From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E690C282DE for ; Mon, 10 Mar 2025 10:23:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 753A6280002; Mon, 10 Mar 2025 06:23:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7027F280001; Mon, 10 Mar 2025 06:23:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5CBBA280002; Mon, 10 Mar 2025 06:23:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 40625280001 for ; Mon, 10 Mar 2025 06:23:53 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id BAB3BC0D1C for ; Mon, 10 Mar 2025 10:23:53 +0000 (UTC) X-FDA: 83205255546.22.C6F601A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf14.hostedemail.com (Postfix) with ESMTP id 41D9010000B for ; Mon, 10 Mar 2025 10:23:51 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=PGePVzJG; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf14.hostedemail.com: domain of jfalempe@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=jfalempe@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1741602231; 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=/12pVfGrHfAC9KyGDgoRmy2bzHmGQuVzoa458sMOedg=; b=uPOHeQvsAzd1zrQiyM03CP13lTNSXAe+bFT9WKoOc2DLxqUhFMhlTQb9kvOi/E6oSxaQKj kov3QLSunTgMY3GVBi0ZPzAriGu1cs5k0IDyzbXc+m3YN5geFucIUXMzL+nMEJEQRasE6z 5l9ddjHmhWOdnd2SksEzbeyjkQQrJ6k= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1741602231; a=rsa-sha256; cv=none; b=5Xb2DXGOHXNBR/ciqrXXbcO6tPGDUuLofhqJE4zqHShoaJylSkr+S/QfY841pMD3YbR1m1 BnBp0wkhGXx5L+aOQWH8cNsxVVEoWeLooJcbSVHIn8DzM0pPdGLy5MPkMRjD8kjnI5Ry/i PROwrvxfaNsFxs4MycerXrZ7AvqojSk= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=PGePVzJG; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf14.hostedemail.com: domain of jfalempe@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=jfalempe@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741602230; h=from:from: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; bh=/12pVfGrHfAC9KyGDgoRmy2bzHmGQuVzoa458sMOedg=; b=PGePVzJGA9AFXWShebGXObQLbomqOe73qMYQlo7e21WiszY5nnn/kOTFVQx4NUYmZjiE7f 725LZV4IseSIMGgmWQSYep3zgZav6i9gEF2xUkUI6mKsWh8nuDGTOtOBK3E+ys000pM2cp oUZl8z4nUc+qME9N0nxU3dD/JMpo1Xw= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-450-Trztt5eDMEm6qFRYehmFEw-1; Mon, 10 Mar 2025 06:23:49 -0400 X-MC-Unique: Trztt5eDMEm6qFRYehmFEw-1 X-Mimecast-MFC-AGG-ID: Trztt5eDMEm6qFRYehmFEw_1741602228 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-3912d5f6689so2509967f8f.1 for ; Mon, 10 Mar 2025 03:23:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1741602228; x=1742207028; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/12pVfGrHfAC9KyGDgoRmy2bzHmGQuVzoa458sMOedg=; b=OH6bXwgFR6ugC/SqorZ4+xIgU2dsg2aydkH+75pMJ1lBw/J/jwFhKbHav7szuia0YZ /kC4cxvu+9v1Tjy83Spx9mdlQfPRV2leQ0a/iyQeEKvneCUQw1JU82vYSHzqYAu8EF7a N1RynIhD6Jj6cAosZbXmCeYA0swT5YZzQK6z3g2GnywCdgDZqHPSkDY2HYPK2f983Non dRQZpo9IKH6nlTafHy3SbbmS8vBCqnlS33CrfJf91I4aA+kknc12TQ2vTscBqnoXhBeE okYYd4eYXJDUrr/QsvJ0gbMj9BzzbDtsBZzHgrqR+4Xf2I/OxR6xxFmp9YFJS9pdePgu FzTw== X-Forwarded-Encrypted: i=1; AJvYcCWatSJV9YWpAl/x6b/hk7lhuXIY+KcL7Dy2aHmQ9RAR8QCVDN799LzRW4xn6F3Xh5eCrQPuQw4tDw==@kvack.org X-Gm-Message-State: AOJu0YyNmq5nEJpkjVw3cpOYUuJ1NUUTpS0XjcN0y9vCQ5DbMo1+uI88 mDEZQeLGYguKkrwgeJ9anJhHUlodU8RVsTbxmPpJOa9DkDigfRSW6iaLf4rA1lyYoC9s+dxij70 cZQQWTzE30LfGePFT0pkKr5dhxUbougjlU6pKSZF37NNJebOi X-Gm-Gg: ASbGncvWWB1IhbAuhPVMDN/65P1MXLPNwaSXVD7Lhx/+nyujxwaagZEuqm3Vq+tLsLK biyxlqG+gTC8pguekKK0rrceqEO0bDcK2Vw1ju0QGF3w1BWf9aW10wiXTcK0tidPf0pvrBOuPJH 3wXu0S/zXW1aGVQz7fJxbizU3cVfB1LUPcmxg1K2D1bFGeaNIpKMGZKJe/G2g4lSJCbKbQk9W18 R5lM/hLcIXWSfDnDz+ixcysyG00qJlnloSmj5UJXs/0TUY54t7ak1PLYz9eYVdwKiigQ1LNqOJT vUTt951ScKDRgMI7Z6k+p4tmRe0Os8uhGfFIhECBT8k6ruJUAQDHjIk= X-Received: by 2002:adf:e007:0:b0:390:f4f9:8396 with SMTP id ffacd0b85a97d-39132d7ff8bmr4952019f8f.28.1741602227909; Mon, 10 Mar 2025 03:23:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGTlUKdfWg/n6nLhAEk75JdM460Sx5llLCeap2DgVS7ohzTSeVMGhEWCd6FidoOs3NkTtglMA== X-Received: by 2002:adf:e007:0:b0:390:f4f9:8396 with SMTP id ffacd0b85a97d-39132d7ff8bmr4951998f8f.28.1741602227497; Mon, 10 Mar 2025 03:23:47 -0700 (PDT) Received: from ?IPV6:2a01:e0a:c:37e0:ced3:55bd:f454:e722? ([2a01:e0a:c:37e0:ced3:55bd:f454:e722]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3912bfdff72sm14634492f8f.36.2025.03.10.03.23.