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Fri, 17 Jun 2022 19:27:48 +0000 Received: from SN6PR12MB2717.namprd12.prod.outlook.com ([fe80::b9a8:66b3:9ed6:2db]) by SN6PR12MB2717.namprd12.prod.outlook.com ([fe80::b9a8:66b3:9ed6:2db%5]) with mapi id 15.20.5353.015; Fri, 17 Jun 2022 19:27:48 +0000 Message-ID: Date: Fri, 17 Jun 2022 14:27:43 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v5 01/13] mm: add zone device coherent type memory support Content-Language: en-US To: David Hildenbrand , jgg@nvidia.com Cc: Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jglisse@redhat.com, apopple@nvidia.com, willy@infradead.org, akpm@linux-foundation.org References: <20220531200041.24904-1-alex.sierra@amd.com> <20220531200041.24904-2-alex.sierra@amd.com> <3ac89358-2ce0-7d0d-8b9c-8b0e5cc48945@redhat.com> <02ed2cb7-3ad3-8ffc-6032-04ae1853e234@amd.com> <7605beee-0a76-4ee9-e950-17419630f2cf@redhat.com> From: "Sierra Guiza, Alejandro (Alex)" In-Reply-To: <7605beee-0a76-4ee9-e950-17419630f2cf@redhat.com> Content-Type: text/plain; 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imf21.hostedemail.com; dkim=pass header.d=amd.com header.s=selector1 header.b=kagjKiJr; dmarc=pass (policy=quarantine) header.from=amd.com; spf=pass (imf21.hostedemail.com: domain of Alex.Sierra@amd.com designates 40.107.223.71 as permitted sender) smtp.mailfrom=Alex.Sierra@amd.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655494070; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4A54WpO8Or7yFvdqAJK3w9VlcZlbDxJd5nnTE7n1vYs=; b=3fpbYjxYg3HxutEkl92Fs6laZZYgLS3oLF/0di8nqulhYIikuAvgUjl4mDAlq/Mls3YCGe 1z6KYB7La/7/4BjzfPORZu/XJT0BhzA/mCvXBeCIPeMLTkYu0T4QO2QfLRQVu5lXbTS0S5 PTHefL2M3J/s4/QLn6bRn352lpgh0NQ= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1655494070; a=rsa-sha256; cv=pass; b=ICHvEhJanaoDdzjEZNUcsl4xvUk2MsUcnuKc1AcJcV2AnorWtbIdFjIuhKaPYSx2uOPlwi EkPJu8OyAiN0+xSlnBJ3zxSBOF3w9NqSgZR4h/XKi72XpQ3Ev3MGKvMhkadOnMWn1eGKsk xLjo5adUIaTyOxg9H+DpH1CoPvnlrXk= X-Stat-Signature: afmduppw6qpbsed4pczn69ti715bbq5z X-Rspamd-Queue-Id: 8E5681C00A8 X-Rspam-User: Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=amd.com header.s=selector1 header.b=kagjKiJr; dmarc=pass (policy=quarantine) header.from=amd.com; spf=pass (imf21.hostedemail.com: domain of Alex.Sierra@amd.com designates 40.107.223.71 as permitted sender) smtp.mailfrom=Alex.Sierra@amd.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Rspamd-Server: rspam10 X-HE-Tag: 1655494070-148590 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 6/17/2022 12:33 PM, David Hildenbrand wrote: > On 17.06.22 19:20, Sierra Guiza, Alejandro (Alex) wrote: >> On 6/17/2022 4:40 AM, David Hildenbrand wrote: >>> On 31.05.22 22:00, Alex Sierra wrote: >>>> Device memory that is cache coherent from device and CPU point of view. >>>> This is used on platforms that have an advanced system bus (like CAPI >>>> or CXL). Any page of a process can be migrated to such memory. However, >>>> no one should be allowed to pin such memory so that it can always be >>>> evicted. >>>> >>>> Signed-off-by: Alex Sierra >>>> Acked-by: Felix Kuehling >>>> Reviewed-by: Alistair Popple >>>> [hch: rebased ontop of the refcount changes, >>>> removed is_dev_private_or_coherent_page] >>>> Signed-off-by: Christoph Hellwig >>>> --- >>>> include/linux/memremap.h | 19 +++++++++++++++++++ >>>> mm/memcontrol.c | 7 ++++--- >>>> mm/memory-failure.c | 8 ++++++-- >>>> mm/memremap.c | 10 ++++++++++ >>>> mm/migrate_device.c | 16 +++++++--------- >>>> mm/rmap.c | 5 +++-- >>>> 6 files changed, 49 insertions(+), 16 deletions(-) >>>> >>>> diff --git a/include/linux/memremap.h b/include/linux/memremap.h >>>> index 8af304f6b504..9f752ebed613 100644 >>>> --- a/include/linux/memremap.h >>>> +++ b/include/linux/memremap.h >>>> @@ -41,6 +41,13 @@ struct vmem_altmap { >>>> * A more complete discussion of unaddressable memory may be found in >>>> * include/linux/hmm.h and Documentation/vm/hmm.rst. >>>> * >>>> + * MEMORY_DEVICE_COHERENT: >>>> + * Device memory that is cache coherent from device and CPU point of view. This >>>> + * is used on platforms that have an advanced system bus (like CAPI or CXL). A >>>> + * driver can hotplug the device memory using ZONE_DEVICE and with that memory >>>> + * type. Any page of a process can be migrated to such memory. However no one >>> Any page might not be right, I'm pretty sure. ... just thinking about special pages >>> like vdso, shared zeropage, ... pinned pages ... > Well, you cannot migrate long term pages, that's what I meant :) > >>>> + * should be allowed to pin such memory so that it can always be evicted. >>>> + * >>>> * MEMORY_DEVICE_FS_DAX: >>>> * Host memory that has similar access semantics as System RAM i.e. DMA >>>> * coherent and supports page pinning. In support of coordinating page >>>> @@ -61,6 +68,7 @@ struct vmem_altmap { >>>> enum memory_type { >>>> /* 0 is reserved to catch uninitialized type fields */ >>>> MEMORY_DEVICE_PRIVATE = 1, >>>> + MEMORY_DEVICE_COHERENT, >>>> MEMORY_DEVICE_FS_DAX, >>>> MEMORY_DEVICE_GENERIC, >>>> MEMORY_DEVICE_PCI_P2PDMA, >>>> @@ -143,6 +151,17 @@ static inline bool folio_is_device_private(const struct folio *folio) >>> In general, this LGTM, and it should be correct with PageAnonExclusive I think. >>> >>> >>> However, where exactly is pinning forbidden? >> Long-term pinning is forbidden since it would interfere with the device >> memory manager owning the >> device-coherent pages (e.g. evictions in TTM). However, normal pinning >> is allowed on this device type. > I don't see updates to folio_is_pinnable() in this patch. Device coherent type pages should return true here, as they are pinnable pages. > > So wouldn't try_grab_folio() simply pin these pages? What am I missing? As far as I understand this return NULL for long term pin pages. Otherwise they get refcount incremented. Regards, Alex Sierra >