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dkim=pass header.d=amd.com header.s=selector1 header.b=cJ2rCU3P; spf=pass (imf19.hostedemail.com: domain of Felix.Kuehling@amd.com designates 40.107.220.65 as permitted sender) smtp.mailfrom=Felix.Kuehling@amd.com; dmarc=pass (policy=quarantine) header.from=amd.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 63EC890009E8 X-Stat-Signature: i51xqjk7qceuankqnrfansskuuuszgjq X-HE-Tag: 1624485001-248459 Content-Transfer-Encoding: quoted-printable 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 2021-06-20 10:14 a.m., Theodore Ts'o wrote: > On Thu, Jun 17, 2021 at 10:16:57AM -0500, Alex Sierra wrote: >> v1: >> AMD is building a system architecture for the Frontier supercomputer w= ith a >> coherent interconnect between CPUs and GPUs. This hardware architectur= e allows >> the CPUs to coherently access GPU device memory. We have hardware in o= ur labs >> and we are working with our partner HPE on the BIOS, firmware and soft= ware >> for delivery to the DOE. >> >> The system BIOS advertises the GPU device memory (aka VRAM) as SPM >> (special purpose memory) in the UEFI system address map. The amdgpu dr= iver looks >> it up with lookup_resource and registers it with devmap as MEMORY_DEVI= CE_GENERIC >> using devm_memremap_pages. >> >> Now we're trying to migrate data to and from that memory using the mig= rate_vma_* >> helpers so we can support page-based migration in our unified memory a= llocations, >> while also supporting CPU access to those pages. >> >> This patch series makes a few changes to make MEMORY_DEVICE_GENERIC pa= ges behave >> correctly in the migrate_vma_* helpers. We are looking for feedback ab= out this >> approach. If we're close, what's needed to make our patches acceptable= upstream? >> If we're not close, any suggestions how else to achieve what we are tr= ying to do >> (i.e. page migration and coherent CPU access to VRAM)? > Is there a way we can test the codepaths touched by this patchset? It > doesn't have to be via a complete qemu simulation of the GPU device > memory, but some way of creating MEMORY_DEVICE_GENERIC subject to > migrate_vma_* helpers so we can test for regressions moving forward. Hi Theodore, I can think of two ways to test the changes for MEMORY_DEVICE_GENERIC in=20 this patch series in a way that is reproducible without special hardware=20 and firmware: For the reference counting changes we could use the dax driver with hmem=20 and use efi_fake_mem on the kernel command line to create some=20 DEVICE_GENERIC pages. I'm open to suggestions for good user mode tests=20 to exercise dax functionality on this type of memory. For the migration helper changes we could modify or parametrize=20 lib/hmm_test.c to create DEVICE_GENERIC pages instead of DEVICE_PRIVATE.=20 Then run tools/testing/selftests/vm/hmm-tests.c. Regards, =C2=A0 Felix > > Thanks, > > - Ted