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Thu, 11 Sep 2025 06:40:11 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFy5YcFEvCgWHnvYA2CS0i/GVzCi6nkvSyRCO0Ot9zIMY1SZj9hEEJ47ZbDwq0R7VWjDIV9tg== X-Received: by 2002:a05:6000:430d:b0:3e7:4b1d:74e8 with SMTP id ffacd0b85a97d-3e74b1d750emr13662876f8f.26.1757598009386; Thu, 11 Sep 2025 06:40:09 -0700 (PDT) Received: from [192.168.10.48] ([151.95.56.250]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3e760778915sm2576343f8f.12.2025.09.11.06.40.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Sep 2025 06:40:08 -0700 (PDT) Message-ID: Date: Thu, 11 Sep 2025 15:40:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hpet: guard IRQ handling with BQL To: Igor Mammedov , qemu-devel@nongnu.org Cc: mst@redhat.com, =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= References: <20250910142506.86274-1-imammedo@redhat.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20250910142506.86274-1-imammedo@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/10/25 16:25, Igor Mammedov wrote: > Commit [1] made qemu fail with abort: > xen_evtchn_set_gsi: Assertion `bql_locked()' failed. > when running ./tests/functional/x86_64/test_kvm_xen.py tests. > > To fix it make sure that BQL is held when manipulating IRQs. Queued, but I think it's time to allow qemu_irq handlers to run outside the BQL. The idea would be to add qemu_allocate_irq_unlocked and qemu_allocate_irqs_unlocked, and add a boolean to IRQState. If the boolean is set (the default), qemu_set_irq would wrap the callback with bql_lock()/bql_unlock(). Together with the MMIO support that you introduced, this would allow making interrupt controllers BQL-free. Easier thread-safety would also, but I digress, provide a good reason to write even the simple devices in Rust---that's in my opinion an even better reason than memory safety, for which we already have developed lots of abstractions in QEMU. Paolo > Fixes: 7defb58baf (hpet: switch to fine-grained device locking) > Reported-by: Daniel P. Berrangé > Signed-off-by: Igor Mammedov > --- > hw/timer/hpet.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c > index 789a31d0a0..1acba4fa9d 100644 > --- a/hw/timer/hpet.c > +++ b/hw/timer/hpet.c > @@ -40,6 +40,7 @@ > #include "qom/object.h" > #include "qemu/lockable.h" > #include "qemu/seqlock.h" > +#include "qemu/main-loop.h" > #include "trace.h" > > struct hpet_fw_config hpet_fw_cfg = {.count = UINT8_MAX}; > @@ -222,12 +223,15 @@ static void update_irq(struct HPETTimer *timer, int set) > timer->fsb & 0xffffffff, MEMTXATTRS_UNSPECIFIED, > NULL); > } else if (timer->config & HPET_TN_TYPE_LEVEL) { > + BQL_LOCK_GUARD(); > qemu_irq_raise(s->irqs[route]); > } else { > + BQL_LOCK_GUARD(); > qemu_irq_pulse(s->irqs[route]); > } > } else { > if (!timer_fsb_route(timer)) { > + BQL_LOCK_GUARD(); > qemu_irq_lower(s->irqs[route]); > } > } > @@ -534,10 +538,12 @@ static void hpet_ram_write(void *opaque, hwaddr addr, > /* i8254 and RTC output pins are disabled > * when HPET is in legacy mode */ > if (activating_bit(old_val, new_val, HPET_CFG_LEGACY)) { > + BQL_LOCK_GUARD(); > qemu_set_irq(s->pit_enabled, 0); > qemu_irq_lower(s->irqs[0]); > qemu_irq_lower(s->irqs[RTC_ISA_IRQ]); > } else if (deactivating_bit(old_val, new_val, HPET_CFG_LEGACY)) { > + BQL_LOCK_GUARD(); > qemu_irq_lower(s->irqs[0]); > qemu_set_irq(s->pit_enabled, 1); > qemu_set_irq(s->irqs[RTC_ISA_IRQ], s->rtc_irq_level); > @@ -683,11 +689,13 @@ static void hpet_handle_legacy_irq(void *opaque, int n, int level) > > if (n == HPET_LEGACY_PIT_INT) { > if (!hpet_in_legacy_mode(s)) { > + BQL_LOCK_GUARD(); > qemu_set_irq(s->irqs[0], level); > } > } else { > s->rtc_irq_level = level; > if (!hpet_in_legacy_mode(s)) { > + BQL_LOCK_GUARD(); > qemu_set_irq(s->irqs[RTC_ISA_IRQ], level); > } > }