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:   Wed, 23 Jan 2019 22:27:55 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Joerg Roedel <joro@8bytes.org>
Cc:     "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        virtualization@lists.linux-foundation.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        iommu@lists.linux-foundation.org, jfehlig@suse.com,
        jon.grimm@amd.com, brijesh.singh@amd.com, jroedel@suse.de
Subject: Re: [PATCH 2/5] swiotlb: Add is_swiotlb_active() function
Message-ID: <20190123212755.GA9032@lst.de>
References: <20190123163049.24863-1-joro@8bytes.org> <20190123163049.24863-3-joro@8bytes.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190123163049.24863-3-joro@8bytes.org>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jan 23, 2019 at 05:30:46PM +0100, Joerg Roedel wrote:
> +bool is_swiotlb_active(void)
> +{
> +	return !no_iotlb_memory;
> +}

As I've just introduced and fixed a bug in this area in the current
cycle - I don't think no_iotlb_memory is what your want (and maybe
not useful at all): if the arch valls swiotlb_exit after previously
initializing a buffer it won't be set.  You probably want to check
for non-zero io_tlb_start and/or io_tlb_end.