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AJvYcCVs9guufYF5ypCpulBcSpGJY8cYgPg9u7yx/2JHak7uSHuOBE4FKLtfhUtIrs51ggcQtLf+IgRiQJEx@lists.linux.dev X-Gm-Message-State: AOJu0YzHzge5g7xHFfHCyP62YH2+IV2FDHw07yuRVtgmTbTJNKkIfkz5 +HySzezCqpXLdltv1u71UsbSKuNkWxPMAjs5pbqAlIumRIJB6NbGfC/4WSxPYjkBHegjK40dEEJ 2Dg== X-Google-Smtp-Source: AGHT+IFHs7tj+Q54d64NDKOfhfMfAS91bOZEx/8/ugogv1Ut4aJidKZIV/qdikwiSwu5m+q7+e5T4vD0P74= X-Received: from plgi6.prod.google.com ([2002:a17:902:cf06:b0:21c:144d:411b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:daca:b0:215:758c:52e8 with SMTP id d9443c01a7336-21f17a774a7mr66004375ad.12.1738768512794; Wed, 05 Feb 2025 07:15:12 -0800 (PST) Date: Wed, 5 Feb 2025 07:15:11 -0800 In-Reply-To: <1969aa1a-e092-4a48-b4a0-9a50ec2ef3b6@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <1969aa1a-e092-4a48-b4a0-9a50ec2ef3b6@amd.com> Message-ID: Subject: Re: [PATCH v2 4/4] iommu/amd: Enable Host SNP support after enabling IOMMU SNP support From: Sean Christopherson To: Vasant Hegde Cc: Ashish Kalra , pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, thomas.lendacky@amd.com, john.allen@amd.com, herbert@gondor.apana.org.au, davem@davemloft.net, joro@8bytes.org, suravee.suthikulpanit@amd.com, will@kernel.org, robin.murphy@arm.com, michael.roth@amd.com, dionnaglaze@google.com, nikunj@amd.com, ardb@kernel.org, kevinloughlin@google.com, Neeraj.Upadhyay@amd.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-coco@lists.linux.dev, iommu@lists.linux.dev Content-Type: text/plain; charset="us-ascii" On Wed, Feb 05, 2025, Vasant Hegde wrote: > On 1/31/2025 7:18 AM, Sean Christopherson wrote: > > On Fri, Jan 31, 2025, Ashish Kalra wrote: > >> @@ -3426,18 +3431,23 @@ void __init amd_iommu_detect(void) > >> int ret; > >> > >> if (no_iommu || (iommu_detected && !gart_iommu_aperture)) > >> - return; > >> + goto disable_snp; > >> > >> if (!amd_iommu_sme_check()) > >> - return; > >> + goto disable_snp; > >> > >> ret = iommu_go_to_state(IOMMU_IVRS_DETECTED); > >> if (ret) > >> - return; > >> + goto disable_snp; > > > > This handles initial failure, but it won't handle the case where amd_iommu_prepare() > > fails, as the iommu_go_to_state() call from amd_iommu_enable() will get > > short-circuited. I don't see any pleasant options. Maybe this? > > > > diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c > > index c5cd92edada0..436e47f13f8f 100644 > > --- a/drivers/iommu/amd/init.c > > +++ b/drivers/iommu/amd/init.c > > @@ -3318,6 +3318,8 @@ static int __init iommu_go_to_state(enum iommu_init_state state) > > ret = state_next(); > > } > > > > + if (ret && !amd_iommu_snp_en && cc_platform_has(CC_ATTR_HOST_SEV_SNP)) > > I think we should clear when `amd_iommu_snp_en` is true. That doesn't address the case where amd_iommu_prepare() fails, because amd_iommu_snp_en will be %false (it's init value) and the RMP will be uninitialized, i.e. CC_ATTR_HOST_SEV_SNP will be incorrectly left set. And conversely, IMO clearing CC_ATTR_HOST_SEV_SNP after initializing the IOMMU and RMP is wrong as well. Such a host is probably hosted regardless, but from the CPU's perspective, SNP is supported and enabled. > May be below check is enough? > > if (ret && amd_iommu_snp_en)