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Tue, 15 Apr 2025 04:42:35 -0700 (PDT) Received: from [192.168.10.48] ([176.206.109.83]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-43f2338db88sm208832245e9.6.2025.04.15.04.42.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Apr 2025 04:42:34 -0700 (PDT) Message-ID: <1b29eed0-fafc-427b-bd70-5dd087f2c0dd@redhat.com> Date: Tue, 15 Apr 2025 13:42:33 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/67] iommu/amd: WARN if KVM attempts to set vCPU affinity without posted intrrupts To: Sean Christopherson , Sairaj Kodilkar Cc: Joerg Roedel , David Woodhouse , Lu Baolu , kvm@vger.kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Maxim Levitsky , Joao Martins , David Matlack , Naveen N Rao , Vasant Hegde References: <20250404193923.1413163-1-seanjc@google.com> <20250404193923.1413163-7-seanjc@google.com> <0895007e-95d9-410e-8b24-d17172b0b908@amd.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/11/25 16:10, Sean Christopherson wrote: > On Fri, Apr 11, 2025, Sairaj Kodilkar wrote: >> On 4/5/2025 1:08 AM, Sean Christopherson wrote: >>> WARN if KVM attempts to set vCPU affinity when posted interrupts aren't >>> enabled, as KVM shouldn't try to enable posting when they're unsupported, >>> and the IOMMU driver darn well should only advertise posting support when >>> AMD_IOMMU_GUEST_IR_VAPIC() is true. >>> >>> Note, KVM consumes is_guest_mode only on success. >>> >>> Signed-off-by: Sean Christopherson >>> --- >>> drivers/iommu/amd/iommu.c | 13 +++---------- >>> 1 file changed, 3 insertions(+), 10 deletions(-) >>> >>> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c >>> index b3a01b7757ee..4f69a37cf143 100644 >>> --- a/drivers/iommu/amd/iommu.c >>> +++ b/drivers/iommu/amd/iommu.c >>> @@ -3852,19 +3852,12 @@ static int amd_ir_set_vcpu_affinity(struct irq_data *data, void *vcpu_info) >>> if (!dev_data || !dev_data->use_vapic) >>> return -EINVAL; >>> + if (WARN_ON_ONCE(!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir))) >>> + return -EINVAL; >>> + >> >> Hi Sean, >> 'dev_data->use_vapic' is always zero when AMD IOMMU uses legacy >> interrupts i.e. when AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) is 0. >> Hence you can remove this additional check. > > Hmm, or move it above? KVM should never call amd_ir_set_vcpu_affinity() if > IRQ posting is unsupported, and that would make this consistent with the end > behavior of amd_iommu_update_ga() and amd_iommu_{de,}activate_guest_mode(). > > if (WARN_ON_ONCE(!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir))) > return -EINVAL; > > if (ir_data->iommu == NULL) > return -EINVAL; > > dev_data = search_dev_data(ir_data->iommu, irte_info->devid); > > /* Note: > * This device has never been set up for guest mode. > * we should not modify the IRTE > */ > if (!dev_data || !dev_data->use_vapic) > return -EINVAL; > > I'd like to keep the WARN so that someone will notice if KVM screws up. Makes sense, avic_pi_update_irte() returns way before it has the occasion to call irq_set_vcpu_affinity(). Paolo