Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 16 Jun 2021 07:18:39 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Claire Chang <tientzu@chromium.org>
Cc:     Christoph Hellwig <hch@lst.de>, Rob Herring <robh+dt@kernel.org>,
        mpe@ellerman.id.au, Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        boris.ostrovsky@oracle.com, jgross@suse.com,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        benh@kernel.crashing.org, paulus@samba.org,
        "list@263.net:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
        sstabellini@kernel.org, Robin Murphy <robin.murphy@arm.com>,
        grant.likely@arm.com, xypron.glpk@gmx.de,
        Thierry Reding <treding@nvidia.com>, mingo@kernel.org,
        bauerman@linux.ibm.com, peterz@infradead.org,
        Greg KH <gregkh@linuxfoundation.org>,
        Saravana Kannan <saravanak@google.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        heikki.krogerus@linux.intel.com,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        linux-devicetree <devicetree@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        linuxppc-dev@lists.ozlabs.org, xen-devel@lists.xenproject.org,
        Nicolas Boichat <drinkcat@chromium.org>,
        Jim Quinlan <james.quinlan@broadcom.com>,
        Tomasz Figa <tfiga@chromium.org>, bskeggs@redhat.com,
        Bjorn Helgaas <bhelgaas@google.com>, chris@chris-wilson.co.uk,
        Daniel Vetter <daniel@ffwll.ch>, airlied@linux.ie,
        dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        jani.nikula@linux.intel.com, Jianxiong Gao <jxgao@google.com>,
        joonas.lahtinen@linux.intel.com, linux-pci@vger.kernel.org,
        maarten.lankhorst@linux.intel.com, matthew.auld@intel.com,
        rodrigo.vivi@intel.com, thomas.hellstrom@linux.intel.com
Subject: Re: [PATCH v11 09/12] swiotlb: Add restricted DMA alloc/free
 support
Message-ID: <20210616051839.GA27982@lst.de>
References: <20210616035240.840463-1-tientzu@chromium.org> <20210616035240.840463-10-tientzu@chromium.org> <CALiNf28=3vqAs+8HsjyBGOiPNR2F3yT6OGnLpZH_AkWqgTqgOA@mail.gmail.com> <20210616045918.GA27537@lst.de> <CALiNf2-+vL8rw5fi=DcR=V7d55Ls3-OXoxC87Pvrf1Kz14D_+A@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALiNf2-+vL8rw5fi=DcR=V7d55Ls3-OXoxC87Pvrf1Kz14D_+A@mail.gmail.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Precedence: bulk

On Wed, Jun 16, 2021 at 01:10:02PM +0800, Claire Chang wrote:
> On Wed, Jun 16, 2021 at 12:59 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > On Wed, Jun 16, 2021 at 12:04:16PM +0800, Claire Chang wrote:
> > > Just noticed that after propagating swiotlb_force setting into
> > > io_tlb_default_mem->force, the memory allocation behavior for
> > > swiotlb_force will change (i.e. always skipping arch_dma_alloc and
> > > dma_direct_alloc_from_pool).
> >
> > Yes, I think we need to split a "use_for_alloc" flag from the force flag.
> 
> How about splitting is_dev_swiotlb_force into is_swiotlb_force_bounce
> (io_tlb_mem->force_bounce) and is_swiotlb_force_alloc
> (io_tlb_mem->force_alloc)?

Yes, something like that.  I'd probably not use force for the alloc side
given that we otherwise never allocte from the swiotlb buffer.