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[2003:cb:c740:6200:84e1:eabc:8e2:7429]) by smtp.gmail.com with ESMTPSA id y25-20020a7bcd99000000b003fc04eb92cbsm2741669wmj.44.2023.07.18.11.05.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Jul 2023 11:05:03 -0700 (PDT) Message-ID: <2556f0dd-d951-c21f-0e2e-7f2bb8d9fab3@redhat.com> Date: Tue, 18 Jul 2023 20:05:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2 2/2] udmabuf: Add back support for mapping hugetlb pages (v2) To: Vivek Kasireddy , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, Mike Kravetz Cc: Hugh Dickins , Peter Xu , Jason Gunthorpe , Gerd Hoffmann , Dongwon Kim , Junxiao Chang References: <20230718082605.1570740-1-vivek.kasireddy@intel.com> <20230718082605.1570740-3-vivek.kasireddy@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230718082605.1570740-3-vivek.kasireddy@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: BF6DF40018 X-Stat-Signature: pue5dxk98s6x9fn1imuwfypuj1tzpzmr X-HE-Tag: 1689703507-970039 X-HE-Meta: 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 ytQjylRO Pt7pRrHC4eI1+h4yyjgaNglFsa3NfqxgnT39owd5hicv+YeDr4FNCSr2h/CH6L1iX9GAuOoQo2783qzumYMK6gJhrGVHBW4gIrs5KlwPbBR5U2tX+eQBtBM4jCNxIp3YoO8VaHDkPjnOcqdzi8eCe25JEWx5YIqFPy/qjNGwjeuM5JwLzLq1ycs/YWobUOfiSYl1QpVnxNIrpGAWkLGBaxz3YIXFlxRrY1KR8SzvjNonU7xor6Sh12oKLKIgT6TuZwk8ezi4TmSUkwEq/cGcEhuVaFFbnHR44g/hFiWWeZs4iMB2squ1y2JxARUZX56NMR8RWI53K5L7hopDLA1EtYTteCE+NA8NgpS02w/BFvDQSF7Z9WISr6cWKTqAYt/zJdDbklJ4AHm9ofQGSobhwRGMfJU3r675aA7uCCiZ/G6+B/nh/n7weqlcE5VA+hfSVor5uBDZBJBjy//nDVDaIXszfRxF0PmAUpHWRuBmiUp2GqtpR2Cwz/kGmLw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 18.07.23 10:26, Vivek Kasireddy wrote: > A user or admin can configure a VMM (Qemu) Guest's memory to be > backed by hugetlb pages for various reasons. However, a Guest OS > would still allocate (and pin) buffers that are backed by regular > 4k sized pages. In order to map these buffers and create dma-bufs > for them on the Host, we first need to find the hugetlb pages where > the buffer allocations are located and then determine the offsets > of individual chunks (within those pages) and use this information > to eventually populate a scatterlist. > > Testcase: default_hugepagesz=2M hugepagesz=2M hugepages=2500 options > were passed to the Host kernel and Qemu was launched with these > relevant options: qemu-system-x86_64 -m 4096m.... > -device virtio-gpu-pci,max_outputs=1,blob=true,xres=1920,yres=1080 > -display gtk,gl=on > -object memory-backend-memfd,hugetlb=on,id=mem1,size=4096M > -machine memory-backend=mem1 > > Replacing -display gtk,gl=on with -display gtk,gl=off above would > exercise the mmap handler. > > v2: Updated get_sg_table() to manually populate the scatterlist for > both huge page and non-huge-page cases. > > Cc: David Hildenbrand > Cc: Mike Kravetz > Cc: Hugh Dickins > Cc: Peter Xu > Cc: Jason Gunthorpe > Cc: Gerd Hoffmann > Cc: Dongwon Kim > Cc: Junxiao Chang > Signed-off-by: Vivek Kasireddy > --- > drivers/dma-buf/udmabuf.c | 84 +++++++++++++++++++++++++++++++++------ > 1 file changed, 71 insertions(+), 13 deletions(-) LGTM, in general. But I really hope Mike can comment. -- Cheers, David / dhildenb