[PATCH 3/3] KVM: arm64: selftests: Enable stage-2 in NV preparation functions
Wei-Lin Chang
weilin.chang at arm.com
Tue Mar 24 17:36:20 PDT 2026
Introduce library functions for setting up guest stage-2 page tables,
then use that to give L2 an identity mapped stage-2 and enable it.
The translation and stage-2 page table built is simple, start level 0,
4 levels, 4KB granules, normal cachable, 48-bit IA, 40-bit OA.
The nested page table code is adapted from lib/x86/vmx.c.
Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
.../selftests/kvm/include/arm64/nested.h | 7 ++
.../selftests/kvm/include/arm64/processor.h | 9 ++
.../testing/selftests/kvm/lib/arm64/nested.c | 97 ++++++++++++++++++-
3 files changed, 111 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/arm64/nested.h b/tools/testing/selftests/kvm/include/arm64/nested.h
index 739ff2ee0161..0be10a775e48 100644
--- a/tools/testing/selftests/kvm/include/arm64/nested.h
+++ b/tools/testing/selftests/kvm/include/arm64/nested.h
@@ -6,6 +6,13 @@
#ifndef SELFTEST_KVM_NESTED_H
#define SELFTEST_KVM_NESTED_H
+uint64_t get_l1_vtcr(void);
+
+void nested_map(struct kvm_vm *vm, vm_paddr_t guest_pgd,
+ uint64_t nested_paddr, uint64_t paddr, uint64_t size);
+void nested_map_memslot(struct kvm_vm *vm, vm_paddr_t guest_pgd,
+ uint32_t memslot);
+
void prepare_l2_stack(struct kvm_vm *vm, struct kvm_vcpu *vcpu);
void prepare_hyp_state(struct kvm_vm *vm, struct kvm_vcpu *vcpu);
void prepare_eret_destination(struct kvm_vm *vm, struct kvm_vcpu *vcpu, void *l2_pc);
diff --git a/tools/testing/selftests/kvm/include/arm64/processor.h b/tools/testing/selftests/kvm/include/arm64/processor.h
index ac97a1c436fc..5de2e932d95a 100644
--- a/tools/testing/selftests/kvm/include/arm64/processor.h
+++ b/tools/testing/selftests/kvm/include/arm64/processor.h
@@ -104,6 +104,15 @@
#define TCR_HA (UL(1) << 39)
#define TCR_DS (UL(1) << 59)
+/* VTCR_EL2 specific flags */
+#define VTCR_EL2_T0SZ_BITS(x) ((UL(64) - (x)) << VTCR_EL2_T0SZ_SHIFT)
+
+#define VTCR_EL2_SL0_LV0_4K (UL(2) << VTCR_EL2_SL0_SHIFT)
+#define VTCR_EL2_SL0_LV1_4K (UL(1) << VTCR_EL2_SL0_SHIFT)
+#define VTCR_EL2_SL0_LV2_4K (UL(0) << VTCR_EL2_SL0_SHIFT)
+
+#define VTCR_EL2_PS_40_BITS (UL(2) << VTCR_EL2_PS_SHIFT)
+
/*
* AttrIndx[2:0] encoding (mapping attributes defined in the MAIR* registers).
*/
diff --git a/tools/testing/selftests/kvm/lib/arm64/nested.c b/tools/testing/selftests/kvm/lib/arm64/nested.c
index 111d02f44cfe..910f8cd30f96 100644
--- a/tools/testing/selftests/kvm/lib/arm64/nested.c
+++ b/tools/testing/selftests/kvm/lib/arm64/nested.c
@@ -1,8 +1,11 @@
// SPDX-License-Identifier: GPL-2.0
/*
- * ARM64 Nested virtualization helpers
+ * ARM64 Nested virtualization helpers, nested page table code adapted from
+ * ../x86/vmx.c.
