[PATCH v9 2/4] arm: ARMv7 dirty page logging inital mem region write protect (w/no huge PUD support)

Mario Smarduch
2014-07-25T00:56:16Z

Patch adds support for initial write protection VM memlsot. This patch series
assumes that huge PUDs will not be used in 2nd stage tables.

Signed-off-by: Mario Smarduch <m.smarduch@samsung.com>
---
arch/arm/include/asm/kvm_host.h | 1 +
arch/arm/include/asm/kvm_mmu.h | 20 ++++++
arch/arm/include/asm/pgtable-3level.h | 1 +
arch/arm/kvm/arm.c | 9 +++
arch/arm/kvm/mmu.c | 128 +++++++++++++++++++++++++++++++++
5 files changed, 159 insertions(+)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 042206f..6521a2d 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -231,5 +231,6 @@ int kvm_perf_teardown(void);
u64 kvm_arm_timer_get_reg(struct kvm_vcpu *, u64 regid);
int kvm_arm_timer_set_reg(struct kvm_vcpu *, u64 regid, u64 value);
void kvm_arch_flush_remote_tlbs(struct kvm *);
+void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);

#endif /* __ARM_KVM_HOST_H__ */
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 5cc0b0f..08ab5e8 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -114,6 +114,26 @@ static inline void kvm_set_s2pmd_writable(pmd_t *pmd)
pmd_val(*pmd) |= L_PMD_S2_RDWR;
}

+static inline void kvm_set_s2pte_readonly(pte_t *pte)
+{
+ pte_val(*pte) = (pte_val(*pte) & ~L_PTE_S2_RDWR) | L_PTE_S2_RDONLY;
+}
+
+static inline bool kvm_s2pte_readonly(pte_t *pte)
+{
+ return (pte_val(*pte) & L_PTE_S2_RDWR) == L_PTE_S2_RDONLY;
+}
+
+static inline void kvm_set_s2pmd_readonly(pmd_t *pmd)
+{
+ pmd_val(*pmd) = (pmd_val(*pmd) & ~L_PMD_S2_RDWR) | L_PMD_S2_RDONLY;
+}
+
+static inline bool kvm_s2pmd_readonly(pmd_t *pmd)
+{
+ return (pmd_val(*pmd) & L_PMD_S2_RDWR) == L_PMD_S2_RDONLY;
+}
+
/* Open coded p*d_addr_end that can deal with 64bit addresses */
#define kvm_pgd_addr_end(addr, end) \
({ u64 __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK; \
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index 85c60ad..d8bb40b 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -129,6 +129,7 @@
#define L_PTE_S2_RDONLY (_AT(pteval_t, 1) << 6) /* HAP[1] */
#define L_PTE_S2_RDWR (_AT(pteval_t, 3) << 6) /* HAP[2:1] */

+#define L_PMD_S2_RDONLY (_AT(pteval_t, 1) << 6) /* HAP[1] */
#define L_PMD_S2_RDWR (_AT(pmdval_t, 3) << 6) /* HAP[2:1] */

/*
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 3c82b37..e11c2dd 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -242,6 +242,15 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
const struct kvm_memory_slot *old,
enum kvm_mr_change change)
{
+#ifdef CONFIG_ARM
+ /*
+ * At this point memslot has been committed and there is an
+ * allocated dirty_bitmap[], dirty pages will be be tracked while the
+ * memory slot is write protected.
+ */
+ if ((change != KVM_MR_DELETE) && (mem->flags & KVM_MEM_LOG_DIRTY_PAGES))
+ kvm_mmu_wp_memory_region(kvm, mem->slot);
+#endif
}

void kvm_arch_flush_shadow_all(struct kvm *kvm)
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 35254c6..7bfc792 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -763,6 +763,134 @@ static bool transparent_hugepage_adjust(pfn_t *pfnp, phys_addr_t *ipap)
return false;
}

