Subject: [PATCH 0521/2944] KVM: arm64: Support dirty page tracking for PUD hugepages

From: Punit Agrawal <[email-masked]>
Date: Tue, 11 Dec 2018 17:10:37 +0000

commit 4ea5af53114091e23a8fc279f25637e6c4e892c6 upstream.

In preparation for creating PUD hugepages at stage 2, add support for
write protecting PUD hugepages when they are encountered. Write
protecting guest tables is used to track dirty pages when migrating
VMs.

Also, provide trivial implementations of required kvm_s2pud_* helpers
to allow sharing of code with arm32.

Signed-off-by: Punit Agrawal <[email-masked]>
Reviewed-by: Christoffer Dall <[email-masked]>
Cc: Russell King <[email-masked]>
Cc: Catalin Marinas <[email-masked]>
Cc: Will Deacon <[email-masked]>
[ Replaced BUG() => WARN_ON() in arm32 pud helpers ]
Signed-off-by: Suzuki K Poulose <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
Signed-off-by: Shannon Zhao <[email-masked]>
Acked-by: Zou Cao <[email-masked]>
---
 arch/arm/include/asm/kvm_mmu.h   | 15 +++++++++++++++
 arch/arm64/include/asm/kvm_mmu.h | 10 ++++++++++
 virt/kvm/arm/mmu.c               | 11 +++++++----
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index c1961c1..85c21b9 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -84,6 +84,21 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
 
 #define kvm_pmd_mkhuge(pmd)	pmd_mkhuge(pmd)
 
+/*
+ * The following kvm_*pud*() functions are provided strictly to allow
+ * sharing code with arm64. They should never be called in practice.
+ */
+static inline void kvm_set_s2pud_readonly(pud_t *pud)
+{
+	WARN_ON(1);
+}
+
+static inline bool kvm_s2pud_readonly(pud_t *pud)
+{
+	WARN_ON(1);
+	return false;
+}
+
 static inline pte_t kvm_s2pte_mkwrite(pte_t pte)
 {
 	pte_val(pte) |= L_PTE_S2_RDWR;
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index ed23f34..4aea387 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -249,6 +249,16 @@ static inline bool kvm_page_empty(void *ptr)
 	return page_count(ptr_page) == 1;
 }
 
+static inline void kvm_set_s2pud_readonly(pud_t *pudp)
+{
+	kvm_set_s2pte_readonly((pte_t *)pudp);
+}
+
+static inline bool kvm_s2pud_readonly(pud_t *pudp)
+{
+	return kvm_s2pte_readonly((pte_t *)pudp);
+}
+
 #define hyp_pte_table_empty(ptep) kvm_page_empty(ptep)
 
 #ifdef __PAGETABLE_PMD_FOLDED
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index c3a505a..8e03732 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1344,9 +1344,12 @@ static void  stage2_wp_puds(pgd_t *pgd, phys_addr_t addr, phys_addr_t end)
 	do {
 		next = stage2_pud_addr_end(addr, end);
 		if (!stage2_pud_none(*pud)) {
-			/* TODO:PUD not supported, revisit later if supported */
-			BUG_ON(stage2_pud_huge(*pud));
-			stage2_wp_pmds(pud, addr, next);
+			if (stage2_pud_huge(*pud)) {
+				if (!kvm_s2pud_readonly(pud))
+					kvm_set_s2pud_readonly(pud);
+			} else {
+				stage2_wp_pmds(pud, addr, next);
+			}
 		}
 	} while (pud++, addr = next, addr != end);
 }
@@ -1389,7 +1392,7 @@ static void stage2_wp_range(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
  *
  * Called to start logging dirty pages after memory region
  * KVM_MEM_LOG_DIRTY_PAGES operation is called. After this function returns
- * all present PMD and PTEs are write protected in the memory region.
+ * all present PUD, PMD and PTEs are write protected in the memory region.
  * Afterwards read of dirty page log can be called.
  *
  * Acquires kvm_mmu_lock. Called with kvm->slots_lock mutex acquired,
-- 
1.8.3.1