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Date: Fri, 13 Jan 2023 17:49:13 -0600
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Alper Gun <alpergun@...gle.com>,
Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
luto@...nel.org, dave.hansen@...ux.intel.com, slp@...hat.com,
pgonda@...gle.com, peterz@...radead.org,
srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
dovmurik@...ux.ibm.com, tobin@....com, bp@...en8.de,
vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
tony.luck@...el.com, marcorr@...gle.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, dgilbert@...hat.com,
jarkko@...nel.org, harald@...fian.com,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v7 23/64] x86/fault: Add support to dump RMP entry on
fault
On 1/13/2023 4:56 PM, Alper Gun wrote:
> On Wed, Dec 14, 2022 at 11:52 AM Michael Roth <michael.roth@....com> wrote:
>>
>> From: Brijesh Singh <brijesh.singh@....com>
>>
>> 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@....com>
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>> Signed-off-by: Michael Roth <michael.roth@....com>
>> ---
>> 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)) {
>
Yes, this needs to be fixed to 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;
Again, this is correct, but then it should be :
if (IS_ERR(e)) {
pfn++;
continue;
}
Thanks,
Ashish
>> +
>> + 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
>>
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