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Fri, 30 Oct 2026 10:15:16 +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 4e56ATRu5Gp4DgAAD6G6ig (envelope-from ); Fri, 30 Oct 2026 10:15:16 +0000 Message-ID: <5965d410-e011-442c-b564-e1d5e75154cc@suse.de> Date: Fri, 30 Oct 2026 11:15:15 +0100 X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/video: Preserve the default VGA fallback for legacy modes To: Hengyu Liang Cc: x86@kernel.org, bp@alien8.de, mario.limonciello@amd.com, aaron.ma@canonical.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20261029162311.3389523-1-hengyul@cs.unc.edu> <4379fd92-ac4f-45c2-9f4a-eaabe4b7f981@suse.de> <20261030092422.300856-1-hengyul@cs.unc.edu> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-13.29 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-0.999]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:url,imap1.dmz-prg2.suse.org:helo,suse.de:email] X-Spam-Score: -13.29 X-Spam-Level: X-Spam-Flag: NO Hi Am 30.10.26 um 10:24 schrieb Hengyu Liang: > Hi Thomas, > > On Fri, Oct 30, 2026 at 09:48:19AM +0100, Thomas Zimmermann wrote: >> Am 29.10.26 um 17:23 schrieb Hengyu Liang: >>> However, screen_info_resources() also returns legacy I/O and memory >>> ranges for VGA text modes. These ranges are not PCI BARs, so the resource >>> lookup fails and the default VGA fallback is skipped. >> If the BIOS booted in text mode or VGA graphics mode, the rsp device is >> still the primary display device. So the current matching code is not >> necessarily incorrect. (But also not necessarily correct either. :) > I agree that the device is still the primary display in text mode. The > patch gets that from the vga_default_device() fallback, since the legacy > ranges can't be matched against BARs. > >>> diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c >>> index 8ed82fff7638..b8f83346dfe8 100644 >>> --- a/arch/x86/video/video-common.c >>> +++ b/arch/x86/video/video-common.c >>> @@ -45,7 +45,7 @@ bool video_is_primary_device(struct device *dev) >>> >>> #ifdef CONFIG_SCREEN_INFO >>> numres = screen_info_resources(si, res, ARRAY_SIZE(res)); >>> - if (numres > 0) { >>> + if (numres > 0 && __screen_info_has_lfb(screen_info_video_type(si))) { >>> for (i = 0; i < numres; ++i) { >>> if (!(res[i].flags & IORESOURCE_MEM)) >>> continue; >> Further below in that code is a call to pci_find_resource(). [1] Why >> does it match with vkms? Vkms is not even on a PCI device. > It doesn't match vkms. As you say, vkms isn't a PCI device, so > video_is_primary_device() returns false for it at the dev_is_pci() check. > > The problem is on the bochs side. In text mode, screen_info_resources() > returns the legacy VGA ranges, pci_find_resource() doesn't find them in > the BARs, and the function returns false there as well. So no device is > primary, and fbcon stays on the first registered framebuffer. In this > setup that is vkms (fb0), so the console is never remapped to bochs (fb1). I see. That makes sense. Thanks for clarifying. Reviewed-by: Thomas Zimmermann Best regards Thomas > > vkms only makes the console part visible. Without vkms, tty1 has the same > size with and without the patch, but boot_display is still missing without > it. > > Thanks, > Hengyu -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)