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Mar 2025 03:23:46 -0700 (PDT) Message-ID: Date: Mon, 10 Mar 2025 11:23:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH drm-next 1/2] vmalloc: Add atomic_vmap To: Ryosuke Yasuoka Cc: Matthew Wilcox , maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, kraxel@redhat.com, gurchetansingh@chromium.org, olvaffe@gmail.com, akpm@linux-foundation.org, urezki@gmail.com, hch@infradead.org, dmitry.osipenko@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org References: <20250305152555.318159-1-ryasuoka@redhat.com> <20250305152555.318159-2-ryasuoka@redhat.com> <3bfd4238-6954-41a3-a5a3-8515a3ac9dce@redhat.com> <51c11147-4927-4ebc-9737-fd1eebe4e0bd@redhat.com> From: Jocelyn Falempe In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: t0fbHORibggkr-4EtJKVe5lNlkf655OiPwzvI1baxk0_1741602228 X-Mimecast-Originator: redhat.com Content-Language: en-US, fr Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: zn7h9583dfqhqj76rbxqfs6bu47z1smo X-Rspamd-Server: rspam05 X-Rspam-User: X-Rspamd-Queue-Id: 41D9010000B X-HE-Tag: 1741602231-408138 X-HE-Meta: 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 j46at19W 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 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: List-Subscribe: List-Unsubscribe: On 09/03/2025 09:07, Ryosuke Yasuoka wrote: > On Fri, Mar 7, 2025 at 4:55 PM Jocelyn Falempe wrote: >> >> On 06/03/2025 16:52, Simona Vetter wrote: >>> On Thu, Mar 06, 2025 at 02:24:51PM +0100, Jocelyn Falempe wrote: >>>> On 06/03/2025 05:52, Matthew Wilcox wrote: >>>>> On Thu, Mar 06, 2025 at 12:25:53AM +0900, Ryosuke Yasuoka wrote: >>>>>> Some drivers can use vmap in drm_panic, however, vmap is sleepable and >>>>>> takes locks. Since drm_panic will vmap in panic handler, atomic_vmap >>>>>> requests pages with GFP_ATOMIC and maps KVA without locks and sleep. >>>>> >>>>> In addition to the implicit GFP_KERNEL allocations Vlad mentioned, how >>>>> is this supposed to work? >>>>> >>>>>> + vn = addr_to_node(va->va_start); >>>>>> + >>>>>> + insert_vmap_area(va, &vn->busy.root, &vn->busy.head); >>>>> >>>>> If someone else is holding the vn->busy.lock because they're modifying the >>>>> busy tree, you'll corrupt the tree. You can't just say "I can't take a >>>>> lock here, so I won't bother". You need to figure out how to do something >>>>> safe without taking the lock. For example, you could preallocate the >>>>> page tables and reserve a vmap area when the driver loads that would >>>>> then be usable for the panic situation. I don't know that we have APIs >>>>> to let you do that today, but it's something that could be added. >>>>> >>>> Regarding the lock, it should be possible to use the trylock() variant, and >>>> fail if the lock is already taken. (In the panic handler, only 1 CPU remain >>>> active, so it's unlikely the lock would be released anyway). >>>> >>>> If we need to pre-allocate the page table and reserve the vmap area, maybe >>>> it would be easier to just always vmap() the primary framebuffer, so it can >>>> be used in the panic handler? >>> >>> Yeah I really don't like the idea of creating some really brittle one-off >>> core mm code just so we don't have to vmap a buffer unconditionally. I >>> think even better would be if drm_panic can cope with non-linear buffers, >>> it's entirely fine if the drawing function absolutely crawls and sets each >>> individual byte ... >> >> It already supports some non-linear buffer, like Nvidia block-linear: >> https://elixir.bootlin.com/linux/v6.13.5/source/drivers/gpu/drm/nouveau/dispnv50/wndw.c#L606 >> >> And I've also sent some patches to support Intel's 4-tile and Y-tile format: >> https://patchwork.freedesktop.org/patch/637200/?series=141936&rev=5 >> https://patchwork.freedesktop.org/patch/637202/?series=141936&rev=5 >> >> Hopefully Color Compression can be disabled on intel's GPU, otherwise >> that would be a bit harder to implement than tiling. >> >>> >>> The only thing you're allowed to do in panic is try_lock on a raw spinlock >>> (plus some really scare lockless tricks), imposing that on core mm sounds >>> like a non-starter to me. >>> >>> Cheers, Sima >> > > Thank you all for your comments. > I understand adding atomic_vmap is not possible as vmalloc is not compatible > with GFP_ATOMIC. I'll re-implement this by pre-allocating the page table and > reserve the vmap area while the kernel is alive. It'll might be > allocated in driver > codes so maybe I don't need to add any features in core mm code. Maybe another way to do that, would be to atomically kmap only one page at a time. And when drawing the panic screen, make sure that for each pixel the right page is mapped. Would kmap_local_page() fit for this purpose? Best regards, -- Jocelyn > > Best regards, > Ryosuke >