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

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Date:   Wed, 1 May 2019 09:44:25 +0000
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>
CC:     <marc.zyngier@....com>, <christoffer.dall@....com>,
        <linux@...linux.org.uk>, <catalin.marinas@....com>,
        <will.deacon@....com>, <james.morse@....com>,
        <julien.thierry@....com>, <suzuki.poulose@....com>,
        <steve.capper@....com>, <wanghaibin.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>
Subject: [PATCH 3/5] KVM: arm/arm64: Support dirty page tracking for contiguous hugepages

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@...wei.com>
---
 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