[PATCH v2] KVM: selftests: x86: Prioritize getting max_gfn from GuestPhysBits

[Tao Su <tao1.su@linux.intel.com>]

Use the max mappable GPA via GuestPhysBits advertised by KVM to calculate
max_gfn. Currently some selftests (e.g. access_tracking_perf_test,
dirty_log_test...) add RAM regions close to max_gfn, so guest may access
GPA beyond its mappable range and cause infinite loop.

Adjust max_gfn in vm_compute_max_gfn() since x86 selftests already
overrides vm_compute_max_gfn() specifically to deal with goofy edge cases.

Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Tested-by: Yi Lai <yi1.lai@intel.com>
---
This patch is based on https://github.com/kvm-x86/linux/commit/b628cb523c65

Changelog:
v1 -> v2:
 - Only adjust vm->max_gfn in vm_compute_max_gfn()
 - Add Yi Lai's Tested-by

v1: https://lore.kernel.org/all/20240508064205.15301-1-tao1.su@linux.intel.com/
---
 tools/testing/selftests/kvm/include/x86_64/processor.h |  1 +
 tools/testing/selftests/kvm/lib/x86_64/processor.c     | 10 ++++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 81ce37ec407d..ff99f66d81a0 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -282,6 +282,7 @@ struct kvm_x86_cpu_property {
 #define X86_PROPERTY_MAX_EXT_LEAF		KVM_X86_CPU_PROPERTY(0x80000000, 0, EAX, 0, 31)
 #define X86_PROPERTY_MAX_PHY_ADDR		KVM_X86_CPU_PROPERTY(0x80000008, 0, EAX, 0, 7)
 #define X86_PROPERTY_MAX_VIRT_ADDR		KVM_X86_CPU_PROPERTY(0x80000008, 0, EAX, 8, 15)
+#define X86_PROPERTY_MAX_GUEST_PHY_ADDR		KVM_X86_CPU_PROPERTY(0x80000008, 0, EAX, 16, 23)
 #define X86_PROPERTY_SEV_C_BIT			KVM_X86_CPU_PROPERTY(0x8000001F, 0, EBX, 0, 5)
 #define X86_PROPERTY_PHYS_ADDR_REDUCTION	KVM_X86_CPU_PROPERTY(0x8000001F, 0, EBX, 6, 11)
 
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 74a4c736c9ae..aa9966ead543 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1293,10 +1293,16 @@ const struct kvm_cpuid2 *vcpu_get_supported_hv_cpuid(struct kvm_vcpu *vcpu)
 unsigned long vm_compute_max_gfn(struct kvm_vm *vm)
 {
 	const unsigned long num_ht_pages = 12 << (30 - vm->page_shift); /* 12 GiB */
-	unsigned long ht_gfn, max_gfn, max_pfn;
+	unsigned long ht_gfn, max_gfn, max_pfn, max_bits = 0;
 	uint8_t maxphyaddr;
 
-	max_gfn = (1ULL << (vm->pa_bits - vm->page_shift)) - 1;
+	if (kvm_cpu_has_p(X86_PROPERTY_MAX_GUEST_PHY_ADDR))
+		max_bits = kvm_cpu_property(X86_PROPERTY_MAX_GUEST_PHY_ADDR);
+
+	if (!max_bits)
+		max_bits = vm->pa_bits;
+
+	max_gfn = (1ULL << (max_bits - vm->page_shift)) - 1;
 
 	/* Avoid reserved HyperTransport region on AMD processors.  */
 	if (!host_cpu_is_amd)

base-commit: 448b3fe5a0eab5b625a7e15c67c7972169e47ff8
-- 
2.34.1