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x86/sev: Introduce an SNP leaked pages list

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Pages are unsafe to be released back to the page-allocator if they
have been transitioned to firmware/guest state and can't be reclaimed
or transitioned back to hypervisor/shared state. In this case, add them
to an internal leaked pages list to ensure that they are not freed or
touched/accessed to cause fatal page faults.

  [ mdr: Relocate to arch/x86/virt/svm/sev.c ]

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20240126041126.1927228-16-michael.roth@amd.com
This commit is contained in:
Ashish Kalra 2024-01-25 22:11:15 -06:00 committed by Borislav Petkov (AMD)
parent 18085ac2f2
commit 8dac642999
2 changed files with 39 additions and 0 deletions
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2
arch/x86/include/asm/sev.h
View File

@ -264,6 +264,7 @@ void snp_dump_hva_rmpentry(unsigned long address);
int psmash(u64 pfn);
int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 asid, bool immutable);
int rmp_make_shared(u64 pfn, enum pg_level level);
void snp_leak_pages(u64 pfn, unsigned int npages);
#else
static inline bool snp_probe_rmptable_info(void) { return false; }
static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; }
@ -275,6 +276,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 as
return -ENODEV;
}
static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
#endif
#endif

37
arch/x86/virt/svm/sev.c
View File

@ -65,6 +65,11 @@ static u64 probed_rmp_base, probed_rmp_size;
static struct rmpentry *rmptable __ro_after_init;
static u64 rmptable_max_pfn __ro_after_init;
static LIST_HEAD(snp_leaked_pages_list);
static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
static unsigned long snp_nr_leaked_pages;
#undef pr_fmt
#define pr_fmt(fmt) "SEV-SNP: " fmt
@ -515,3 +520,35 @@ int rmp_make_shared(u64 pfn, enum pg_level level)
return rmpupdate(pfn, &state);
}
EXPORT_SYMBOL_GPL(rmp_make_shared);
void snp_leak_pages(u64 pfn, unsigned int npages)
{
struct page *page = pfn_to_page(pfn);
pr_warn("Leaking PFN range 0x%llx-0x%llx\n", pfn, pfn + npages);
spin_lock(&snp_leaked_pages_list_lock);
while (npages--) {
/*
* Reuse the page's buddy list for chaining into the leaked
* pages list. This page should not be on a free list currently
* and is also unsafe to be added to a free list.
*/
if (likely(!PageCompound(page)) ||
/*
* Skip inserting tail pages of compound page as
* page->buddy_list of tail pages is not usable.
*/
(PageHead(page) && compound_nr(page) <= npages))
list_add_tail(&page->buddy_list, &snp_leaked_pages_list);
dump_rmpentry(pfn);
snp_nr_leaked_pages++;
pfn++;
page++;
}
spin_unlock(&snp_leaked_pages_list_lock);
}
EXPORT_SYMBOL_GPL(snp_leak_pages);