On 12/30/23 10:19, Michael Roth wrote:
From: Brijesh Singh <brijesh.singh@xxxxxxx> This information will be useful for debugging things like page faults due to RMP access violations and RMPUPDATE failures. Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx> [mdr: move helper to standalone patch, rework dump logic to reduce verbosity] Signed-off-by: Michael Roth <michael.roth@xxxxxxx> --- arch/x86/include/asm/sev.h | 2 + arch/x86/virt/svm/sev.c | 77 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 79 insertions(+) diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 01ce61b283a3..2c53e3de0b71 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -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#endifdiff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c index 49fdfbf4e518..7c9ced8911e9 100644 --- a/arch/x86/virt/svm/sev.c +++ b/arch/x86/virt/svm/sev.c @@ -266,3 +266,80 @@ 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_current, pfn_end; + struct rmpentry *e; + u64 *e_data; + int level; + + e = __snp_lookup_rmpentry(pfn, &level); + if (IS_ERR(e)) { + pr_info("Failed to read RMP entry for PFN 0x%llx, error %ld\n", + pfn, PTR_ERR(e)); + return; + } + + e_data = (u64 *)e; + if (e->assigned) { + pr_info("RMP entry for PFN 0x%llx: [high=0x%016llx low=0x%016llx]\n", + pfn, e_data[1], e_data[0]); + 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_current = ALIGN(pfn, PTRS_PER_PMD); + pfn_end = pfn_current + PTRS_PER_PMD; + + while (pfn_current < pfn_end) { + e = __snp_lookup_rmpentry(pfn_current, &level); + if (IS_ERR(e)) { + pfn_current++; + continue; + } + + e_data = (u64 *)e; + if (e_data[0] || e_data[1]) { + pr_info("No assigned RMP entry for PFN 0x%llx, but the 2MB region contains populated RMP entries, e.g.: PFN 0x%llx: [high=0x%016llx low=0x%016llx]\n", + pfn, pfn_current, e_data[1], e_data[0]); + return; + } + pfn_current++; + } + + pr_info("No populated RMP entries in the 2MB region containing PFN 0x%llx\n", + pfn); +} + +void snp_dump_hva_rmpentry(unsigned long hva) +{ + 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_info("Can't dump RMP entry for HVA %lx: no PTE/PFN found\n", hva); + return; + } + + dump_rmpentry(pte_pfn(*pte));
Already worked with Mike offline when I was running into issues using this function. Net of that conversation is that the PFN needs to be adjusted using the address offset if the PTE level indicates a huge page.
Additionally the loop in dump_rmpentry() needs to use ALIGN_DOWN() in order to get the PFN of the starting 2MB area.
Thanks, Tom
+} +EXPORT_SYMBOL_GPL(snp_dump_hva_rmpentry);
