Re: [PATCH] crypto: ccp - Have it depend on AMD_IOMMU
From: Borislav Petkov
Date: Sun Feb 11 2024 - 15:19:09 EST
On Fri, Feb 09, 2024 at 11:51:37AM -0600, Tom Lendacky wrote:
> 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)
Pretty much, except the thunk should say that it is the thunk that gets
called:
#if defined(CONFIG_AMD_IOMMU) && defined(CONFIG_KVM_AMD_SEV)
int amd_iommu_snp_disable(void);
#else
static inline int amd_iommu_snp_disable(void) { return -ENODEV; }
#endif
and return -ENODEV to denote that so that the caller doesn't wonder
what's going on.
> I think this would be better in case these should be referenced
> elsewhere in the future.
However, looking at all that code, its design still looks iffy to me.
iommu_page_make_shared() and amd_iommu_snp_disable() is functionality
which the *IOMMU* provides in order to deal with SEV* guests. So that
functionality should be behind
CONFIG_AMD_IOMMU_SEV
or so, on which all its users depend or select. I'd prefer depend tho.
Putting IOMMU facilities around a KVM Kconfig symbol CONFIG_KVM_AMD_SEV
is simply bad design. There are providers of functionality which is
behind Kconfig symbols and users which depend on those. The current
thing is a hack IMNSVHO.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette