Merge tag 'kvm-x86-fixes-6.11-rcN' of https://github.com/kvm-x86/linux into kvm-master

KVM x86 fixes for 6.11

 - Fixup missed comments from the REMOVED_SPTE=>FROZEN_SPTE rename.

 - Ensure a root is successfully loaded when pre-faulting SPTEs.

 - Grab kvm->srcu when handling KVM_SET_VCPU_EVENTS to guard against accessing
   memslots if toggling SMM happens to force a VM-Exit.

 - Emulate MSR_{FS,GS}_BASE on SVM even though interception is always disabled,
   so that KVM does the right thing if KVM's emulator encounters {RD,WR}MSR.

 - Explicitly clear BUS_LOCK_DETECT from KVM's caps on AMD, as KVM doesn't yet
   virtualize BUS_LOCK_DETECT on AMD.

 - Cleanup the help message for CONFIG_KVM_AMD_SEV, and call out that KVM now
   supports SEV-SNP too.

1 files changed, 30 insertions, 3 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index c9bf68c239a0..45bf05ad5c53 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -944,10 +944,37 @@ static inline bool htlb_allow_alloc_fallback(int reason)
 static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
 					   struct mm_struct *mm, pte_t *pte)
 {
-	if (huge_page_size(h) == PMD_SIZE)
+	const unsigned long size = huge_page_size(h);
+
+	VM_WARN_ON(size == PAGE_SIZE);
+
+	/*
+	 * hugetlb must use the exact same PT locks as core-mm page table
+	 * walkers would. When modifying a PTE table, hugetlb must take the
+	 * PTE PT lock, when modifying a PMD table, hugetlb must take the PMD
+	 * PT lock etc.
+	 *
+	 * The expectation is that any hugetlb folio smaller than a PMD is
+	 * always mapped into a single PTE table and that any hugetlb folio
+	 * smaller than a PUD (but at least as big as a PMD) is always mapped
+	 * into a single PMD table.
+	 *
+	 * If that does not hold for an architecture, then that architecture
+	 * must disable split PT locks such that all *_lockptr() functions
+	 * will give us the same result: the per-MM PT lock.
+	 *
+	 * Note that with e.g., CONFIG_PGTABLE_LEVELS=2 where
+	 * PGDIR_SIZE==P4D_SIZE==PUD_SIZE==PMD_SIZE, we'd use pud_lockptr()
+	 * and core-mm would use pmd_lockptr(). However, in such configurations
+	 * split PMD locks are disabled -- they don't make sense on a single
+	 * PGDIR page table -- and the end result is the same.
+	 */
+	if (size >= PUD_SIZE)
+		return pud_lockptr(mm, (pud_t *) pte);
+	else if (size >= PMD_SIZE || IS_ENABLED(CONFIG_HIGHPTE))
 		return pmd_lockptr(mm, (pmd_t *) pte);
-	VM_BUG_ON(huge_page_size(h) == PAGE_SIZE);
-	return &mm->page_table_lock;
+	/* pte_alloc_huge() only applies with !CONFIG_HIGHPTE */
+	return ptep_lockptr(mm, pte);
 }
 
 #ifndef hugepages_supported