[PATCH 3/5] KVM: arm/arm64: Support dirty page tracking for contiguous hugepages

[Zenghui Yu]

When logging is enabled, we should keep tracking of normal size pages.
If the memslot is backed by contiguous hugepages, we should dissolve
the contiguous hugepages - clear the whole contiguous range and flush
corresponding TLB entry.

Move kvm_set_{pte,pmd} to the front of stage2_dissolve_cont_{pte,pmd}s
to avoid one more declaration.

Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
---
 arch/arm/include/asm/pgtable-hwdef.h |  8 ++++
 virt/kvm/arm/mmu.c                   | 76 ++++++++++++++++++++++++++++++------
 2 files changed, 72 insertions(+), 12 deletions(-)

diff --git a/arch/arm/include/asm/pgtable-hwdef.h b/arch/arm/include/asm/pgtable-hwdef.h
index 8426229..41f4633 100644
--- a/arch/arm/include/asm/pgtable-hwdef.h
+++ b/arch/arm/include/asm/pgtable-hwdef.h
@@ -16,4 +16,12 @@
 #include <asm/pgtable-2level-hwdef.h>
 #endif
 
+/* dummy definition */
+#define CONT_PTES		(0)
+#define CONT_PTE_SIZE		(0)
+#define CONT_PTE_MASK		(0)
+#define CONT_PMDS		(0)
+#define CONT_PMD_SIZE		(0)
+#define CONT_PMD_MASK		(0)
+
 #endif
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index cf8b035..36c863f 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -96,6 +96,58 @@ static bool kvm_is_device_pfn(unsigned long pfn)
 	return !pfn_valid(pfn);
 }
 
+static inline void kvm_set_pte(pte_t *ptep, pte_t new_pte)
+{
+	WRITE_ONCE(*ptep, new_pte);
+	dsb(ishst);
+}
+
+static inline void kvm_set_pmd(pmd_t *pmdp, pmd_t new_pmd)
+{
+	WRITE_ONCE(*pmdp, new_pmd);
+	dsb(ishst);
+}
+
+static void stage2_dissolve_cont_ptes(struct kvm *kvm, phys_addr_t addr,
+				      pte_t *pte)
+{
+	phys_addr_t addrp;
+	pte_t *ptep;
+	int i;
+
+	if (!kvm_s2pte_cont(*pte))
+		return;
+
+	/* Start with the first pte */
+	addrp = addr & CONT_PTE_MASK;
+	ptep = pte - (addr - addrp) / PAGE_SIZE;
+
+	for (i = 0; i < CONT_PTES; i++, ptep++, addrp += PAGE_SIZE) {
+		kvm_set_pte(ptep, __pte(0));
+		kvm_tlb_flush_vmid_ipa(kvm, addrp);
+		put_page(virt_to_page(ptep));
+	}
+}
+
+static void stage2_dissolve_cont_pmds(struct kvm *kvm, phys_addr_t addr,
+				      pmd_t *pmd)
+{
+	phys_addr_t addrp;
+	pmd_t *pmdp;
+	int i;
+
+	/* Start with the first pmd */
+	addr &= PMD_MASK;
+	addrp = addr & CONT_PMD_MASK;
+	pmdp = pmd - (addr - addrp) / PMD_SIZE;
+
+	for (i = 0; i < CONT_PMDS; i++, pmdp++, addrp += PMD_SIZE) {
+		pmd_clear(pmdp);
+		kvm_tlb_flush_vmid_ipa(kvm, addrp);
+		put_page(virt_to_page(pmdp));
+	}
+}
+
 /**
  * stage2_dissolve_pmd() - clear and flush huge PMD entry
  * @kvm:	pointer to kvm structure.
@@ -109,6 +161,11 @@ static void stage2_dissolve_pmd(struct kvm *kvm, phys_addr_t addr, pmd_t *pmd)
 	if (!pmd_thp_or_huge(*pmd))
 		return;
 
+	if (kvm_s2pmd_cont(*pmd)) {
+		stage2_dissolve_cont_pmds(kvm, addr, pmd);
+		return;
+	}
+
 	pmd_clear(pmd);
 	kvm_tlb_flush_vmid_ipa(kvm, addr);
 	put_page(virt_to_page(pmd));
@@ -193,18 +250,6 @@ static void clear_stage2_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr
 	put_page(virt_to_page(pmd));
 }
 
-static inline void kvm_set_pte(pte_t *ptep, pte_t new_pte)
-{
-	WRITE_ONCE(*ptep, new_pte);
-	dsb(ishst);
-}
-
-static inline void kvm_set_pmd(pmd_t *pmdp, pmd_t new_pmd)
-{
-	WRITE_ONCE(*pmdp, new_pmd);
-	dsb(ishst);
-}
-
 static inline void kvm_pmd_populate(pmd_t *pmdp, pte_t *ptep)
 {
 	kvm_set_pmd(pmdp, kvm_mk_pmd(ptep));
@@ -1289,6 +1334,13 @@ static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
 
 	pte = pte_offset_kernel(pmd, addr);
 
+	/*
+	 * While dirty page logging - dissolve contiguous PTE pages, then
+	 * continue on to allocate page.
+	 */
+	if (logging_active)
+		stage2_dissolve_cont_ptes(kvm, addr, pte);
+
 	if (iomap && pte_present(*pte))
 		return -EFAULT;
 
-- 
1.8.3.1