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[2003:cb:c70a:7e00:bb5b:b526:5b76:5824]) by smtp.gmail.com with ESMTPSA id h4-20020a5d6e04000000b0020d02262664sm5229194wrz.25.2022.06.17.10.33.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jun 2022 10:33:13 -0700 (PDT) Message-ID: <7605beee-0a76-4ee9-e950-17419630f2cf@redhat.com> Date: Fri, 17 Jun 2022 19:33:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH v5 01/13] mm: add zone device coherent type memory support To: "Sierra Guiza, Alejandro (Alex)" , 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> From: David Hildenbrand Organization: Red Hat In-Reply-To: <02ed2cb7-3ad3-8ffc-6032-04ae1853e234@amd.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MH90flJX; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf04.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655487198; 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=l9t8ci2pOVMm92hWEf9qj7OSOv7zoUPsj9UgV8OEIRA=; b=jZbxwp7l4gCNnf9V5J0IjQPYx8lwCy9RXc2JSHRn1YuBnjGej+AHCpFvmzde7rTDDUt+Je pkSPCv4nJLERis1tBRw2TBPh62Hf2AP28BGK0o4GNEm4TPk8B7RslqGZfVI9jjZX+17TWH p6jxVZ2Nl9tdIDBZcv8P5zvt6GIaiWs= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655487198; a=rsa-sha256; cv=none; b=z2cpdeublrumPLBjdnnkvedsfHgWQRuhnVykoOIDaE8whk4w0y6bZIjZy/zwABrhkyv5Lj TnCnbSh1Kp4xYnJs2IdWEsBtPlbafwpydpdL2C1dMDPrq86EP2iIYctR9vBy8PTKRKOGgo o9gxx75OhU73R3I+QVlbjjJGejHYROs= X-Stat-Signature: ahzjirsunpnghr15m65ems79jkjacwto X-Rspamd-Queue-Id: A8EF940092 X-Rspam-User: Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MH90flJX; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf04.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam10 X-HE-Tag: 1655487197-382724 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 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. So wouldn't try_grab_folio() simply pin these pages? What am I missing? -- Thanks, David / dhildenb