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bh=DqlhqDH+e2vFicbuco4eCCmjcNtipVk/C0dg4d70Inc=; b=syc0Mgqr+wgCce7/H3q7Lx8OCxTExO6Z5nJO5Ge04dgb119/BGQANYLHrcRVdijEfTCKNq 0hTZh+bkkKbVu3Dw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 2B4B513A1D; Tue, 3 Jun 2025 06:25:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id f/MgCFWVPmi1egAAD6G6ig (envelope-from ); Tue, 03 Jun 2025 06:25:25 +0000 Message-ID: Date: Tue, 3 Jun 2025 08:25:24 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/4] fbdev/deferred-io: Support contiguous kernel memory framebuffers To: Michael Kelley , David Hildenbrand , "simona@ffwll.ch" , "deller@gmx.de" , "haiyangz@microsoft.com" , "kys@microsoft.com" , "wei.liu@kernel.org" , "decui@microsoft.com" , "akpm@linux-foundation.org" Cc: "weh@microsoft.com" , "hch@lst.de" , "dri-devel@lists.freedesktop.org" , "linux-fbdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-hyperv@vger.kernel.org" , "linux-mm@kvack.org" References: <20250523161522.409504-1-mhklinux@outlook.com> <20250523161522.409504-4-mhklinux@outlook.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Queue-Id: B8B962126A X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: -4.51 Hi Am 03.06.25 um 03:49 schrieb Michael Kelley: [...] >> Will the VMA have VM_PFNMAP or VM_MIXEDMAP set? PFN_SPECIAL is a >> horrible hack. >> >> In another thread, you mention that you use PFN_SPECIAL to bypass the >> check in vm_mixed_ok(), so VM_MIXEDMAP is likely not set? > The VMA has VM_PFNMAP set, not VM_MIXEDMAP. It seemed like > VM_MIXEDMAP is somewhat of a superset of VM_PFNMAP, but maybe that's > a wrong impression. vm_mixed_ok() does a thorough job of validating the > use of __vm_insert_mixed(), and since what I did was allowed, I thought > perhaps it was OK. Your feedback has set me straight, and that's what I > needed. :-) > > But the whole approach is moot with Alistair Popple's patch set that > eliminates pfn_t. Is there an existing mm API that will do mkwrite on a > special PTE in a VM_PFNMAP VMA? I didn't see one, but maybe I missed > it. If there's not one, I'll take a crack at adding it in the next version of my > patch set. What is the motivation behind this work? The driver or fbdev as a whole does not have much of a future anyway. I'd like to suggest removing hyperv_fb entirely in favor of hypervdrm? Best regards Thomas > > Michael -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)