[PATCH v3 6/9] KVM: arm64: selftests: shadow_stage2: Allocate L2 stack from dedicated pool

[Wei-Lin Chang]

Instead of using L1's stack, create a simple page allocator and use that
to allocate L2 stack. The allocator will also be used later on when the
stage-2 page table generator builds stage-2 mappings for the nested
guest (L2).

Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
 .../selftests/kvm/arm64/shadow_stage2.c       | 20 ++++++++---
 .../selftests/kvm/include/arm64/nested.h      |  9 +++++
 .../testing/selftests/kvm/lib/arm64/nested.c  | 33 +++++++++++++++++++
 3 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/shadow_stage2.c b/tools/testing/selftests/kvm/arm64/shadow_stage2.c
index cf76a2b0582d..1ad510a38654 100644
--- a/tools/testing/selftests/kvm/arm64/shadow_stage2.c
+++ b/tools/testing/selftests/kvm/arm64/shadow_stage2.c
@@ -9,12 +9,16 @@
 #include "ucall.h"
 
 #define XLATE2GPA	(0xABCD)
-#define L2STACKSZ	(0x100)
 
 #define L2SUCCESS	(0x0)
 #define L2FAILED	(0x1)
 #define L2SYNC		(0x2)
 
+/* Used for L2 stack and guest S2 page tables. */
+#define L2_PAGE_POOL_ADDR	(0x80000000)
+#define L2_PAGE_POOL_NPAGES	(512)
+#define L2_PAGE_POOL_MEMSLOT	(0x2)
+
 /*
  * TPIDR_EL2 is used to store vcpu id, so save and restore it.
  */
@@ -48,14 +52,18 @@ static void guest_code(void)
 	struct hyp_data hyp_data;
 	int ret, i = 0;
 	gpa_t l2_pc, l2_stack_top;
-	/* force 16-byte alignment for the stack pointer */
-	u8 l2_stack[L2STACKSZ] __attribute__((aligned(16)));
+	struct page_pool pp;
 
 	GUEST_ASSERT_EQ(get_current_el(), 2);
 	GUEST_PRINTF("vEL2 entry\n");
 
+	pp.start = L2_PAGE_POOL_ADDR;
+	pp.npages = L2_PAGE_POOL_NPAGES;
+	pp.current = L2_PAGE_POOL_ADDR;
+	pp.page_size = get_page_size();
+
+	l2_stack_top = alloc_page(&pp) + pp.page_size;
 	l2_pc = ucall_translate_to_gpa(l2_guest_code);
-	l2_stack_top = ucall_translate_to_gpa(&l2_stack[L2STACKSZ]);
 
 	init_vcpu(&vcpu, l2_pc, l2_stack_top);
 	prepare_hyp();
@@ -96,6 +104,10 @@ int main(void)
 	vcpu = aarch64_vcpu_add(vm, 0, &init, guest_code);
 	kvm_arch_vm_finalize_vcpus(vm);
 
+	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+				    L2_PAGE_POOL_ADDR, L2_PAGE_POOL_MEMSLOT,
+				    L2_PAGE_POOL_NPAGES, 0);
+
 	while (true) {
 		vcpu_run(vcpu);
 
diff --git a/tools/testing/selftests/kvm/include/arm64/nested.h b/tools/testing/selftests/kvm/include/arm64/nested.h
index c10ef4a85be7..8e7d7738b381 100644
--- a/tools/testing/selftests/kvm/include/arm64/nested.h
+++ b/tools/testing/selftests/kvm/include/arm64/nested.h
@@ -46,6 +46,15 @@ struct hyp_data {
 	struct cpu_context hyp_context;
 };
 
+struct page_pool {
+	gpa_t start;
+	gpa_t current;
+	size_t npages;
+	size_t page_size;
+};
+
+size_t get_page_size(void);
+gpa_t alloc_page(struct page_pool *pp);
 void prepare_hyp(void);
 void init_vcpu(struct vcpu *vcpu, gpa_t l2_pc, gpa_t l2_stack_top);
 int run_l2(struct vcpu *vcpu, struct hyp_data *hyp_data);
diff --git a/tools/testing/selftests/kvm/lib/arm64/nested.c b/tools/testing/selftests/kvm/lib/arm64/nested.c
index f6c24beb01d0..7f47e340f00d 100644
--- a/tools/testing/selftests/kvm/lib/arm64/nested.c
+++ b/tools/testing/selftests/kvm/lib/arm64/nested.c
@@ -7,6 +7,39 @@
 #include "processor.h"
 #include "test_util.h"
 #include <asm/sysreg.h>
+#include <linux/sizes.h>
+
+size_t get_page_size(void)
+{
+	u64 tcr_el1 = read_sysreg(tcr_el1);
+	u64 tg0 = SYS_FIELD_GET(TCR_EL1, TG0, tcr_el1);
+
+	switch (tg0) {
+	case TCR_EL1_TG0_4K:
+		return SZ_4K;
+	case TCR_EL1_TG0_16K:
+		return SZ_16K;
+	case TCR_EL1_TG0_64K:
+		return SZ_64K;
+	default:
+		GUEST_FAIL("Unexpected tg0 value!\n");
+		return 0;
+	}
+}
+
+gpa_t alloc_page(struct page_pool *pp)
+{
+	gpa_t page = pp->current;
+
+	pp->current += pp->page_size;
+
+	if ((pp->current - pp->start) / pp->page_size <= pp->npages) {
+		return page;
+	} else {
+		GUEST_FAIL("%s failed!\n", __func__);
+		return 0;
+	}
+}
 
 void prepare_hyp(void)
 {
-- 
2.43.0