On 12/12/2023 12:47 PM, Shashar, Sagi wrote:

-----Original Message----- From: Sagi Shahar sagis@google.com Sent: Tuesday, December 12, 2023 12:47 PM To: linux-kselftest@vger.kernel.org; Ackerley Tng ackerleytng@google.com; Afranji, Ryan afranji@google.com; Aktas, Erdem erdemaktas@google.com; Sagi Shahar sagis@google.com; Yamahata, Isaku isaku.yamahata@intel.com Cc: Sean Christopherson seanjc@google.com; Paolo Bonzini pbonzini@redhat.com; Shuah Khan shuah@kernel.org; Peter Gonda pgonda@google.com; Xu, Haibo1 haibo1.xu@intel.com; Chao Peng chao.p.peng@linux.intel.com; Annapurve, Vishal vannapurve@google.com; Roger Wang runanwang@google.com; Vipin Sharma vipinsh@google.com; jmattson@google.com; dmatlack@google.com; linux-kernel@vger.kernel.org; kvm@vger.kernel.org; linux-mm@kvack.org Subject: [RFC PATCH v5 27/29] KVM: selftests: Propagate KVM_EXIT_MEMORY_FAULT to userspace

Allow userspace to handle KVM_EXIT_MEMORY_FAULT instead of triggering TEST_ASSERT.

From the KVM_EXIT_MEMORY_FAULT documentation: Note! KVM_EXIT_MEMORY_FAULT is unique among all KVM exit reasons in that it accompanies a return code of '-1', not '0'! errno will always be set to EFAULT or EHWPOISON when KVM exits with KVM_EXIT_MEMORY_FAULT, userspace should assume kvm_run.exit_reason is stale/undefined for all other error numbers.

If KVM exits to userspace with KVM_EXIT_MEMORY_FAULT, most likely it's because the guest attempts to access the gfn in a way that is different from what the KVM is configured, in terms of private/shared property. I'd suggest to drop this patch and work on the selftests code to eliminate this exit.

If we need a testcase to catch this exit intentionally, we may call _vcpu_run() directly from the testcase and keep the common API vcpu_run() intact.

Signed-off-by: Sagi Shahar sagis@google.com

tools/testing/selftests/kvm/lib/kvm_util.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index d024abc5379c..8fb041e51484 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -1742,6 +1742,10 @@ void vcpu_run(struct kvm_vcpu *vcpu) { int ret = _vcpu_run(vcpu);

• // Allow this scenario to be handled by the caller.
• if (ret == -1 && errno == EFAULT)

• return;
  

• TEST_ASSERT(!ret, KVM_IOCTL_ERROR(KVM_RUN, ret)); }

2.43.0.472.g3155946c3a-goog