From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 108EE10F2; Thu, 12 Dec 2024 10:40:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734000060; cv=none; b=T0Fjqi5j1iDMyl0Qf4Y3PCyKVf9CafenszS66FaErqy9Di0HWwjtoTAjAMznLRUSmz0B4krUzGa3/m2yYQody1EE/CUA2o3JOt7mS0tD7vwANMmBwSYSlTI8jm/5yzeHvM4kPoEps+6vmNBWwjE4Wtz9+pELooB8h5bq7Vebs/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734000060; c=relaxed/simple; bh=vGlExwmxZcW3eZ2MdG0oaOnLiSi5C480ajsfsL6G6zg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hR/2nhsUxnwyS2TFAhmWNHG1JRqFtaqOYWfLm5oSVz0XgEJlj8MJU8N92cZnvXa3cVpkMbcqgHL9IC1e5vQpOIavTAiNRuu1bzc/NbHWpxlWq7+VFBOePc4NaOVBLJIAet7A8jhZST1pW6YsnfJNcCShLkf8uolVuWKgcWSIXHg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 79EF9169E; Thu, 12 Dec 2024 02:41:25 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 77F7F3F58B; Thu, 12 Dec 2024 02:40:54 -0800 (PST) Date: Thu, 12 Dec 2024 10:40:46 +0000 From: Mark Rutland To: Marc Zyngier Cc: Pavan Kondeti , Akhil P Oommen , Rob Clark , Sean Paul , Konrad Dybcio , Abhinav Kumar , Dmitry Baryshkov , Marijn Suijten , David Airlie , Simona Vetter , Elliot Berman , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] drm/msm/a6xx: Skip gpu secure fw load in EL2 mode Message-ID: References: <20241209-drm-msm-kvm-support-v1-1-1c983a8a8087@quicinc.com> <87ed2fs03w.wl-maz@kernel.org> <92cee905-a505-4ce9-9bbc-6fba4cea1d80@quicinc.com> <86sequsdtp.wl-maz@kernel.org> <87bjxhs2t7.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87bjxhs2t7.wl-maz@kernel.org> On Thu, Dec 12, 2024 at 08:50:12AM +0000, Marc Zyngier wrote: > On Thu, 12 Dec 2024 05:31:00 +0000, > Pavan Kondeti wrote: > > > > On Wed, Dec 11, 2024 at 10:40:02AM +0000, Marc Zyngier wrote: > > > On Wed, 11 Dec 2024 00:37:34 +0000, > > > Pavan Kondeti wrote: > > > > > > > > On Tue, Dec 10, 2024 at 09:24:03PM +0000, Marc Zyngier wrote: > > > > > > +static int a6xx_switch_secure_mode(struct msm_gpu *gpu) > > > > > > +{ > > > > > > + int ret; > > > > > > + > > > > > > +#ifdef CONFIG_ARM64 > > > > > > + /* > > > > > > + * We can access SECVID_TRUST_CNTL register when kernel is booted in EL2 mode. So, use it > > > > > > + * to switch the secure mode to avoid the dependency on zap shader. > > > > > > + */ > > > > > > + if (is_kernel_in_hyp_mode()) > > > > > > + goto direct_switch; > > > > > > > > > > No, please. To check whether you are *booted* at EL2, you need to > > > > > check for is_hyp_available(). Whether the kernel runs at EL1 or EL2 is > > > > > none of the driver's business, really. This is still absolutely > > > > > disgusting from an abstraction perspective, but I guess we don't have > > > > > much choice here. > > > > > > > > > > > > > Thanks Marc. Any suggestions on how we can make is_hyp_mode_available() > > > > available for modules? Do you prefer exporting > > > > kvm_protected_mode_initialized and __boot_cpu_mode symbols directly or > > > > try something like [1]? > > > > > > Ideally, neither. These were bad ideas nine years ago, and they still > > > are. The least ugly hack I can come up with is the patch below, and > > > you'd write something like: > > > > > > if (cpus_have_cap(ARM64_HAS_EL2_OWNERSHIP)) > > > blah(); > > > > > > This is obviously completely untested. > > > > > > > I have tested your patch. It works as intended. Thanks Marc. > > Note that you will probably get some push-back from the arm64 > maintainers on this front, because this is a fairly incomplete (and > fragile) solution. > > It would be much better if the discriminant came from the device tree. > After all, the hypervisor is fscking-up^W^Wchanging the programming > model of the GPU, and that should be reflected in the DT. Because for > all intent and purposes, this is not the same hardware anymore. FWIW I agree 100%, this should be described in DT. The cpucap doesn't describe the actual property we care about, and it cannot in general (e.g. for nested virt). I would strongly prefer to not have that as it's setting ourselves up for failure. > The GPU isn't the only device that needs fixing in that way: the > SMMUv3 needs to be exposed to the OS, and the PCIe ports need to be > linked to it and the ITS. So at the end of the day, detecting EL2 only > serves a limited purpose. You need to handle these cases, and might as > well put the GPU in the same bag. > > Which means that you'd either have a pair of static DTs (one that > exposes the brokenness of the firmware, and one that doesn't), or you > go the dtbhack route to compose the DT at boot time. Liekwise, agreed on all of this. Mark.