On Wed, Dec 14, 2022 at 11:52 AM Michael Roth <michael.roth@xxxxxxx> wrote:
>
> From: Brijesh Singh <brijesh.singh@xxxxxxx>
>
> When SEV-SNP is enabled globally, a write from the host goes through the
> RMP check. If the hardware encounters the check failure, then it raises
> the #PF (with RMP set). Dump the RMP entry at the faulting pfn to help
> the debug.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
> arch/x86/include/asm/sev.h | 2 ++
> arch/x86/kernel/sev.c | 43 ++++++++++++++++++++++++++++++++++++++
> arch/x86/mm/fault.c | 7 ++++++-
> 3 files changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index 4eeedcaca593..2916f4150ac7 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -215,6 +215,7 @@ int snp_lookup_rmpentry(u64 pfn, int *level);
> int psmash(u64 pfn);
> int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
> int rmp_make_shared(u64 pfn, enum pg_level level);
> +void sev_dump_rmpentry(u64 pfn);
> #else
> static inline void sev_es_ist_enter(struct pt_regs *regs) { }
> static inline void sev_es_ist_exit(void) { }
> @@ -247,6 +248,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int as
> return -ENODEV;
> }
> static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
> +static inline void sev_dump_rmpentry(u64 pfn) {}
> #endif
>
> #endif
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index e2b38c3551be..1dd1b36bdfea 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -2508,6 +2508,49 @@ static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
> return entry;
> }
>
> +void sev_dump_rmpentry(u64 pfn)
> +{
> + unsigned long pfn_end;
> + struct rmpentry *e;
> + int level;
> +
> + e = __snp_lookup_rmpentry(pfn, &level);
> + if (!e) {
if (IS_ERR(e)) {
> + pr_info("failed to read RMP entry pfn 0x%llx\n", pfn);
> + return;
> + }
> +
> + if (rmpentry_assigned(e)) {
> + pr_info("RMPEntry paddr 0x%llx [assigned=%d immutable=%d pagesize=%d gpa=0x%lx"
> + " asid=%d vmsa=%d validated=%d]\n", pfn << PAGE_SHIFT,
> + rmpentry_assigned(e), e->info.immutable, rmpentry_pagesize(e),
> + (unsigned long)e->info.gpa, e->info.asid, e->info.vmsa,
> + e->info.validated);
> + 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) {
> + e = __snp_lookup_rmpentry(pfn, &level);
> + if (!e)
> + return;
if (IS_ERR(e))
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);
> +
> /*
> * Return 1 if the RMP entry is assigned, 0 if it exists but is not assigned,
> * and -errno if there is no corresponding RMP entry.
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index ded53879f98d..f2b16dcfbd9a 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -536,6 +536,8 @@ static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
> static void
> show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address)
> {
> + unsigned long pfn;
> +
> if (!oops_may_print())
> return;
>
> @@ -608,7 +610,10 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
> show_ldttss(&gdt, "TR", tr);
> }
>
> - dump_pagetable(address);
> + pfn = dump_pagetable(address);
> +
> + if (error_code & X86_PF_RMP)
> + sev_dump_rmpentry(pfn);
> }
>
> static noinline void
> --
> 2.25.1
>
