From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0D18247798B; Tue, 1 Sep 2026 09:17:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788254234; cv=none; b=R6cAk+8zVEEiWAsP5CGYs+kjKRtX2ikhG2utAVONJyxogtpcefZ9QRM5xgLnZ/rc0N3tAMacE5SZa4AuwBq8UksLKS+4d34yerqPvC0ksqQwmxCdHR0Wp+UPBFZ0JoSKclqZcb2Awr9m/iPAwc5TJkhJQtCV4H9On0Cy6HX+bPc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788254234; c=relaxed/simple; bh=SEvxqsLXA5gPmTU0Dj4YKtTfRCn4/vTp5S4oMrM7tGk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=BJKM/XJRTx1Bm2jdEKprB4xv+tnajlO+MDPkfDN4+czk8XIz8NHFsCnPCmyDKbldp+hyE6iba0YDwckprMli1Cz28IJ4LJwoN/9Qrrhk9EtWr6qRoJhbybMd37PRLeLMIMh1czos4LK3leGktlelWxDEZ38xWc3rIsTLntLwEW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XROMNIUm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XROMNIUm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A4EB61F000E9; Tue, 1 Sep 2026 09:17:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788254232; bh=mITZlxCGGk5dvksU48UBQe0WaGaTY/+s4dpeJMto630=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=XROMNIUmyhA7M/dbxKK8Imo86dz2L5j/zRFqHXNrxib/St5Bz1Wb45NtmhWOw5fJy 1u3rgOng700Q/MQ7vgjnccFx73xrQm/I7XQ3n67GRnFhDKxJ/VFmyX48m+SserSxs+ Tj82D7pJJMB26AvoXAgxRVqAW3LgHXg+Khq3BxBKr9/K3b1pItu8VaSk4UULn1gG// 8C8f2gKAHAI74TDde4b39ZA0HPi0d9Z3mFhPd6KgiQH0aY3Zq0mWuwzTsGSVTSS7ZE jUydPyVjl+1VTyXdmpr4NjgMXIHt/C0EyY7NN9kjEfZOHNqNA5Ed9dbgxa4YiD6AJE VftVrjb3WsNrg== X-Mailer: emacs 31.1 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Nicolin Chen Cc: linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Alexey Kardashevskiy , Catalin Marinas , Dan Williams , Jason Gunthorpe , Joerg Roedel , Jonathan Cameron , Marc Zyngier , Pranjal Shrivastava , Robin Murphy , Samuel Ortiz , Steven Price , Suzuki K Poulose , Will Deacon , Xu Yilun Subject: Re: [RFC PATCH v4 03/16] iommu/arm-smmu-v3: Add initial pSMMU realm viommu plumbing In-Reply-To: References: <20260427085344.941627-1-aneesh.kumar@kernel.org> <20260427085344.941627-4-aneesh.kumar@kernel.org> Date: Tue, 01 Sep 2026 14:47:04 +0530 Message-ID: Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Nicolin Chen writes: > On Mon, Apr 27, 2026 at 02:23:31PM +0530, Aneesh Kumar K.V (Arm) wrote: >> +static const struct iommufd_viommu_ops arm_realm_smmu_v3_ops = { >> + .destroy = arm_realm_smmu_v3_destroy, >> + .alloc_domain_nested = arm_vsmmu_alloc_domain_nested, >> + .cache_invalidate = arm_vsmmu_cache_invalidate, > > I don't think realm vsmmu should include NS nested domain ops. I > wonder if adding here is for some covert reason that prevents us > from registering viommu/vdevice objects? > >> +static int arm_realm_smmu_v3_vdevice_init(struct iommufd_vdevice *vdev) >> +{ >> + struct device *dev = iommufd_vdevice_to_device(vdev); >> + struct arm_smmu_master *master = dev_iommu_priv_get(dev); >> + // fixme which stream to pick >> + /* At this moment, iommufd only supports PCI device that has one SID */ >> + struct arm_smmu_stream *stream = &master->streams[0]; >> + struct arm_smmu_device *smmu = master->smmu; >> + unsigned long rmi_ret = 0; >> + int ret; >> + >> + if (!smmu->realm_initialized) >> + return -EINVAL; >> + >> + ret = rmi_psmmu_st_l2_create(smmu->base_phys, >> + ALIGN_DOWN(stream->id, STRTAB_NUM_L2_STES), >> + &rmi_ret); > > The "vdevice" is for a PSMMU stream table allocation.. > >> +int arm_realm_smmu_v3_init(struct iommufd_viommu *viommu, >> + const struct iommu_user_data *user_data) >> +{ > [...] >> +psmmu_activate: >> + ret = rmi_psmmu_activate(smmu->base_phys, virt_to_phys(params), >> + &rmi_ret); > > .. and the "viommu" is also for PSMMU activation... > >> +++ b/include/uapi/linux/iommufd.h >> @@ -1055,6 +1055,7 @@ enum iommu_viommu_type { >> IOMMU_VIOMMU_TYPE_DEFAULT = 0, >> IOMMU_VIOMMU_TYPE_ARM_SMMUV3 = 1, >> IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV = 2, >> + IOMMU_VIOMMU_TYPE_ARM_REALM_SMMUV3 = 3, > > .. and we demand userspace (VMM) to use IOMMU_VIOMMU_ALLOC ioctl, > even if VMM does not actually expose a guest-level SMMU instance. > Thus, no user_data. > > I can get the reasoning behind the flow using this viommu/vdevice. > > But, on the other hand, I can imagine that a Realm VSMMU would add > a new flag with a user_data to this VIOMMU. Then, this flow would > give some troubles to VMM (QEMU for example): > > - For VM with a guest-level SMMU, QEMU creates a realm instance > where IOMMU_VIOMMU_TYPE_ARM_REALM_SMMUV3 (with vsmmu) can be > allocated. > - For VM w/o a guest-level SMMU, QEMU won't create such a realm > instance, while still required to invoke the ioctl (w/o vsmmu). > > Taking a step back, I wonder if we really need to use iommufd for > PSMMU activation and its stream table allocations? > > Here are some facts: > - An iommufd has a ctx, that's one per VM. Similarly, a Realm > has an RD. > - For an RMI command that needs an RD, it makes sense to be per > iommufd ctx, e.g. RMI_VSMMU_* or RMI_VDEV_* commands. > - PSMMU commands are global; they don't need RD. So they don't > seem necessary to tie to an iommufd ctx. > > Instead, could the PSMMU activation be done after RMI_PSMMU_INFO > check? Is there any reason not to do that? A safer timing might > be at the device assignment stage? > One of the reasons I added IOMMU_VIOMMU_TYPE_ARM_REALM_SMMUV3 was to avoid creating a psmmu object when we are not using a PCI passthrough VM. That is also the reason for all the refcounting around the psmmu objects. If we are okay with creating psmmu objects early, then I guess we can go with the above approach. > > Speaking of which, RMI_PSMMU_ST_L2_CREATE doesn't seem necessary > to be invoked in a vdevice context either. Maybe it should align > with iommufd idev's lifecycle? > -aneesh