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Kernel. Org" Subject: Re: [PATCH v2 8/8] habanalabs: enable 64-bit DMA mask in POWER9 Message-ID: <20190612065314.GA28838@infradead.org> References: <20190611092144.11194-1-oded.gabbay@gmail.com> <20190611095857.GB24058@kroah.com> <20190611151753.GA11404@infradead.org> <20190611152655.GA3972@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 12, 2019 at 04:35:22PM +1000, Oliver O'Halloran wrote: > Setting a 48 bit DMA mask doesn't work today because we only allocate > IOMMU tables to cover the 0..2GB range of PCI bus addresses. I don't think that is true upstream, and if it is we need to fix bug in the powerpc code. powerpc should be falling back treating a 48-bit dma mask like a 32-bit one at least, that is use dynamic iommu mappings instead of using the direct mapping. And from my reding of arch/powerpc/kernel/dma-iommu.c that is exactly what it does.