[PATCH 1/3] KVM: riscv: Pass the target size to huge G-stage checks

[Jinyu Tang]

fault_supports_gstage_huge_mapping() already contains the two checks
needed before installing a G-stage block mapping: the userspace address
and GPA must have matching offsets within the block, and the whole block
must be contained within the memslot.

The helper currently hard-codes PMD_SIZE because its only caller is the
transparent hugepage path. The hugetlb path needs the same checks, but
the target block size can be either PMD_SIZE or PUD_SIZE depending on the
hugetlb VMA.

So pass the target mapping size into the helper and use it for the
alignment and bounds checks. This keeps the existing THP PMD behavior
unchanged and prepares the helper to be reused for the following hugetlb
fix.

Signed-off-by: Jinyu Tang <tjytimi at 163.com>
---
 arch/riscv/kvm/mmu.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 2d3def024..10be8f683 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -286,7 +286,8 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 }
 
 static bool fault_supports_gstage_huge_mapping(struct kvm_memory_slot *memslot,
-					       unsigned long hva)
+					       unsigned long hva,
+					       unsigned long map_size)
 {
 	hva_t uaddr_start, uaddr_end;
 	gpa_t gpa_start;
@@ -300,8 +301,8 @@ static bool fault_supports_gstage_huge_mapping(struct kvm_memory_slot *memslot,
 
 	/*
 	 * Pages belonging to memslots that don't have the same alignment
-	 * within a PMD for userspace and GPA cannot be mapped with g-stage
-	 * PMD entries, because we'll end up mapping the wrong pages.
+	 * within a huge page for userspace and GPA cannot be mapped with
+	 * g-stage block entries, because we'll end up mapping the wrong pages.
 	 *
 	 * Consider a layout like the following:
 	 *
@@ -321,7 +322,7 @@ static bool fault_supports_gstage_huge_mapping(struct kvm_memory_slot *memslot,
 	 *   e -> g
 	 *   f -> h
 	 */
-	if ((gpa_start & (PMD_SIZE - 1)) != (uaddr_start & (PMD_SIZE - 1)))
+	if ((gpa_start & (map_size - 1)) != (uaddr_start & (map_size - 1)))
 		return false;
 
 	/*
@@ -336,7 +337,8 @@ static bool fault_supports_gstage_huge_mapping(struct kvm_memory_slot *memslot,
 	 * userspace_addr or the base_gfn, as both are equally aligned (per
 	 * the check above) and equally sized.
 	 */
-	return (hva >= ALIGN(uaddr_start, PMD_SIZE)) && (hva < ALIGN_DOWN(uaddr_end, PMD_SIZE));
+	return (hva & ~(map_size - 1)) >= uaddr_start &&
+	       (hva & ~(map_size - 1)) + map_size <= uaddr_end;
 }
 
 static int get_hva_mapping_size(struct kvm *kvm,
@@ -404,7 +406,7 @@ static unsigned long transparent_hugepage_adjust(struct kvm *kvm,
 	 * sure that the HVA and GPA are sufficiently aligned and that the
 	 * block map is contained within the memslot.
 	 */
-	if (fault_supports_gstage_huge_mapping(memslot, hva)) {
+	if (fault_supports_gstage_huge_mapping(memslot, hva, PMD_SIZE)) {
 		int sz;
 
 		sz = get_hva_mapping_size(kvm, hva);
-- 
2.43.0