If hardware detects an RMP violation, it will raise a page-fault exception
with the RMP bit set. To help the debug, dump the RMP entry of the faulting
address.

Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Joerg Roedel <jroe...@suse.de>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: "Peter Zijlstra (Intel)" <pet...@infradead.org>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Tom Lendacky <thomas.lenda...@amd.com>
Cc: David Rientjes <rient...@google.com>
Cc: Sean Christopherson <sea...@google.com>
Cc: x...@kernel.org
Cc: k...@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
 arch/x86/mm/fault.c | 75 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f39b551f89a6..7605e06a6dd9 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -31,6 +31,7 @@
 #include <asm/pgtable_areas.h>         /* VMALLOC_START, ...           */
 #include <asm/kvm_para.h>              /* kvm_handle_async_pf          */
 #include <asm/vdso.h>                  /* fixup_vdso_exception()       */
+#include <asm/sev-snp.h>               /* lookup_rmpentry ...          */
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -147,6 +148,76 @@ is_prefetch(struct pt_regs *regs, unsigned long 
error_code, unsigned long addr)
 DEFINE_SPINLOCK(pgd_lock);
 LIST_HEAD(pgd_list);
 
+static void dump_rmpentry(struct page *page, rmpentry_t *e)
+{
+       unsigned long paddr = page_to_pfn(page) << PAGE_SHIFT;
+
+       pr_alert("RMPEntry paddr 0x%lx [assigned=%d immutable=%d pagesize=%d 
gpa=0x%lx asid=%d "
+               "vmsa=%d validated=%d]\n", paddr, rmpentry_assigned(e), 
rmpentry_immutable(e),
+               rmpentry_pagesize(e), rmpentry_gpa(e), rmpentry_asid(e), 
rmpentry_vmsa(e),
+               rmpentry_validated(e));
+       pr_alert("RMPEntry paddr 0x%lx %016llx %016llx\n", paddr, e->high, 
e->low);
+}
+
+static void show_rmpentry(unsigned long address)
+{
+       struct page *page = virt_to_page(address);
+       rmpentry_t *entry, *large_entry;
+       int level, rmp_level;
+       pgd_t *pgd;
+       pte_t *pte;
+
+       /* Get the RMP entry for the fault address */
+       entry = lookup_page_in_rmptable(page, &rmp_level);
+       if (!entry) {
+               pr_alert("SEV-SNP: failed to read RMP entry for address 
0x%lx\n", address);
+               return;
+       }
+
+       dump_rmpentry(page, entry);
+
+       /*
+        * If fault occurred during the large page walk, dump the RMP entry at 
base of 2MB page.
+        */
+       pgd = __va(read_cr3_pa());
+       pgd += pgd_index(address);
+       pte = lookup_address_in_pgd(pgd, address, &level);
+       if ((level > PG_LEVEL_4K) && (!IS_ALIGNED(address, PMD_SIZE))) {
+               address = address & PMD_MASK;
+               large_entry = lookup_page_in_rmptable(virt_to_page(address), 
&rmp_level);
+               if (!large_entry) {
+                       pr_alert("SEV-SNP: failed to read large RMP entry 
0x%lx\n",
+                               address & PMD_MASK);
+                       return;
+               }
+
+               dump_rmpentry(virt_to_page(address), large_entry);
+       }
+
+       /*
+        * If the RMP entry at the faulting address was not assigned, then dump 
may not provide
+        * any 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.
+        */
+       if (!rmpentry_assigned(entry)) {
+               unsigned long start, end;
+
+               start = address & PMD_MASK;
+               end = start + PMD_SIZE;
+
+               for (; start < end; start += PAGE_SIZE) {
+                       entry = lookup_page_in_rmptable(virt_to_page(start), 
&rmp_level);
+                       if (!entry)
+                               return;
+
+                       /* If any of the bits in RMP entry is set then dump it 
*/
+                       if (entry->high || entry->low)
+                               pr_alert("RMPEntry paddr %lx: %016llx 
%016llx\n",
+                                       page_to_pfn(page) << PAGE_SHIFT, 
entry->high, entry->low);
+               }
+       }
+}
+
 #ifdef CONFIG_X86_32
 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
 {
@@ -580,6 +651,10 @@ show_fault_oops(struct pt_regs *regs, unsigned long 
error_code, unsigned long ad
        }
 
        dump_pagetable(address);
+
+       if (error_code & X86_PF_RMP)
+               show_rmpentry(address);
+
 }
 
 static noinline void
-- 
2.17.1

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