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Wed, 09 Sep 2026 01:17:10 -0700 (PDT) X-Received: by 2002:a5d:6f03:0:b0:485:ad55:208d with SMTP id ffacd0b85a97d-485ad552246mr6292364f8f.18.1788941830229; Wed, 09 Sep 2026 01:17:10 -0700 (PDT) Received: from imammedo ([213.175.46.86]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4859162f354sm34825586f8f.20.2026.09.09.01.17.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 01:17:09 -0700 (PDT) Date: Wed, 9 Sep 2026 10:17:08 +0200 From: Igor Mammedov To: Peter Maydell Cc: qemu-devel@nongnu.org, leif.lindholm@oss.qualcomm.com, eauger@redhat.com Subject: Re: [PATCH 0/6] sbsa-gwdt cleanup and fixes Message-ID: <20260909101708.23c6e37f@imammedo> In-Reply-To: References: <20260902122646.2848464-1-imammedo@redhat.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=imammedo@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_H2=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: qemu development 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 Tue, 8 Sep 2026 16:08:35 +0100 Peter Maydell wrote: > On Wed, 2 Sept 2026 at 13:26, Igor Mammedov wrote: > > > > > > Series picks up dropped gwdt fixes from > > > > [PATCH v3 00/17] Add watchdog support to arm/virt board > > https://patchew.org/QEMU/20260624102830.1355552-1-imammedo@redhat.com/ > > > > patches were basically rewritten to make changes simpler/easier to reson about. > > > > patch 6/6 is partial fix with open question: > > > > sbsa-gwdt currently mantains WVC in since VM start ticks, which works fine under > > TCG. However under KVM those system counter domains diverge and CNTPCT in guest > > starts to return host's value. As result WCV reads/writes got mixed up with > > QEMU still assuming VM timeframe while guest using host's one. > > Question is how should we fix it? > > Presumably we should be dealing in deltas from the > QEMU_CLOCK_VIRTUAL value? deltas could works as workaround at cost of polluting sbsa-gwdt device model with KVM quirk. but then real fun begins when we bring in picture migration (even not counting CNTPCT jump), WCV would either diverge or jump as well => more KVM quirks in whatchdog code to deal with. I'd think that we would want to track QEMU_CLOCK_VIRTUAL in WCV, basically make CNTPCT = CNTVCT and treat as such everywhere. What is lost on me is history/reasoning why CNTPCT tracks host value? Why can't we make it track virtual clock instead (there is KVM_ARM_SET_COUNTER_OFFSET that supposedly should do the job)? > Anyway, for this series, since the only thing I wanted to change > was expanding a comment, I'll apply this to target-arm.next and > make that tweak there. Thanks! > > -- PMM >