[PATCH] selftests: KVM: avoid failures due to reserved HyperTransport region

[Paolo Bonzini <pbonzini@redhat.com>]

Accessing guest physical addresses at 0xFFFD_0000_0000 and above causes
a failure on AMD processors because those addresses are reserved by
HyperTransport (this is not documented).  Avoid selftests failures
by reserving those guest physical addresses.

Fixes: ef4c9f4f6546 ("KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()")
Cc: stable@vger.kernel.org
Cc: David Matlack <dmatlack@google.com>
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 10a8ed691c66..d995cc9836ee 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -309,6 +309,12 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
 	/* Limit physical addresses to PA-bits. */
 	vm->max_gfn = ((1ULL << vm->pa_bits) >> vm->page_shift) - 1;
 
+#ifdef __x86_64__
+	/* Avoid reserved HyperTransport region on AMD processors.  */
+	if (vm->pa_bits == 48)
+		vm->max_gfn = 0xfffcfffff;
+#endif
+
 	/* Allocate and setup memory for guest. */
 	vm->vpages_mapped = sparsebit_alloc();
 	if (phy_pages != 0)
-- 
2.27.0