[PATCH 4/4] KVM: arm64: Add support for PUD hugepages at stage 2

Christoffer Dall [off-list ref] writes:

On Fri, Apr 20, 2018 at 03:54:09PM +0100, Punit Agrawal wrote:

quoted

KVM only supports PMD hugepages at stage 2. Extend the stage 2 fault
handling to add support for PUD hugepages.

Addition of pud hugepage support enables additional hugepage
sizes (e.g., 1G with 4K granule) which can be useful on cores that
support mapping larger block sizes in the TLB entries.

Signed-off-by: Punit Agrawal <redacted>
Cc: Christoffer Dall <redacted>
Cc: Marc Zyngier <redacted>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
---
 arch/arm/include/asm/kvm_mmu.h         | 19 +++++++++
 arch/arm64/include/asm/kvm_mmu.h       | 15 +++++++
 arch/arm64/include/asm/pgtable-hwdef.h |  4 ++
 arch/arm64/include/asm/pgtable.h       |  2 +
 virt/kvm/arm/mmu.c                     | 54 ++++++++++++++++++++------
 5 files changed, 83 insertions(+), 11 deletions(-)

[...]

quoted

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c

[...]

quoted

@@ -1452,9 +1472,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	}
 
 	vma_pagesize = vma_kernel_pagesize(vma);
-	if (vma_pagesize == PMD_SIZE && !logging_active) {
+	if ((vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE) &&
+	    !logging_active) {
+		struct hstate *h = hstate_vma(vma);
+
 		hugetlb = true;
-		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
+		gfn = (fault_ipa & huge_page_mask(h)) >> PAGE_SHIFT;
 	} else {
 		/*
 		 * Pages belonging to memslots that don't have the same

@@ -1521,15 +1544,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (mmu_notifier_retry(kvm, mmu_seq))
 		goto out_unlock;
 
-	if (!hugetlb && !force_pte) {
-		/*
-		 * Only PMD_SIZE transparent hugepages(THP) are
-		 * currently supported. This code will need to be
-		 * updated if other THP sizes are supported.
-		 */
+	if (!hugetlb && !force_pte)
 		hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
-		vma_pagesize = PMD_SIZE;

Why this change?  Won't you end up trying to map THPs as individual
pages now?

Argh - that's a rebase gone awry. Thanks for spotting.

There's another issue with this hunk - hugetlb can be false after the
call to transparent_hugepage_adjust(). I've fixed that up for the next
update.

quoted

-	}
 
 	if (writable)
 		kvm_set_pfn_dirty(pfn);

@@ -1540,7 +1556,23 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault)
 		invalidate_icache_guest_page(pfn, vma_pagesize);
 
-	if (hugetlb) {
+	if (vma_pagesize == PUD_SIZE) {
+		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
+
+		new_pud = kvm_pud_mkhuge(new_pud);
+		if (writable)
+			new_pud = kvm_s2pud_mkwrite(new_pud);
+
+		if (exec_fault) {
+			new_pud = kvm_s2pud_mkexec(new_pud);
+		} else if (fault_status == FSC_PERM) {
+			/* Preserve execute if XN was already cleared */
+			if (stage2_is_exec(kvm, fault_ipa))
+				new_pud = kvm_s2pud_mkexec(new_pud);
+		}

aha, another reason for my suggestion in the other patch.

Ack! Already fixed locally.

quoted

+
+		ret = stage2_set_pud_huge(kvm, memcache, fault_ipa, &new_pud);
+	} else if (vma_pagesize == PMD_SIZE) {
 		pmd_t new_pmd = kvm_pfn_pmd(pfn, mem_type);
 
 		new_pmd = kvm_pmd_mkhuge(new_pmd);
-- 
2.17.0

Otherwise, this patch looks fine.

Thanks a lot for reviewing the patches. I'll send out an update
incorporating your suggestions.

Punit