[PATCH] KVM: selftests: Create memslot 0 at GPA 0x100000000 on x86_64

From: David Matlack <dmatlack@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>
Cc: Fuad Tabba <tabba@google.com>, Peter Gonda <pgonda@google.com>,
	 Ackerley Tng <ackerleytng@google.com>,
	Chao Peng <chao.p.peng@linux.intel.com>,
	 Vishal Annapurve <vannapurve@google.com>,
	Michael Roth <michael.roth@amd.com>,
	 Andrew Jones <ajones@ventanamicro.com>,
	kvm@vger.kernel.org,  David Matlack <dmatlack@google.com>
Subject: [PATCH] KVM: selftests: Create memslot 0 at GPA 0x100000000 on x86_64
Date: Thu,  7 Mar 2024 11:42:55 -0800	[thread overview]
Message-ID: <20240307194255.1367442-1-dmatlack@google.com> (raw)

Create memslot 0 at 0x100000000 (4GiB) to avoid it overlapping with
KVM's private memslot for the APIC-access page.

Without this change running large-enough selftests (high number of vCPUs
and/or guest memory) can result in KVM_CREATE_VCPU failing because the
APIC-access page memslot overlaps memslot 0 created by the selftest:

  $ ./dirty_log_perf_test -v 256 -s anonymous_hugetlb_1gb -b 4G
  Test iterations: 2
  Testing guest mode: PA-bits:ANY, VA-bits:48,  4K pages
  ==== Test Assertion Failure ====
    lib/kvm_util.c:1341: vcpu->fd >= 0
    pid=53654 tid=53654 errno=17 - File exists
    (stack trace empty)
    KVM_CREATE_VCPU failed, rc: -1 errno: 17 (File exists)

Signed-off-by: David Matlack <dmatlack@google.com>
---
 tools/testing/selftests/kvm/include/x86_64/processor.h | 6 ++++++
 tools/testing/selftests/kvm/lib/kvm_util.c             | 7 ++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 3bd03b088dda..ee33528007ee 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -20,6 +20,12 @@
 
 #include "../kvm_util.h"
 
+/*
+ * Create memslot 0 at 4GiB to avoid overlapping with KVM's private memslot for
+ * the APIC-access page at 0xfee00000.
+ */
+#define KVM_UTIL_MEMSLOT0_GPA 0x100000000ULL
+
 extern bool host_cpu_is_intel;
 extern bool host_cpu_is_amd;
 
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index b2262b5fad9e..c8d7e66d308d 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -20,6 +20,10 @@
 
 #define KVM_UTIL_MIN_PFN	2
 
+#ifndef KVM_UTIL_MEMSLOT0_GPA
+#define KVM_UTIL_MEMSLOT0_GPA 0ULL
+#endif
+
 static int vcpu_mmap_sz(void);
 
 int open_path_or_exit(const char *path, int flags)
@@ -418,7 +422,8 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus,
 
 	vm = ____vm_create(shape);
 
-	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, nr_pages, 0);
+	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+				    KVM_UTIL_MEMSLOT0_GPA, 0, nr_pages, 0);
 	for (i = 0; i < NR_MEM_REGIONS; i++)
 		vm->memslots[i] = 0;
 

base-commit: 0c64952fec3ea01cb5b09f00134200f3e7ab40d5
-- 
2.44.0.278.ge034bb2e1d-goog

