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 <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "Peter Zijlstra (Intel)" <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Brijesh Singh <[email protected]>
---
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
On Wed, Mar 24, 2021 at 10:04 AM Brijesh Singh <[email protected]> wrote:
>
> 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 <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Joerg Roedel <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Tony Luck <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: "Peter Zijlstra (Intel)" <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Tom Lendacky <[email protected]>
> Cc: David Rientjes <[email protected]>
> Cc: Sean Christopherson <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Brijesh Singh <[email protected]>
> ---
> 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);
This is an error path, and I don't think you have any particular
guarantee that virt_to_page(address) is valid. Please add appropriate
validation or use one of the slow lookup helpers.