[PATCH 5/8] KVM: arm64: get dirty pages from the page tracking device

Lilit Janpoladyan
2024-09-18T15:28:25Z

If a page tracking device is available, use it in
kvm_arch_sync_dirty_log to read device dirty log and mark logged
pages as dirty. Allocate a page to use as a buffer for reading
device dirty log; the allocation and access to the page are not
synchronized - assumes that userspace won't try to enable/disable
dirty logging and read dirty log at the same time.

Signed-off-by: Lilit Janpoladyan <lilitj@amazon.com>
---
arch/arm64/include/asm/kvm_host.h | 3 +-
arch/arm64/kvm/arm.c | 46 ++++++++++++++++++++++++++++++-
2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index db9bf42123e1..a76f25d4d2bc 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -379,9 +379,10 @@ struct kvm_arch {
struct kvm_protected_vm pkvm;

/*
- * Stores page tracking context if page tracking device is in use
+ * Stores page tracking context and buffer if page tracking device is in use
*/
void *page_tracking_ctx;
+ gpa_t *page_tracking_pg;
};

struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index c8dcf719ee99..139d7e929266 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1822,6 +1822,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
int kvm_arch_enable_dirty_logging(struct kvm *kvm, const struct kvm_memory_slot *memslot)
{
void *ctx = NULL;
+ unsigned long read_buffer;
struct pt_config config;
int r;

@@ -1836,16 +1837,31 @@ int kvm_arch_enable_dirty_logging(struct kvm *kvm, const struct kvm_memory_slot
return -ENOENT;

kvm->arch.page_tracking_ctx = ctx;
+
+ read_buffer = __get_free_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+ if (!read_buffer) {
+ r = -ENOMEM;
+ goto out_free;
+ }
+
+ kvm->arch.page_tracking_pg = (gpa_t *)read_buffer;
}

r = page_tracking_enable(kvm->arch.page_tracking_ctx, -1);

+out_free:
if (r) {
if (ctx) {
page_tracking_release(ctx);
kvm->arch.page_tracking_ctx = NULL;
}
+
+ if (read_buffer) {
+ free_page(read_buffer);
+ kvm->arch.page_tracking_pg = NULL;
+ }
}
+
return r;
}

@@ -1866,13 +1882,41 @@ int kvm_arch_disable_dirty_logging(struct kvm *kvm, const struct kvm_memory_slot
} else {
page_tracking_release(kvm->arch.page_tracking_ctx);
kvm->arch.page_tracking_ctx = NULL;
+
+ if (kvm->arch.page_tracking_pg) {
+ free_page((unsigned long)kvm->arch.page_tracking_pg);
+ kvm->arch.page_tracking_pg = NULL;
+ }
}
return r;
}

-void kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
+int kvm_arch_sync_dirty_log(struct kvm *kvm, struct kvm_memory_slot *memslot)
{
+ int r;
+ u32 i;
+ u32 max_pages = PAGE_SIZE/sizeof(gpa_t);

+ if (!kvm->arch.page_tracking_ctx)
+ return 0;
+
+ if (!kvm->arch.page_tracking_pg)
+ return -ENOENT;
+
+ r = page_tracking_read_dirty_pages(kvm->arch.page_tracking_ctx, -1,
+ kvm->arch.page_tracking_pg, max_pages);
+
+ while (r > 0) {
+ for (i = 0; i < r; ++i) {
+ u32 gfn = kvm->arch.page_tracking_pg[i] >> PAGE_SHIFT;
+
+ memslot = gfn_to_memslot(kvm, gfn);
+ mark_page_dirty_in_slot(kvm, memslot, gfn);
+ }
+ r = page_tracking_read_dirty_pages(kvm->arch.page_tracking_ctx, -1,
+ kvm->arch.page_tracking_pg, max_pages);
+ }
+ return r < 0 ? r : 0;
}

static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
--
2.40.1