[PATCH v4 03/10] KVM: arm64: Invoke the snapshot interface for the host stage-2 pagetable

[Sebastian Ene]

Allocate memory for the snapshot by creating a memory cache with empty
pages that will be used by the hypervisor during the page table copy.
Get the required size of the PGD and allocate physically contiguous
memory for it. Allocate contiguous memory for an array that is used to
keep track of the pages used from the memcache. Call the snapshot
interface and release the memory for the snapshot.

Signed-off-by: Sebastian Ene <sebastianene at google.com>
---
 arch/arm64/kvm/ptdump.c | 107 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)

diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index 5816fc632..e99bab427 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -25,6 +25,9 @@ static int kvm_ptdump_open(struct inode *inode, struct file *file);
 static int kvm_ptdump_release(struct inode *inode, struct file *file);
 static int kvm_ptdump_show(struct seq_file *m, void *);
 
+static phys_addr_t get_host_pa(void *addr);
+static void *get_host_va(phys_addr_t pa);
+
 static const struct file_operations kvm_ptdump_fops = {
 	.open		= kvm_ptdump_open,
 	.read		= seq_read,
@@ -32,6 +35,11 @@ static const struct file_operations kvm_ptdump_fops = {
 	.release	= kvm_ptdump_release,
 };
 
+static struct kvm_pgtable_mm_ops ptdump_host_mmops = {
+	.phys_to_virt	= get_host_va,
+	.virt_to_phys	= get_host_pa,
+};
+
 static int kvm_ptdump_open(struct inode *inode, struct file *file)
 {
 	struct kvm_ptdump_register *reg = inode->i_private;
@@ -78,11 +86,110 @@ static void kvm_ptdump_debugfs_register(struct kvm_ptdump_register *reg,
 
 static struct kvm_ptdump_register host_reg;
 
+static size_t host_stage2_get_pgd_len(void)
+{
+	u32 phys_shift = get_kvm_ipa_limit();
+	u64 vtcr = kvm_get_vtcr(read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1),
+				read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1),
+				phys_shift);
+	return (kvm_pgtable_stage2_pgd_size(vtcr) >> PAGE_SHIFT);
+}
+
+static phys_addr_t get_host_pa(void *addr)
+{
+	return __pa(addr);
+}
+
+static void *get_host_va(phys_addr_t pa)
+{
+	return __va(pa);
+}
+
+static void kvm_host_put_ptdump_info(void *snap)
+{
+	void *mc_page;
+	size_t i;
+	struct kvm_pgtable_snapshot *snapshot;
+
+	if (!snap)
+		return;
+
+	snapshot = snap;
+	while ((mc_page = pop_hyp_memcache(&snapshot->mc, get_host_va)) != NULL)
+		free_page((unsigned long)mc_page);
+
+	if (snapshot->pgd_hva)
+		free_pages_exact(snapshot->pgd_hva, snapshot->pgd_pages);
+
+	if (snapshot->used_pages_hva) {
+		for (i = 0; i < snapshot->used_pages_indx; i++) {
+			mc_page = get_host_va(snapshot->used_pages_hva[i]);
+			free_page((unsigned long)mc_page);
+		}
+
+		free_pages_exact(snapshot->used_pages_hva, snapshot->num_used_pages);
+	}
+
+	free_page((unsigned long)snapshot);
+}
+
+static void *kvm_host_get_ptdump_info(struct kvm_ptdump_register *reg)
+{
+	int i, ret;
+	void *mc_page;
+	struct kvm_pgtable_snapshot *snapshot;
+	size_t memcache_len;
+
+	snapshot = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
+	if (!snapshot)
+		return NULL;
+
+	memset(snapshot, 0, sizeof(struct kvm_pgtable_snapshot));
+
+	snapshot->pgd_pages = host_stage2_get_pgd_len();
+	snapshot->pgd_hva = alloc_pages_exact(snapshot->pgd_pages, GFP_KERNEL_ACCOUNT);
+	if (!snapshot->pgd_hva)
+		goto err;
+
+	memcache_len = (size_t)reg->priv;
+	for (i = 0; i < memcache_len; i++) {
+		mc_page = (void *)__get_free_page(GFP_KERNEL_ACCOUNT);
+		if (!mc_page)
+			goto err;
+
+		push_hyp_memcache(&snapshot->mc, mc_page, get_host_pa);
+	}
+
+	snapshot->num_used_pages = DIV_ROUND_UP(sizeof(phys_addr_t) * memcache_len,
+					     PAGE_SIZE);
+	snapshot->used_pages_hva = alloc_pages_exact(snapshot->num_used_pages,
+						  GFP_KERNEL_ACCOUNT);
+	if (!snapshot->used_pages_hva)
+		goto err;
+
+	ret = kvm_call_hyp_nvhe(__pkvm_host_stage2_snapshot, snapshot);
+	if (ret) {
+		pr_err("ERROR %d snapshot host pagetables\n", ret);
+		goto err;
+	}
+
+	snapshot->pgtable.pgd = get_host_va((phys_addr_t)snapshot->pgtable.pgd);
+	snapshot->pgtable.mm_ops = &ptdump_host_mmops;
+
+	return snapshot;
+err:
+	kvm_host_put_ptdump_info(snapshot);
+	return NULL;
+}
+
 void kvm_ptdump_register_host(void)
 {
 	if (!is_protected_kvm_enabled())
 		return;
 
+	host_reg.get_ptdump_info = kvm_host_get_ptdump_info;
+	host_reg.put_ptdump_info = kvm_host_put_ptdump_info;
+
 	kvm_ptdump_debugfs_register(&host_reg, "host_page_tables",
 				    kvm_debugfs_dir);
 }
-- 
2.43.0.472.g3155946c3a-goog