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[2003:cb:c723:4c00:5c85:5575:c321:cea3]) by smtp.gmail.com with ESMTPSA id i15-20020adffdcf000000b003145559a691sm13875824wrs.41.2023.07.31.12.22.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 31 Jul 2023 12:22:27 -0700 (PDT) Message-ID: <9a26ce23-9ac7-b111-b700-db0905203c73@redhat.com> Date: Mon, 31 Jul 2023 21:22:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 To: Linus Torvalds Cc: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Andrew Morton , liubo , Matthew Wilcox , Hugh Dickins , Jason Gunthorpe , John Hubbard , Mel Gorman References: <20230727212845.135673-1-david@redhat.com> <412bb30f-0417-802c-3fc4-a4e9d5891c5d@redhat.com> <66e26ad5-982e-fe2a-e4cd-de0e552da0ca@redhat.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v1 0/4] smaps / mm/gup: fix gup_can_follow_protnone fallout In-Reply-To: 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-Rspamd-Queue-Id: 13559A0020 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: oargfmmb4161ne9azwafkytqbnihwz3a X-HE-Tag: 1690831351-524475 X-HE-Meta: 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 lymDWzVv sza/LdkF6obw7lnfUZkRWEusPrMlGBt+uYR0X6WpR97yFaHPdn2/XUALmXGREQ2ic/oq+slWVNWOnsfa5D18F0BuUfSoEK8kZULlFfZ0YR+Ey/DkHuLbF9bUhHqzmGyESOPURtaoGxfGpA5LI7pRaWTTo2TsY6IKbfNuuKoSJmRFhHPLOTQO+iyOcicOPfNMsmgcO9otIvQaT7KayLUTmfwUEsJJoLyPkOQiZWoRmXDBcXpKmcZeJPKSI+j1kFHOTj71RokySH5FIV9SVOL0eeVAwGu2tVtcrWW+4cgetbdVxGg78tm+HfiaENGpkV87pLodfomhgkeTsR1Z+dKYvrX5OlhnECvB8ucR/hC1a03HglvVjqYuAqBItkN1fMKT4KWup+GB/f+qDpVFUV9wOHfDxxLS7S/Cx2sEPJ7VUWqowAg+22F+t2kV7IQyAdg4o4FdGV7ZJyMTY10aQA5+v5NzxP6H3VgeZRwaq 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 31.07.23 21:07, Linus Torvalds wrote: > On Mon, 31 Jul 2023 at 12:00, David Hildenbrand wrote: >> >> So in the "!writable" case, we would always call >> get_user_pages_unlocked() and never honor NUMA faults. > > Ok, so kvm doesn't just use the fast version. Oh well. It was an idea.. Certainly an interesting one, thanks for thinking about possible alternatives! Unfortunately, KVM is an advanced GUP user to managed secondary MMUs. I'll get the FOLL_HONOR_NUMA_FAULT patches ready tomorrow and we can discuss if that looks better. (btw, the whole reasoning about "HW would refuse to use these pages" was exactly the whole reason I went into the FOLL_FORCE direction ... but it's really better to make FOLL_FORCE deal with VMA protection only) -- Cheers, David / dhildenb