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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 762F0221D4 X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-13.50 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; XM_UA_NO_VERSION(0.01)[]; RCVD_TLS_ALL(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MIME_TRACE(0.00)[0:+]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.com:url,suse.de:dkim]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Score: -13.50 Hi Am 29.10.26 um 00:15 schrieb Bjorn Helgaas: > On Wed, Oct 28, 2026 at 05:46:34PM +0800, wuqianhai@loongson.cn wrote: >> From: wuqianhai >> >> PCI resource assignment can relocate the firmware framebuffer BAR, which >> leaves the base address in screen_info stale. The VGA arbiter then calls >> screen_info_pci_dev() from vga_is_firmware_default(), which fails to match >> the framebuffer against any PCI device's BARs. As a result, the boot VGA >> device is not recognized and the arbiter may select the wrong default >> device. >> >> Fix this by calling screen_info_apply_fixups() in vga_arb_device_init() >> before adding the VGA devices. This relocates lfb_base to the assigned >> BAR address so that vga_is_firmware_default() matches the boot device >> again. >> >> Tested on a LoongArch platform, with vga_is_firmware_default() >> additionally enabled for CONFIG_LOONGARCH via local changes. >> >> Fixes: 337bf13aa9ddab8ae47f2677ab75cf69ae33437b ("PCI/VGA: Replace vga_is_firmware_default() with a screen info check") >> Signed-off-by: wuqianhai >> --- >> drivers/pci/vgaarb.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c >> index 3e58b2c05c85..aca594651f58 100644 >> --- a/drivers/pci/vgaarb.c >> +++ b/drivers/pci/vgaarb.c >> @@ -1527,6 +1527,14 @@ static int __init vga_arb_device_init(void) >> int rc; >> struct pci_dev *pdev; >> >> + /* >> + * PCI resource assignment may have relocated the firmware >> + * framebuffer BAR. Update screen_info's lfb_base so that >> + * vga_is_firmware_default() can match it against the boot >> + * device's relocated resource. >> + */ >> + screen_info_apply_fixups(); > I'm really confused about this. vga_is_firmware_default() relies on > screen_info_pci_dev(&sysfb_primary_display.screen): > > vga_is_firmware_default > screen_info_pci_dev(&sysfb_primary_display.screen) > numres = screen_info_resources(&sysfb_primary_display.screen, res, ...) > for (i = 0; i < numres; ++i) > pdev = __screen_info_pci_dev(&res[i]) > > screen_info_resources() returns resource structs with PCI bus > addresses in them. These are not valid CPU addresses, so that seems > broken on any system where bus addresses are not the same as CPU > addresses. What we get from the firmware for the framebuffer is a memory range.   If the underlying PCI memory gets relocated during the boot, we need to update the framebuffer data accordingly. This has worked well for the last 20 yrs. > > screen_info_fixup_lfb() and screen_info_apply_fixups() may fix the > issue you see, but I think the way this happens is questionable. > > screen_info_fixup_lfb() captures the framebuffer PCI bus address in > screen_info_lfb_res_start. Then screen_info_apply_fixups() compares > that PCI bus address with the CPU address in pdev->resource[]. That's > broken on any system where bus addresses are not the same as CPU > addresses. I think it's also broken because screen_info_lfb_res_start > may not be at the beginning of the BAR. > > I think screen_info_fixup_lfb() should only capture the pci_dev, the > BAR number, and the framebuffer offset into the BAR. When we need the > CPU or bus address, we can always compute it from those values. This is not sufficient, I think. We did this until a while ago and got problems with relocated bars. IIRC aarch64 had a number of affected systems. See commit 2f29b5c23101 ("video: screen_info: Relocate framebuffers behind PCI bridges") for details. I'm happy to improve that code though, if we can do something better. Best regards Thomas > >> rc = misc_register(&vga_arb_device); >> if (rc < 0) >> pr_err("error %d registering device\n", rc); >> -- >> 2.34.1 >> -- -- 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)