Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 20 Sep 2019 18:38:43 +0200
From:   Jean-Philippe Brucker <jean-philippe@linaro.org>
To:     Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc:     iommu@lists.linux-foundation.org,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH 4/4] iommu: Introduce guest PASID bind function
Message-ID: <20190920163843.GD1533866@lophozonia>
References: <1568849194-47874-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1568849194-47874-5-git-send-email-jacob.jun.pan@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1568849194-47874-5-git-send-email-jacob.jun.pan@linux.intel.com>
User-Agent: Mutt/1.12.1 (2019-06-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Sep 18, 2019 at 04:26:34PM -0700, Jacob Pan wrote:
> Guest shared virtual address (SVA) may require host to shadow guest
> PASID tables. Guest PASID can also be allocated from the host via
> enlightened interfaces. In this case, guest needs to bind the guest
> mm, i.e. cr3 in guest physical address to the actual PASID table in
> the host IOMMU. Nesting will be turned on such that guest virtual
> address can go through a two level translation:
> - 1st level translates GVA to GPA
> - 2nd level translates GPA to HPA
> This patch introduces APIs to bind guest PASID data to the assigned
> device entry in the physical IOMMU. See the diagram below for usage
> explaination.

explanation

Otherwise Looks fine to me. I was wondering if we would be able to reuse
the API for Arm SMMUv2, which allows nesting translation, but without
PASID - there is a single address space per device, with two stages of
translation. I think it would work, although it would look better with
something like "PGD" instead of "PASID" in the API names (e.g.
iommu_sva_bind_gpgd) since that case wouldn't use PASID at all. But I
don't want to quibble over names, so

Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>