Messages in this thread | | | Date | Fri, 24 Nov 2023 15:20:43 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v10 12/50] x86/sev: Invalidate pages from the direct map when adding them to the RMP table |
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On Mon, Oct 16, 2023 at 08:27:41AM -0500, Michael Roth wrote: > From: Brijesh Singh <brijesh.singh@amd.com> > > The integrity guarantee of SEV-SNP is enforced through the RMP table. > The RMP is used with standard x86 and IOMMU page tables to enforce > memory restrictions and page access rights. The RMP check is enforced as > soon as SEV-SNP is enabled globally in the system. When hardware > encounters an RMP-check failure, it raises a page-fault exception. > > The rmp_make_private() and rmp_make_shared() helpers are used to add > or remove the pages from the RMP table. Improve the rmp_make_private() > to invalidate state so that pages cannot be used in the direct-map after > they are added the RMP table, and restored to their default valid > permission after the pages are removed from the RMP table.
Brijesh's SOB comes
<--- here,
then Ashish's two tags.
Please audit your whole set for such inconsistencies.
> @@ -404,6 +440,21 @@ static int rmpupdate(u64 pfn, struct rmp_state *val) > if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) > return -ENXIO; > > + level = RMP_TO_X86_PG_LEVEL(val->pagesize); > + npages = page_level_size(level) / PAGE_SIZE; > + > + /* > + * If page is getting assigned in the RMP table then unmap it from the > + * direct map.
Here I'm missing the explanation *why* the pages need to be unmapped from the direct map.
What happens if not?
> + */ > + if (val->assigned) { > + if (invalidate_direct_map(pfn, npages)) { > + pr_err("Failed to unmap %d pages at pfn 0x%llx from the direct_map\n", > + npages, pfn);
invalidate_direct_map() already dumps an error message - no need to do that here too.
> + return -EFAULT; > + } > + } > + > do { > /* Binutils version 2.36 supports the RMPUPDATE mnemonic. */ > asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE" > @@ -422,6 +473,17 @@ static int rmpupdate(u64 pfn, struct rmp_state *val) > return -EFAULT; > } > > + /* > + * Restore the direct map after the page is removed from the RMP table. > + */ > + if (!val->assigned) { > + if (restore_direct_map(pfn, npages)) { > + pr_err("Failed to map %d pages at pfn 0x%llx into the direct_map\n", > + npages, pfn);
Ditto.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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