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-rw-r--r--arch/x86/kvm/mmu/tdp_mmu.c112
1 files changed, 112 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 76ebb5898dd7..8accfae76bf6 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -2,6 +2,7 @@
#include "mmu.h"
#include "mmu_internal.h"
+#include "tdp_iter.h"
#include "tdp_mmu.h"
#include "spte.h"
@@ -130,3 +131,114 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
return __pa(root->spt);
}
+
+static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
+ u64 old_spte, u64 new_spte, int level);
+
+/**
+ * handle_changed_spte - handle bookkeeping associated with an SPTE change
+ * @kvm: kvm instance
+ * @as_id: the address space of the paging structure the SPTE was a part of
+ * @gfn: the base GFN that was mapped by the SPTE
+ * @old_spte: The value of the SPTE before the change
+ * @new_spte: The value of the SPTE after the change
+ * @level: the level of the PT the SPTE is part of in the paging structure
+ *
+ * Handle bookkeeping that might result from the modification of a SPTE.
+ * This function must be called for all TDP SPTE modifications.
+ */
+static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
+ u64 old_spte, u64 new_spte, int level)
+{
+ bool was_present = is_shadow_present_pte(old_spte);
+ bool is_present = is_shadow_present_pte(new_spte);
+ bool was_leaf = was_present && is_last_spte(old_spte, level);
+ bool is_leaf = is_present && is_last_spte(new_spte, level);
+ bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
+ u64 *pt;
+ u64 old_child_spte;
+ int i;
+
+ WARN_ON(level > PT64_ROOT_MAX_LEVEL);
+ WARN_ON(level < PG_LEVEL_4K);
+ WARN_ON(gfn % KVM_PAGES_PER_HPAGE(level));
+
+ /*
+ * If this warning were to trigger it would indicate that there was a
+ * missing MMU notifier or a race with some notifier handler.
+ * A present, leaf SPTE should never be directly replaced with another
+ * present leaf SPTE pointing to a differnt PFN. A notifier handler
+ * should be zapping the SPTE before the main MM's page table is
+ * changed, or the SPTE should be zeroed, and the TLBs flushed by the
+ * thread before replacement.
+ */
+ if (was_leaf && is_leaf && pfn_changed) {
+ pr_err("Invalid SPTE change: cannot replace a present leaf\n"
+ "SPTE with another present leaf SPTE mapping a\n"
+ "different PFN!\n"
+ "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d",
+ as_id, gfn, old_spte, new_spte, level);
+
+ /*
+ * Crash the host to prevent error propagation and guest data
+ * courruption.
+ */
+ BUG();
+ }
+
+ if (old_spte == new_spte)
+ return;
+
+ /*
+ * The only times a SPTE should be changed from a non-present to
+ * non-present state is when an MMIO entry is installed/modified/
+ * removed. In that case, there is nothing to do here.
+ */
+ if (!was_present && !is_present) {
+ /*
+ * If this change does not involve a MMIO SPTE, it is
+ * unexpected. Log the change, though it should not impact the
+ * guest since both the former and current SPTEs are nonpresent.
+ */
+ if (WARN_ON(!is_mmio_spte(old_spte) && !is_mmio_spte(new_spte)))
+ pr_err("Unexpected SPTE change! Nonpresent SPTEs\n"
+ "should not be replaced with another,\n"
+ "different nonpresent SPTE, unless one or both\n"
+ "are MMIO SPTEs.\n"
+ "as_id: %d gfn: %llx old_spte: %llx new_spte: %llx level: %d",
+ as_id, gfn, old_spte, new_spte, level);
+ return;
+ }
+
+
+ if (was_leaf && is_dirty_spte(old_spte) &&
+ (!is_dirty_spte(new_spte) || pfn_changed))
+ kvm_set_pfn_dirty(spte_to_pfn(old_spte));
+
+ /*
+ * Recursively handle child PTs if the change removed a subtree from
+ * the paging structure.
+ */
+ if (was_present && !was_leaf && (pfn_changed || !is_present)) {
+ pt = spte_to_child_pt(old_spte, level);
+
+ for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
+ old_child_spte = READ_ONCE(*(pt + i));
+ WRITE_ONCE(*(pt + i), 0);
+ handle_changed_spte(kvm, as_id,
+ gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
+ old_child_spte, 0, level - 1);
+ }
+
+ kvm_flush_remote_tlbs_with_address(kvm, gfn,
+ KVM_PAGES_PER_HPAGE(level));
+
+ free_page((unsigned long)pt);
+ }
+}
+
+static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
+ u64 old_spte, u64 new_spte, int level)
+{
+ __handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level);
+}