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:   Fri, 6 Nov 2020 19:24:24 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc:     Ashish Kalra <ashish.kalra@amd.com>, hch@lst.de,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        x86@kernel.org, luto@kernel.org, peterz@infradead.org,
        dave.hansen@linux-intel.com, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, brijesh.singh@amd.com,
        Thomas.Lendacky@amd.com, ssg.sos.patches@amd.com
Subject: Re: [PATCH v3] swiotlb: Adjust SWIOTBL bounce buffer size for SEV
 guests.
Message-ID: <20201106182424.GA9330@lst.de>
References: <20201104220804.21026-1-Ashish.Kalra@amd.com> <20201104221452.GA26079@char.us.oracle.com> <20201104223913.GA25311@ashkalra_ubuntu_server> <20201105174317.GA4294@char.us.oracle.com> <20201105184115.GA25261@ashkalra_ubuntu_server> <20201105190649.GB5366@char.us.oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20201105190649.GB5366@char.us.oracle.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Precedence: bulk

On Thu, Nov 05, 2020 at 02:06:49PM -0500, Konrad Rzeszutek Wilk wrote:
> .
> > > Right, so I am wondering if we can do this better.
> > > 
> > > That is you are never going to get any 32-bit devices with SEV right? That
> > > is there is nothing that bounds you to always use the memory below 4GB?
> > > 
> > 
> > We do support 32-bit PCIe passthrough devices with SEV.
> 
> Ewww..  Which devices would this be?

There is still some new broken shit like that that keeps appearing.
GPU is pretty famouts for supporting less than 64-bit addressing,
even if it isn't all the way down to 32-bit.