*/
+#include <linux/sizes.h>
+
#include "kvm_util.h"
#include "nested.h"
#include "processor.h"
@@ -18,6 +21,87 @@ static void hvc_handler(struct ex_regs *regs)
regs->pc = (u64)after_hvc;
}
+uint64_t get_l1_vtcr(void)
+{
+ return VTCR_EL2_PS_40_BITS | VTCR_EL2_TG0_4K | VTCR_EL2_ORGN0_WBWA |
+ VTCR_EL2_IRGN0_WBWA | VTCR_EL2_SL0_LV0_4K | VTCR_EL2_T0SZ_BITS(48);
+}
+
+static void __nested_pg_map(struct kvm_vm *vm, uint64_t guest_pgd,
+ uint64_t nested_paddr, uint64_t paddr, uint64_t flags)
+{
+ uint8_t attr_idx = flags & (PTE_ATTRINDX_MASK >> PTE_ATTRINDX_SHIFT);
+ uint64_t pg_attr;
+ uint64_t *ptep;
+
+ TEST_ASSERT((nested_paddr % vm->page_size) == 0,
+ "L2 IPA not on page boundary,\n"
+ " nested_paddr: 0x%lx vm->page_size: 0x%x", nested_paddr, vm->page_size);
+ TEST_ASSERT((paddr % vm->page_size) == 0,
+ "Guest physical address not on page boundary,\n"
+ " paddr: 0x%lx vm->page_size: 0x%x", paddr, vm->page_size);
+ TEST_ASSERT((paddr >> vm->page_shift) <= vm->max_gfn,
+ "Physical address beyond maximum supported,\n"
+ " paddr: 0x%lx vm->max_gfn: 0x%lx vm->page_size: 0x%x",
+ paddr, vm->max_gfn, vm->page_size);
+
+ ptep = addr_gpa2hva(vm, guest_pgd) + ((nested_paddr >> 39) & 0x1ffu) * 8;
+ if (!*ptep)
+ *ptep = (vm_alloc_page_table(vm) & GENMASK(47, 12)) | PGD_TYPE_TABLE | PTE_VALID;
+ ptep = addr_gpa2hva(vm, *ptep & GENMASK(47, 12)) + ((nested_paddr >> 30) & 0x1ffu) * 8;
+ if (!*ptep)
+ *ptep = (vm_alloc_page_table(vm) & GENMASK(47, 12)) | PUD_TYPE_TABLE | PTE_VALID;
+ ptep = addr_gpa2hva(vm, *ptep & GENMASK(47, 12)) + ((nested_paddr >> 21) & 0x1ffu) * 8;
+ if (!*ptep)
+ *ptep = (vm_alloc_page_table(vm) & GENMASK(47, 12)) | PMD_TYPE_TABLE | PTE_VALID;
+ ptep = addr_gpa2hva(vm, *ptep & GENMASK(47, 12)) + ((nested_paddr >> 12) & 0x1ffu) * 8;
+
+ pg_attr = PTE_AF | PTE_ATTRINDX(attr_idx) | PTE_TYPE_PAGE | PTE_VALID;
+ pg_attr |= PTE_SHARED;
+
+ *ptep = (paddr & GENMASK(47, 12)) | pg_attr;
+}
+
+void nested_map(struct kvm_vm *vm, vm_paddr_t guest_pgd,
+ uint64_t nested_paddr, uint64_t paddr, uint64_t size)
+{
+ size_t npages = size / SZ_4K;
+
+ TEST_ASSERT(nested_paddr + size > nested_paddr, "Vaddr overflow");
+ TEST_ASSERT(paddr + size > paddr, "Paddr overflow");
+
+ while (npages--) {
+ __nested_pg_map(vm, guest_pgd, nested_paddr, paddr, MT_NORMAL);
+ nested_paddr += SZ_4K;
+ paddr += SZ_4K;
+ }
+}
+
+/*
+ * Prepare an identity shadow page table that maps all the
+ * physical pages in VM.
+ */
+void nested_map_memslot(struct kvm_vm *vm, vm_paddr_t guest_pgd,
+ uint32_t memslot)
+{
+ sparsebit_idx_t i, last;
+ struct userspace_mem_region *region =
+ memslot2region(vm, memslot);
+
+ i = (region->region.guest_phys_addr >> vm->page_shift) - 1;
+ last = i + (region->region.memory_size >> vm->page_shift);
+ for (;;) {
+ i = sparsebit_next_clear(region->unused_phy_pages, i);
+ if (i > last)
+ break;
+
+ nested_map(vm, guest_pgd,
+ (uint64_t)i << vm->page_shift,
+ (uint64_t)i << vm->page_shift,
+ 1 << vm->page_shift);
+ }
+}
+
void prepare_l2_stack(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
{
size_t l2_stack_size;
@@ -32,7 +116,16 @@ void prepare_l2_stack(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
void prepare_hyp_state(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
{
- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_HCR_EL2), HCR_EL2_RW);
+ vm_paddr_t guest_pgd;
+
+ guest_pgd = vm_phy_pages_alloc(vm, 1,
+ KVM_GUEST_PAGE_TABLE_MIN_PADDR,
+ vm->memslots[MEM_REGION_PT]);
+ nested_map_memslot(vm, guest_pgd, 0);
+
+ vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_HCR_EL2), HCR_EL2_RW | HCR_EL2_VM);
+ vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_VTTBR_EL2), guest_pgd);
+ vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_VTCR_EL2), get_l1_vtcr());
}
void prepare_eret_destination(struct kvm_vm *vm, struct kvm_vcpu *vcpu, void *l2_pc)
--
2.43.0
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