[PATCH RFC v9 10/51] x86/fault: Add helper for dumping RMP entries

Michael Roth
2023-06-12T04:28:17Z

From: Brijesh Singh <brijesh.singh@amd.com>

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@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: move helper to standalone patch]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
arch/x86/coco/sev/host.c | 43 +++++++++++++++++++++++++++++++++
arch/x86/include/asm/sev-host.h | 2 ++
2 files changed, 45 insertions(+)

diff --git a/arch/x86/coco/sev/host.c b/arch/x86/coco/sev/host.c
index 0cc5a6d11b25..d766b3bc6647 100644
--- a/arch/x86/coco/sev/host.c
+++ b/arch/x86/coco/sev/host.c
@@ -295,3 +295,46 @@ int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
return 0;
}
EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
+
+void sev_dump_rmpentry(u64 pfn)
+{
+ unsigned long pfn_end;
+ struct rmpentry e;
+ int level, ret;
+
+ ret = __snp_lookup_rmpentry(pfn, &e, &level);
+ if (ret) {
+ pr_info("Failed to read RMP entry for PFN 0x%llx, error %d\n", pfn, ret);
+ return;
+ }
+
+ if (rmpentry_assigned(&e)) {
+ pr_info("RMPEntry paddr 0x%llx: [high=0x%016llx low=0x%016llx]\n",
+ pfn << PAGE_SHIFT, e.high, e.low);
+ return;
+ }
+
+ /*
+ * If the RMP entry at the faulting pfn was not assigned, then not sure
+ * what caused the RMP violation. To get some useful debug information,
+ * iterate through the entire 2MB region, and dump the RMP entries if
+ * one of the bit in the RMP entry is set.
+ */
+ pfn = pfn & ~(PTRS_PER_PMD - 1);
+ pfn_end = pfn + PTRS_PER_PMD;
+
+ while (pfn < pfn_end) {
+ ret = __snp_lookup_rmpentry(pfn, &e, &level);
+ if (ret) {
+ pr_info("Failed to read RMP entry for PFN 0x%llx\n", pfn);
+ pfn++;
+ continue;
+ }
+
+ if (e.low || e.high)
+ pr_info("RMPEntry paddr 0x%llx: [high=0x%016llx low=0x%016llx]\n",
+ pfn << PAGE_SHIFT, e.high, e.low);
+ pfn++;
+ }
+}
+EXPORT_SYMBOL_GPL(sev_dump_rmpentry);
diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
index 30d47e20081d..85cfe577155c 100644
--- a/arch/x86/include/asm/sev-host.h
+++ b/arch/x86/include/asm/sev-host.h
@@ -15,8 +15,10 @@

#ifdef CONFIG_KVM_AMD_SEV
int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level);
+void sev_dump_rmpentry(u64 pfn);
#else
static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return 0; }
+static inline void sev_dump_rmpentry(u64 pfn) {}
#endif

#endif
--
2.25.1