linux-kernel - Re: [PATCH] crypto: ccp - Have it depend on AMD

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Date: Fri, 9 Feb 2024 11:51:37 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>, Ashish Kalra <ashish.kalra@....com>,
 Michael Roth <michael.roth@....com>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccp - Have it depend on AMD_IOMMU

On 2/7/24 14:47, Borislav Petkov wrote:
> From: "Borislav Petkov (AMD)" <bp@...en8.de>
> 
> sev-dev.c calls code in the AMD IOMMU now but that can't really work if
> latter is not enabled in Kconfig:
> 
>    ld: vmlinux.o: in function `__sev_firmware_shutdown.isra.0':
>    sev-dev.c:(.text+0x2501f0e): undefined reference to `amd_iommu_snp_disable'
>    ld: vmlinux.o: in function `snp_rmptable_init':
>    sev.c:(.init.text+0x26260): undefined reference to `amd_iommu_snp_en'
>    make[2]: *** [scripts/Makefile.vmlinux:37: vmlinux] Error 1
>    make: *** [Makefile:240: __sub-make] Error 2
> 
> Fix those deps.
> 
> Fixes: f366a8dac1b8 ("iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown")
> Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
> ---
>   drivers/crypto/ccp/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/crypto/ccp/Kconfig b/drivers/crypto/ccp/Kconfig
> index 32268e239bf1..f394e45e11ab 100644
> --- a/drivers/crypto/ccp/Kconfig
> +++ b/drivers/crypto/ccp/Kconfig
> @@ -38,7 +38,7 @@ config CRYPTO_DEV_CCP_CRYPTO
>   config CRYPTO_DEV_SP_PSP
>   	bool "Platform Security Processor (PSP) device"
>   	default y
> -	depends on CRYPTO_DEV_CCP_DD && X86_64
> +	depends on CRYPTO_DEV_CCP_DD && X86_64 && AMD_IOMMU

Or should the ifdef around amd_iommu_snp_disable() in 
include/linux/amd-iommu.h instead be:

#if defined(CONFIG_AMD_IOMMU) && defined(CONFIG_KVM_AMD_SEV)

and amd_iommu_snp_en be protected in arch/x86/include/asm/iommu.h as:

#ifdef CONFIG_AMD_IOMMU
extern bool amd_iommu_snp_en;
#else
#define amd_iommu_snp_en false
#endif

I think this would be better in case these should be referenced elsewhere 
in the future.

Thanks,
Tom

>   	help
>   	 Provide support for the AMD Platform Security Processor (PSP).
>   	 The PSP is a dedicated processor that provides support for key