+#ifdef CONFIG_ARM
+/**
+ * stage2_wp_pte_range - write protect PTE range
+ * @pmd: pointer to pmd entry
+ * @addr: range start address
+ * @end: range end address
+ */
+static void stage2_wp_pte_range(pmd_t *pmd, phys_addr_t addr, phys_addr_t end)
+{
+ pte_t *pte;
+
+ pte = pte_offset_kernel(pmd, addr);
+ do {
+ if (!pte_none(*pte)) {
+ if (!kvm_s2pte_readonly(pte))
+ kvm_set_s2pte_readonly(pte);
+ }
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+}
+
+/**
+ * stage2_wp_pmd_range - write protect PMD range
+ * @pud: pointer to pud entry
+ * @addr: range start address
+ * @end: range end address
+ */
+static void stage2_wp_pmd_range(pud_t *pud, phys_addr_t addr, phys_addr_t end)
+{
+ pmd_t *pmd;
+ phys_addr_t next;
+
+ pmd = pmd_offset(pud, addr);
+
+ do {
+ next = kvm_pmd_addr_end(addr, end);
+ if (!pmd_none(*pmd)) {
+ if (kvm_pmd_huge(*pmd)) {
+ if (!kvm_s2pmd_readonly(pmd))
+ kvm_set_s2pmd_readonly(pmd);
+ } else
+ stage2_wp_pte_range(pmd, addr, next);
+
+ }
+ } while (pmd++, addr = next, addr != end);
+}
+
+/**
+ * stage2_wp_pud_range - write protect PUD range
+ * @kvm: pointer to kvm structure
+ * @pud: pointer to pgd entry
+ * @addr: range start address
+ * @end: range end address
+ *
+ * While walking the PUD range huge PUD pages are ignored, in the future this
+ * may need to be revisited. Determine how to handle huge PUDs when logging
+ * of dirty pages is enabled.
+ */
+static void stage2_wp_pud_range(struct kvm *kvm, pgd_t *pgd,
+ phys_addr_t addr, phys_addr_t end)
+{
+ pud_t *pud;
+ phys_addr_t next;
+
+ pud = pud_offset(pgd, addr);
+ do {
+ next = kvm_pud_addr_end(addr, end);
+ /* TODO: huge PUD not supported, revisit later */
+ BUG_ON(pud_huge(*pud));
+ if (!pud_none(*pud))
+ stage2_wp_pmd_range(pud, addr, next);
+ } while (pud++, addr = next, addr != end);
+}
+
+/**
+ * stage2_wp_range() - write protect stage2 memory region range
+ * @kvm: The KVM pointer
+ * @start: Start address of range
+ * &end: End address of range
+ */
+static void stage2_wp_range(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
+{
+ pgd_t *pgd;
+ phys_addr_t next;
+
+ pgd = kvm->arch.pgd + pgd_index(addr);
+ do {
+ /*
+ * Release kvm_mmu_lock periodically if the memory region is
+ * large features like detect hung task, lock detector or lock
+ * dep may panic. In addition holding the lock this long will
+ * also starve other vCPUs. Applies to huge VM memory regions.
+ */
+ if (need_resched() || spin_needbreak(&kvm->mmu_lock))
+ cond_resched_lock(&kvm->mmu_lock);
+
+ next = kvm_pgd_addr_end(addr, end);
+ if (pgd_present(*pgd))
+ stage2_wp_pud_range(kvm, pgd, addr, next);
+ } while (pgd++, addr = next, addr != end);
+}
+
+/**
+ * kvm_mmu_wp_memory_region() - write protect stage 2 entries for memory slot
+ * @kvm: The KVM pointer
+ * @slot: The memory slot to write protect
+ *
+ * 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.
+ * Afterwards read of dirty page log can be called.
+ *
+ * Acquires kvm_mmu_lock. Called with kvm->slots_lock mutex acquired,
+ * serializing operations for VM memory regions.
+ */
+
+void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
+{
+ struct kvm_memory_slot *memslot = id_to_memslot(kvm->memslots, slot);
+ phys_addr_t start = memslot->base_gfn << PAGE_SHIFT;
+ phys_addr_t end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT;
+
+ spin_lock(&kvm->mmu_lock);
+ stage2_wp_range(kvm, start, end);
+ kvm_flush_remote_tlbs(kvm);
+ spin_unlock(&kvm->mmu_lock);
+}
+#endif
+
static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
struct kvm_memory_slot *memslot,
unsigned long fault_status)
--
1.7.9.5