406-497-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228174750.1542406-1-sashal@kernel.org> References: <20260228174750.1542406-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit 5bb9ac1865123356337a389af935d3913ee917ed ] 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 Signed-off-by: Sasha Levin --- 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 c075ee23aeade..79d0abaf71dde 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4136,47 +4136,47 @@ 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) { vcpu->arch.apf.pageready_pending = false; kvm_check_async_pf_completion(vcpu); @@ -4184,7 +4184,7 @@ 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; @@ -4202,7 +4202,7 @@ 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; @@ -4210,7 +4210,7 @@ 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)) @@ -4511,61 +4511,61 @@ 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