Re: [PATCH v1 07/26] x86/fault: Add helper for dumping RMP entries

Borislav Petkov
2024-01-10T11:14:32Z

On Sat, Dec 30, 2023 at 10:19:35AM -0600, Michael Roth wrote:
> + 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);
> +}

Ok, I went and reworked this, see below.

Yes, I think it is important - at least in the beginning - to dump the
whole 2M PFN region for debugging purposes. If that output starts
becoming too unwieldy and overflowing terminals or log files, we'd
shorten it or put it behind a debug option or so.

Thx.

---
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index a8cf33b7da71..259a1dd655a7 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -35,16 +35,21 @@
* Family 19h Model 01h, Rev B1 processor.
*/
struct rmpentry {
- u64 assigned : 1,
- pagesize : 1,
- immutable : 1,
- rsvd1 : 9,
- gpa : 39,
- asid : 10,
- vmsa : 1,
- validated : 1,
- rsvd2 : 1;
- u64 rsvd3;
+ union {
+ struct {
+ u64 assigned : 1,
+ pagesize : 1,
+ immutable : 1,
+ rsvd1 : 9,
+ gpa : 39,
+ asid : 10,
+ vmsa : 1,
+ validated : 1,
+ rsvd2 : 1;
+ };
+ u64 lo;
+ };
+ u64 hi;
} __packed;

/*
@@ -272,22 +277,20 @@ EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
*/
static void dump_rmpentry(u64 pfn)
{
- u64 pfn_current, pfn_end;
+ u64 pfn_i, 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));
+ pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",
+ PTR_ERR(e), pfn);
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]);
+ pr_info("PFN 0x%llx, RMP entry: [0x%016llx - 0x%016llx]\n",
+ pfn, e->lo, e->hi);
return;
}

@@ -299,27 +302,28 @@ static void dump_rmpentry(u64 pfn)
* 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;
+ pfn_i = ALIGN(pfn, PTRS_PER_PMD);
+ pfn_end = pfn_i + PTRS_PER_PMD;

- while (pfn_current < pfn_end) {
- e = __snp_lookup_rmpentry(pfn_current, &level);
+ pr_info("PFN 0x%llx unassigned, dumping the whole 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)) {
- pfn_current++;
+ pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",
+ PTR_ERR(e), pfn_i);
+ pfn_i++;
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++;
- }
+ if (e->lo || e->hi)
+ pr_info("PFN: 0x%llx, [0x%016llx - 0x%016llx]\n", pfn_i, e->lo, e->hi);
+ else
+ pr_info("PFN: 0x%llx ...\n", pfn_i);

- pr_info("No populated RMP entries in the 2MB region containing PFN 0x%llx\n",
- pfn);
+ pfn_i++;
+ }
}

void snp_dump_hva_rmpentry(unsigned long hva)
@@ -339,4 +343,3 @@ void snp_dump_hva_rmpentry(unsigned long hva)

dump_rmpentry(pte_pfn(*pte));
}
-EXPORT_SYMBOL_GPL(snp_dump_hva_rmpentry);

--
Regards/Gruss,
Boris.