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Fri, 20 Jun 2025 12:04:20 -0700 (PDT) Date: Fri, 20 Jun 2025 12:04:19 -0700 In-Reply-To: Mime-Version: 1.0 References: <20250611224604.313496-2-seanjc@google.com> <20250611224604.313496-4-seanjc@google.com> <86tt4lcgs3.wl-maz@kernel.org> Message-ID: Subject: Re: [PATCH v3 02/62] KVM: arm64: WARN if unmapping vLPI fails From: Sean Christopherson To: Oliver Upton Cc: Marc Zyngier , Paolo Bonzini , Joerg Roedel , David Woodhouse , Lu Baolu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Sairaj Kodilkar , Vasant Hegde , Maxim Levitsky , Joao Martins , Francesco Lavra , David Matlack Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250620_120422_209530_8A60A72E X-CRM114-Status: GOOD ( 29.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jun 20, 2025, Oliver Upton wrote: > On Fri, Jun 20, 2025 at 10:22:32AM -0700, Sean Christopherson wrote: > > On Fri, Jun 13, 2025, Oliver Upton wrote: > > > On Thu, Jun 12, 2025 at 07:34:35AM -0700, Sean Christopherson wrote: > > > > On Thu, Jun 12, 2025, Marc Zyngier wrote: > > > > > But not having an VLPI mapping for an interrupt at the point where we're > > > > > tearing down the forwarding is pretty benign. IRQs *still* go where they > > > > > should, and we don't lose anything. > > > > > > The VM may not actually be getting torn down, though. The series of > > > fixes [*] we took for 6.16 addressed games that VMMs might be playing on > > > irqbypass for a live VM. > > > > > > [*] https://lore.kernel.org/kvmarm/20250523194722.4066715-1-oliver.upton@linux.dev/ > > > > > > > All of those failure scenario seem like warnable offences when KVM thinks it has > > > > configured the IRQ to be forwarded to a vCPU. > > > > > > I tend to agree here, especially considering how horribly fragile GICv4 > > > has been in some systems. I know of a couple implementations where ITS > > > command failures and/or unmapped MSIs are fatal for the entire machine. > > > Debugging them has been a genuine pain in the ass. > > > > > > WARN'ing when state tracking for vLPIs is out of whack would've made it > > > a little easier. > > > > Marc, does this look and read better? > > > > I'd really, really like to get this sorted out asap, as it's the only thing > > blocking the series, and I want to get the series into linux-next early next > > week, before I go OOO for ~10 days. > > Can you just send it out as a standalone patch? It's only tangientally > related to the truckload of x86 stuff The issue is that "KVM: Don't WARN if updating IRQ bypass route fails" directly depends on both this patch and decent chunk of the x86 crud. I could probably trim some of the x86 crud by reshuffling patches around, but I can't get rid of it entirely. > that I'd rather not pull in the event of conflict resolution. LOL, why not? :-) If I post it as a standalone patch, could you/Marc put it into a stable topic branch based on kvm/master? (kvm/master now has patch 1, yay!) Then I can create a topic branch for this mountain of stuff based on the arm64 topic branch.