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[174.93.89.196]) by smtp.gmail.com with ESMTPSA id g11sm1011865qkl.30.2020.11.06.10.06.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2020 10:06:12 -0800 (PST) Date: Fri, 6 Nov 2020 13:06:10 -0500 From: Peter Xu To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , "Dr . David Alan Gilbert" , Andrew Jones Subject: Re: [PATCH v13 13/14] KVM: selftests: Let dirty_log_test async for dirty ring test Message-ID: <20201106180610.GC138364@xz-x1> References: <20201001012044.5151-1-peterx@redhat.com> <20201001012239.6159-1-peterx@redhat.com> <6d5eb99e-e068-e5a6-522f-07ef9c33127f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <6d5eb99e-e068-e5a6-522f-07ef9c33127f@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Nov 06, 2020 at 12:27:54PM +0100, Paolo Bonzini wrote: > On 01/10/20 03:22, Peter Xu wrote: > > + > > +static void vcpu_sig_handler(int sig) > > +{ > > + TEST_ASSERT(sig == SIG_IPI, "unknown signal: %d", sig); > > +} > > + > > Unless you also use run->immediate_exit in vcpu_kick, this is racy. The > alternative is to _not_ set up a signal handler and instead block the > signal. KVM_SET_SIGNAL_MASK unblocks the signal inside the VM and on -EINTR > sigwait accepts the signal (removes it from the set of pending signal). Thanks for picking up the series! I think you're right. One trivial comment below: > > This is a bit more complicated, but I think it's a good idea to do it this > way for documentation purposes. Here is the patch: > > diff --git a/tools/testing/selftests/kvm/dirty_log_test.c > b/tools/testing/selftests/kvm/dirty_log_test.c > index 4b404dfdc2f9..9a5b876b74af 100644 > --- a/tools/testing/selftests/kvm/dirty_log_test.c > +++ b/tools/testing/selftests/kvm/dirty_log_test.c > @@ -172,11 +172,6 @@ static pthread_t vcpu_thread; > /* Only way to pass this to the signal handler */ > static struct kvm_vm *current_vm; > > -static void vcpu_sig_handler(int sig) > -{ > - TEST_ASSERT(sig == SIG_IPI, "unknown signal: %d", sig); > -} > - > static void vcpu_kick(void) > { > pthread_kill(vcpu_thread, SIG_IPI); > @@ -484,13 +479,26 @@ static void *vcpu_worker(void *data) > struct kvm_vm *vm = data; > uint64_t *guest_array; > uint64_t pages_count = 0; > - struct sigaction sigact; > + struct kvm_signal_mask *sigmask = alloca(offsetof(struct kvm_signal_mask, > sigset) > + + sizeof(sigset_t)); > + sigset_t *sigset = (sigset_t *) &sigmask->sigset; > > current_vm = vm; > vcpu_fd = vcpu_get_fd(vm, VCPU_ID); > - memset(&sigact, 0, sizeof(sigact)); > - sigact.sa_handler = vcpu_sig_handler; > - sigaction(SIG_IPI, &sigact, NULL); > + > + /* > + * SIG_IPI is unblocked atomically while in KVM_RUN. It causes the > + * ioctl to return with -EINTR, but it is still pending and we need > + * to accept it with the sigwait. > + */ > + sigmask->len = 8; > + pthread_sigmask(0, NULL, sigset); Not extremely important, but still better with SIG_BLOCK imho, since it seems not all archs defined SIG_BLOCK as zero. > + vcpu_ioctl(vm, VCPU_ID, KVM_SET_SIGNAL_MASK, sigmask); > + sigaddset(sigset, SIG_IPI); > + pthread_sigmask(SIG_BLOCK, sigset, NULL); > + > + sigemptyset(sigset); > + sigaddset(sigset, SIG_IPI); > > guest_array = addr_gva2hva(vm, (vm_vaddr_t)random_array); > > @@ -500,6 +508,11 @@ static void *vcpu_worker(void *data) > pages_count += TEST_PAGES_PER_LOOP; > /* Let the guest dirty the random pages */ > ret = ioctl(vcpu_fd, KVM_RUN, NULL); > + if (ret == -EINTR) { > + int sig = -1; > + sigwait(sigset, &sig); > + assert(sig == SIG_IPI); > + } > log_mode_after_vcpu_run(vm, ret, errno); > } > -- Peter Xu