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[213.30.8.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442fd516a51sm36118515e9.24.2025.05.16.07.38.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 May 2025 07:38:33 -0700 (PDT) Message-ID: Date: Fri, 16 May 2025 15:38:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] hw/i386/amd_iommu: Fix xtsup when vcpus < 255 To: Sairaj Kodilkar , qemu-devel@nongnu.org Cc: mst@redhat.com, marcel.apfelbaum@gmail.com, pbonzini@redhat.com, richard.henderson@linaro.org, eduardo@habkost.net, suravee.suthikulpanit@amd.com, alejandro.j.jimenez@oracle.com, joao.m.martins@oracle.com, Vasant Hegde References: <20250516100535.4980-1-sarunkod@amd.com> <20250516100535.4980-3-sarunkod@amd.com> Content-Language: en-US From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <20250516100535.4980-3-sarunkod@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32d; envelope-from=philmd@linaro.org; helo=mail-wm1-x32d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Hi, On 16/5/25 12:05, Sairaj Kodilkar wrote: > From: Vasant Hegde > > If vCPUs > 255 then x86 common code (x86_cpus_init()) call kvm_enable_x2apic(). > But if vCPUs <= 255 then the common code won't calls kvm_enable_x2apic(). > > This is because commit 8c6619f3e692 ("hw/i386/amd_iommu: Simplify non-KVM > checks on XTSup feature") removed the call to kvm_enable_x2apic when xtsup > is "on", which break things when guest is booted with x2apic mode and > there are <= 255 vCPUs. > > Fix this by adding back kvm_enable_x2apic() call when xtsup=on. > > Fixes: 8c6619f3e692 ("hw/i386/amd_iommu: Simplify non-KVM checks on XTSup feature") > Reported-by: Alejandro Jimenez > Tested-by: Tested-by: Alejandro Jimenez > Cc: Philippe Mathieu-Daudé > Cc: Joao Martins > Signed-off-by: Vasant Hegde > Signed-off-by: Sairaj Kodilkar > --- > hw/i386/amd_iommu.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c > index df8ba5d39ada..af85706b8a0d 100644 > --- a/hw/i386/amd_iommu.c > +++ b/hw/i386/amd_iommu.c > @@ -1649,6 +1649,14 @@ static void amdvi_sysbus_realize(DeviceState *dev, Error **errp) > exit(EXIT_FAILURE); > } > > + if (s->xtsup) { I suppose we need: if (s->xtsup && kvm_enabled()) { otherwise that will trigger back the problem I tried to fix. Did you try building QEMU with KVM disabled? > + if (kvm_irqchip_is_split() && !kvm_enable_x2apic()) { > + error_report("AMD IOMMU xtsup=on requires x2APIC support on " > + "the KVM side"); > + exit(EXIT_FAILURE); > + } > + } > + > pci_setup_iommu(bus, &amdvi_iommu_ops, s); > amdvi_init(s); > }