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Fri, 31 Jul 2020 09:08:41 +0100 MIME-Version: 1.0 Date: Fri, 31 Jul 2020 09:08:41 +0100 From: Marc Zyngier To: Valentin Schneider Subject: Re: [PATCH v2 2/2] irqchip/gic-v2, v3: Prevent SW resends entirely In-Reply-To: References: <20200730170321.31228-1-valentin.schneider@arm.com> <20200730170321.31228-3-valentin.schneider@arm.com> User-Agent: Roundcube Webmail/1.4.5 Message-ID: <10da73b8a8937b08b0993513d6c20e98@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: valentin.schneider@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, jason@lakedaemon.net, Lorenzo.Pieralisi@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200731_040844_385289_18AD5976 X-CRM114-Status: GOOD ( 26.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Gleixner , Lorenzo Pieralisi , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jason Cooper Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Valentin, On 2020-07-31 01:08, Valentin Schneider wrote: > Hi Marc, > > On 30/07/20 19:10, Marc Zyngier wrote: > [...] >>> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c >>> index e2b4cae88bce..a91ce1e73bd2 100644 >>> --- a/drivers/irqchip/irq-gic.c >>> +++ b/drivers/irqchip/irq-gic.c >>> @@ -983,6 +983,7 @@ static int gic_irq_domain_map(struct irq_domain >>> *d, unsigned int irq, >>> irq_hw_number_t hw) >>> { >>> struct gic_chip_data *gic = d->host_data; >>> + struct irq_data *irqd = irq_desc_get_irq_data(irq_to_desc(irq)); >>> >>> if (hw < 32) { >>> irq_set_percpu_devid(irq); >>> @@ -992,8 +993,11 @@ static int gic_irq_domain_map(struct irq_domain >>> *d, unsigned int irq, >>> irq_domain_set_info(d, irq, hw, &gic->chip, >>> d->host_data, >>> handle_fasteoi_irq, NULL, NULL); >>> irq_set_probe(irq); >>> - irqd_set_single_target(irq_desc_get_irq_data(irq_to_desc(irq))); >>> + irqd_set_single_target(irqd); >>> } >>> + >>> + /* Prevents SW retriggers which mess up the ACK/EOI ordering */ >>> + irqd_set_handle_enforce_irqctx(irqd); >>> return 0; >>> } >> >> I'm OK with this in principle, but this requires additional changes >> in the rest of the GIC universe. The ITS driver needs to provide its >> own >> retrigger function for LPIs (queuing an INT command), and any of the >> SPI generating widgets that can be stacked on top of a GIC (GICv3-MBI, >> GICv2m, and all the other Annapurna/Marvell/NVDIA wonders need to gain >> directly or indirectly a call to irq_chip_retrigger_hierarchy(). >> > > Eep, yes indeed... I didn't see that can was full of worms, though even > if > it only really matters for eoimode=0 I think it might still be worth it > (if only to respect the spec). Well, given that we are using EOImode=0 for all guests at the moment, there is some value it getting it right! ;-) > >> We can probably avoid changing the MSI widgets by teaching the MSI >> code about the HW retrigger, but a number of other non-MSI drivers >> will need some help... >> >> I'll have a look tomorrow. >> > > For LPIs AFAICT we could directly reuse its_irq_set_irqchip_state() - I > see > the VPE side of things already has a HW retrigger callback. Yes, that's the idea (in general, if you implement the PENDING side of irq_set_irqchip_state(), retrigger comes for free). > For gicv2m, I *think* we'd want irq_chip_retrigger_hierarchy() on both > MSI > domains (which IIUC you suggest might be doable by adding the retrigger > as > a default MSI chip op). Yes, that was my idea. > I'm not very familiar with the rest of the fauna, so I'll have to do > some > reading tomorrow as well; it's probably high time for me to actually > read > up on LPIs & ITS while I'm at it... Look for anything that performs an interrupt allocation by calling into the parent with a 3 cell (DT case) fwspec. There is a bunch of them. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel