Commit 1f568d36 authored by Brijesh Singh's avatar Brijesh Singh Committed by Borislav Petkov (AMD)
Browse files

x86/fault: Add helper for dumping RMP entries 



This information will be useful for debugging things like page faults
due to RMP access violations and RMPUPDATE failures.

  [ mdr: move helper to standalone patch, rework dump logic as suggested
    by Boris. ]

Signed-off-by: default avatarBrijesh Singh <brijesh.singh@amd.com>
Signed-off-by: default avatarAshish Kalra <ashish.kalra@amd.com>
Signed-off-by: default avatarMichael Roth <michael.roth@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-8-michael.roth@amd.com
parent 94b36bc2

arch/x86/include/asm/sev.h

+2 −0
Original line number Diff line number Diff line
@@ -247,9 +247,11 @@ static inline u64 sev_get_status(void) { return 0; } 
#ifdef CONFIG_KVM_AMD_SEV

bool snp_probe_rmptable_info(void);

int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level);

void snp_dump_hva_rmpentry(unsigned long address);

#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; }

static inline void snp_dump_hva_rmpentry(unsigned long address) {}

#endif



#endif

arch/x86/virt/svm/sev.c

+89 −10
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ 
 * Family 19h Model 01h, Rev B1 processor.

 */

struct rmpentry {

	union {

		struct {

			u64 assigned	: 1,

			    pagesize	: 1,

			    immutable	: 1,
@@ -44,7 +46,10 @@ struct rmpentry { 
			    vmsa	: 1,

			    validated	: 1,

			    rsvd2	: 1;

	u64 rsvd3;

		};

		u64 lo;

	};

	u64 hi;

} __packed;



/*
@@ -263,3 +268,77 @@ int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) 
	return 0;

}

EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);



/*

 * Dump the raw RMP entry for a particular PFN. These bits are documented in the

 * PPR for a particular CPU model and provide useful information about how a

 * particular PFN is being utilized by the kernel/firmware at the time certain

 * unexpected events occur, such as RMP faults.

 */

static void dump_rmpentry(u64 pfn)

{

	u64 pfn_i, pfn_end;

	struct rmpentry *e;

	int level;



	e = __snp_lookup_rmpentry(pfn, &level);

	if (IS_ERR(e)) {

		pr_err("Failed to read RMP entry for PFN 0x%llx, error %ld\n",

		       pfn, PTR_ERR(e));

		return;

	}



	if (e->assigned) {

		pr_info("PFN 0x%llx, RMP entry: [0x%016llx - 0x%016llx]\n",

			pfn, e->lo, e->hi);

		return;

	}



	/*

	 * If the RMP entry for a particular PFN is not in an assigned state,

	 * then it is sometimes useful to get an idea of whether or not any RMP

	 * entries for other PFNs within the same 2MB region are assigned, since

	 * those too can affect the ability to access a particular PFN in

	 * certain situations, such as when the PFN is being accessed via a 2MB

	 * mapping in the host page table.

	 */

	pfn_i = ALIGN_DOWN(pfn, PTRS_PER_PMD);

	pfn_end = pfn_i + PTRS_PER_PMD;



	pr_info("PFN 0x%llx unassigned, dumping non-zero entries in 2M PFN region: [0x%llx - 0x%llx]\n",

		pfn, pfn_i, pfn_end);



	while (pfn_i < pfn_end) {

		e = __snp_lookup_rmpentry(pfn_i, &level);

		if (IS_ERR(e)) {

			pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",

			       PTR_ERR(e), pfn_i);

			pfn_i++;

			continue;

		}



		if (e->lo || e->hi)

			pr_info("PFN: 0x%llx, [0x%016llx - 0x%016llx]\n", pfn_i, e->lo, e->hi);

		pfn_i++;

	}

}



void snp_dump_hva_rmpentry(unsigned long hva)

{

	unsigned long paddr;

	unsigned int level;

	pgd_t *pgd;

	pte_t *pte;



	pgd = __va(read_cr3_pa());

	pgd += pgd_index(hva);

	pte = lookup_address_in_pgd(pgd, hva, &level);



	if (!pte) {

		pr_err("Can't dump RMP entry for HVA %lx: no PTE/PFN found\n", hva);

		return;

	}



	paddr = PFN_PHYS(pte_pfn(*pte)) | (hva & ~page_level_mask(level));

	dump_rmpentry(PHYS_PFN(paddr));

}