[PATCH 10/15] KVM: x86/mmu: Implement PWALK_STATUS_READ_ONLY_PTE_GPA in page walker

[Nikolas Wipper]

Implement PWALK_STATUS_READ_ONLY_PTE_GPA in the page walker. This status
flag is set when setting an accessed or dirty bit fails, because the
memory of the page table entry was marked as read-only

Signed-off-by: Nikolas Wipper <nik...@amazon.de>
---
 arch/x86/include/asm/kvm_host.h | 2 ++
 arch/x86/kvm/mmu/paging_tmpl.h  | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1c5aaf55c683..7ac1956f6f9b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -290,6 +290,8 @@ enum x86_intercept_stage;
 #define PWALK_FORCE_SET_ACCESSED       BIT(2)
 #define PWALK_SET_ALL  (PWALK_SET_ACCESSED | PWALK_SET_DIRTY)
 
+#define PWALK_STATUS_READ_ONLY_PTE_GPA BIT(0)
+
 /* apic attention bits */
 #define KVM_APIC_CHECK_VAPIC   0
 /*
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 985a19dda603..0eefa48e0e7f 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -244,8 +244,11 @@ static int FNAME(update_accessed_dirty_bits)(struct 
kvm_vcpu *vcpu,
                 * overwrite the read-only memory to set the accessed and dirty
                 * bits.
                 */
-               if (unlikely(!walker->pte_writable[level - 1]))
+               if (unlikely(!walker->pte_writable[level - 1])) {
+                       if (status)
+                               *status |= PWALK_STATUS_READ_ONLY_PTE_GPA;
                        continue;
+               }
 
                ret = __try_cmpxchg_user(ptep_user, &orig_pte, pte, fault);
                if (ret)
-- 
2.40.1




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