linux-kernel - Re: [PATCH v10 06/50] x86/sev: Add the host SEV-SNP initialization support

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Message-ID: <20231107202757.GEZUqdzYyzVBHTBhZX@fat_crate.local>
Date:   Tue, 7 Nov 2023 21:27:57 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kalra, Ashish" <ashish.kalra@....com>
Cc:     Michael Roth <michael.roth@....com>, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
        dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
        peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
        rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
        vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        jarkko@...nel.org, nikunj.dadhania@....com, pankaj.gupta@....com,
        liam.merwick@...cle.com, zhi.a.wang@...el.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v10 06/50] x86/sev: Add the host SEV-SNP initialization
 support

On Tue, Nov 07, 2023 at 08:19:31PM +0100, Borislav Petkov wrote:
> Arch code does not call drivers - arch code sets up the arch and
> provides facilities which the drivers use.

IOW (just an example diff):

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 1c9924de607a..00cdbc844961 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3290,6 +3290,7 @@ static int __init state_next(void)
 		break;
 	case IOMMU_ENABLED:
 		register_syscore_ops(&amd_iommu_syscore_ops);
+		amd_iommu_snp_enable();
 		ret = amd_iommu_init_pci();
 		init_state = ret ? IOMMU_INIT_ERROR : IOMMU_PCI_INIT;
 		break;
@@ -3814,16 +3815,6 @@ int amd_iommu_snp_enable(void)
 		return -EINVAL;
 	}
 
-	/*
-	 * Prevent enabling SNP after IOMMU_ENABLED state because this process
-	 * affect how IOMMU driver sets up data structures and configures
-	 * IOMMU hardware.
-	 */
-	if (init_state > IOMMU_ENABLED) {
-		pr_err("SNP: Too late to enable SNP for IOMMU.\n");
-		return -EINVAL;
-	}
-
 	amd_iommu_snp_en = check_feature_on_all_iommus(FEATURE_SNP);
 	if (!amd_iommu_snp_en)
 		return -EINVAL;

and now you only need to line up snp_rmptable_init() after IOMMU init
instead of having it be a fs_initcall which happens right after
pci_subsys_init() so that PCI is there but at the right time when iommu
init state is at IOMMU_ENABLED but no later because then it is too late.

And there you need to test amd_iommu_snp_en which is already exported
anyway.

Ok?

-- 
Regards/Gruss,
    Boris.

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