From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B73FB19DF5B for ; Fri, 7 Feb 2025 18:10:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738951852; cv=none; b=aG/ZWKAqXdrgSEPX28mh+QOPiYJiau/OcOFlr8h1R3nYNUSuzFkdvZnGTYS+W51aPBvxi5oAf2lMJ4UXZepgbcA5Gyg0kp9Al5ttExMXLUtNK9qKR9LkFOgsj+cFIYu7f665JPUBIVrpl3LmEdXs+G7v5yeWNNu00fWHsbdZZMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738951852; c=relaxed/simple; bh=MlvBE2BowHXDWbwjymFqCoSazPaseEcDREg8QI4ix3U=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=Fzx65Zen2aHDFHl2IIBI/1luDtWudG9OJWMgViAnydhtx4KTW9aFQ7ZnR63unFRUzGan1/AqIqgPsPKO10/0GXAggpy9RLlOPlanCpB4dic5ST3gjENEWr1LGWoOAdpUGFw+EDY9oR0CyFAb86BE6Ltk5ZB6yUg/yZN0jAPQyVQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qcg2Wqoo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qcg2Wqoo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 419ADC4CEDF; Fri, 7 Feb 2025 18:10:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738951852; bh=MlvBE2BowHXDWbwjymFqCoSazPaseEcDREg8QI4ix3U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qcg2Wqooswd9VWz+nlJX5lAmqZv/x7OO/B5x6jJRT9Jb+QygFwyFIPSd1XDOmRqQl ZRkrqW9KbTiZnh73FeDCDHPUyiXXZGm/wmpFlpvofRdY4+OitfDVkOdRnj0UOweZrw nNJMyKM0Gt1EDuUnRcFRutAfIwHdg9xQk7SAZZxUc6PjqKOVfbuB4M/QVcJic/y7VV wuKZcbLDWRIPQ8Gl+HeY473+fU52En0MYZ1JSK+7qUITgYHQpeySpRjBOQdm8+a4aW Xx9PsmPKWhwlYGAnuSRHIXH1ws9llqzC1k0WkbCC/z3fJPQdTze9YfZUkEh25MyGQF nf2uyxNP9rHpg== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1tgSoT-001jk8-S4; Fri, 07 Feb 2025 18:10:50 +0000 Date: Fri, 07 Feb 2025 18:10:49 +0000 Message-ID: <86ed09tyl2.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Alexander Potapenko , Joey Gouly , Suzuki K Poulose , Zenghui Yu Subject: Re: [PATCH 0/3] KVM: arm64: Assorted vgic fixes for 6.14 In-Reply-To: References: <20250206152100.1107909-1-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.4 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: oliver.upton@linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, glider@google.com, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Fri, 07 Feb 2025 18:03:55 +0000, Oliver Upton wrote: > > On Thu, Feb 06, 2025 at 03:20:57PM +0000, Marc Zyngier wrote: > > Alexander, while fuzzing KVM/arm64, found an annoying set of problems, > > all stemming from the fact that the vgic can be destroyed in parallel > > with the rest of the guest still being live. > > > > Yes, this is annoying. > > > > Fixing this is not going to happen overnight (though I have some > > ideas), but we can make what we have today a bit more robust. > > > > This is what patch #2 is doing. Patch #1 is just removing a loud > > WARN_ON() that serves little purpose, and patch #3 fixes the actual > > bug that Alex reported. > > > > Hopefully, none of that is controversial... > > I'm a bit grumbly about slapping bandaids on the problem, but given the > fact that glider reported all of this a while ago and we still haven't > fixed it is enough to justify these patches. So: Yeah, same here. I'm starting to think that we need to either prevent the vgic from being asynchronously destroyed, or start refcounting all IRQs just like LPIs. Which is very annoying since we don't have a global namespace for SGIs and PPIs. But maybe simply refcounting the vgic itself would be enough. Thoughts? > Reviewed-by: Oliver Upton Thanks, M. -- Without deviation from the norm, progress is not possible.