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:   Mon, 2 Dec 2019 20:07:31 -0800
From:   Ram Pai <linuxram@us.ibm.com>
To:     Alexey Kardashevskiy <aik@ozlabs.ru>
Cc:     linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au,
        benh@kernel.crashing.org, david@gibson.dropbear.id.au,
        paulus@ozlabs.org, mdroth@linux.vnet.ibm.com, hch@lst.de,
        andmike@us.ibm.com, sukadev@linux.vnet.ibm.com, mst@redhat.com,
        ram.n.pai@gmail.com, cai@lca.pw, tglx@linutronix.de,
        bauerman@linux.ibm.com, linux-kernel@vger.kernel.org
Reply-To: Ram Pai <linuxram@us.ibm.com>
References: <1575269124-17885-1-git-send-email-linuxram@us.ibm.com>
 <1575269124-17885-2-git-send-email-linuxram@us.ibm.com>
 <1575269124-17885-3-git-send-email-linuxram@us.ibm.com>
 <58b08d09-aaf8-5659-c4e8-c502c508f35c@ozlabs.ru>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <58b08d09-aaf8-5659-c4e8-c502c508f35c@ozlabs.ru>
User-Agent: Mutt/1.5.21 (2010-09-15)
Message-Id: <20191203040731.GC12354@oc0525413822.ibm.com>
Subject: RE: [PATCH v4 2/2] powerpc/pseries/iommu: Use dma_iommu_ops for Secure VMs
 aswell.
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Dec 03, 2019 at 11:58:18AM +1100, Alexey Kardashevskiy wrote:
> 
> 
> On 02/12/2019 17:45, Ram Pai wrote:
> > Commit edea902c1c1e ("powerpc/pseries/iommu: Don't use dma_iommu_ops on
> > 	       secure guests")
> > disabled dma_iommu_ops path, for secure VMs. The rationale for disabling
> > the dma_iommu_ops path, was to use the dma_direct path, since it had
> > inbuilt support for bounce-buffering through SWIOTLB.
> > 
> > However dma_iommu_ops is functionally much richer. Depending on the
> > capabilities of the platform, it can handle direct DMA; with or without
> > bounce buffering, and it can handle indirect DMA. Hence its better to
> > leverage the richer functionality supported by dma_iommu_ops.
> 
> What exactly do we leverage after applying this patch? afaict things are
> going to work in exact same old way with this applied, no? Thanks,

Yes. You got it right. Another way of saying this is, it reverts the changes.

RP