On some HyperV machines, if kexec_file_load is used to load the kexec kernel, second kernel could hang with following stacktrace: [ 0.591705] efifb: probing for efifb [ 0.596869] efifb: framebuffer at 0xf8000000, using 3072k, total 3072k [ 0.605894] efifb: mode is 1024x768x32, linelength=4096, pages=1 [ 0.617926] efifb: scrolling: redraw [ 0.622715] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 [ 28.039046] watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [swapper/0:1] [ 28.039046] Modules linked in: [ 28.039046] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.18.0-230.el8.x86_64 #1 [ 28.039046] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.0 12/17/2019 [ 28.039046] RIP: 0010:cfb_imageblit+0x450/0x4c0 [ 28.039046] Code: 89 f8 b9 08 00 00 00 48 89 04 24 eb 2d 41 0f be 30 29 e9 4c 8d 5f 04 d3 fe 44 21 ee 41 8b 04 b6 44 21 c8 89 c6 44 31 d6 89 37 <85> c9 75 09 49 83 c0 01 b9 08 00 00 00 4c 89 df 48 39 df 75 ce 83 [ 28.039046] RSP: 0018:ffffc90000087830 EFLAGS: 00010246 ORIG_RAX: ffffffffffffff12 [ 28.039046] RAX: 0000000000000000 RBX: ffffc90000542000 RCX: 0000000000000003 [ 28.039046] RDX: 000000000000000e RSI: 0000000000000000 RDI: ffffc90000541bf0 [ 28.039046] RBP: 0000000000000001 R08: ffff8880f555c8df R09: 0000000000aaaaaa [ 28.039046] R10: 0000000000000000 R11: ffffc90000541bf4 R12: 0000000000001000 [ 28.039046] R13: 0000000000000001 R14: ffffffff81e9a460 R15: ffff8880f555c880 [ 28.039046] FS: 0000000000000000(0000) GS:ffff8880f1000000(0000) knlGS:0000000000000000 [ 28.039046] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.039046] CR2: 00007f7b223b8000 CR3: 00000000f3a0a004 CR4: 00000000003606b0 [ 28.039046] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 28.039046] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 28.039046] Call Trace: [ 28.039046] bit_putcs+0x2a1/0x550 [ 28.039046] ? fbcon_switch+0x33e/0x5b0 [ 28.039046] ? bit_clear+0x120/0x120 [ 28.039046] fbcon_putcs+0xe7/0x100 [ 28.039046] do_update_region+0x154/0x1a0 [ 28.039046] redraw_screen+0x209/0x240 [ 28.039046] ? vc_do_resize+0x5c9/0x660 [ 28.039046] fbcon_prepare_logo+0x3b3/0x430 [ 28.039046] fbcon_init+0x436/0x630 [ 28.039046] visual_init+0xce/0x130 [ 28.039046] do_bind_con_driver+0x1df/0x2d0 [ 28.039046] do_take_over_console+0x113/0x180 [ 28.039046] do_fbcon_takeover+0x58/0xb0 [ 28.039046] register_framebuffer+0x225/0x2f0 [ 28.039046] efifb_probe.cold.5+0x51a/0x55d [ 28.039046] platform_drv_probe+0x38/0x90 [ 28.039046] really_probe+0x212/0x440 [ 28.039046] driver_probe_device+0x49/0xc0 [ 28.039046] device_driver_attach+0x50/0x60 [ 28.039046] __driver_attach+0x61/0x130 [ 28.039046] ? device_driver_attach+0x60/0x60 [ 28.039046] bus_for_each_dev+0x77/0xc0 [ 28.039046] ? klist_add_tail+0x57/0x70 [ 28.039046] bus_add_driver+0x14d/0x1e0 [ 28.039046] ? vesafb_driver_init+0x13/0x13 [ 28.039046] ? do_early_param+0x91/0x91 [ 28.039046] driver_register+0x6b/0xb0 [ 28.039046] ? vesafb_driver_init+0x13/0x13 [ 28.039046] do_one_initcall+0x46/0x1c3 [ 28.039046] ? do_early_param+0x91/0x91 [ 28.039046] kernel_init_freeable+0x1b4/0x25d [ 28.039046] ? rest_init+0xaa/0xaa [ 28.039046] kernel_init+0xa/0xfa [ 28.039046] ret_from_fork+0x35/0x40 The root cause is that hyperv_fb driver will relocate the framebuffer address in first kernel, but kexec_file_load simply reuse the old framebuffer info from boot_params, which is now invalid, so second kernel will write to an invalid framebuffer address. This series fix this problem by: 1. Let kexec_file_load use the updated copy of screen_info. Instead of using boot_params.screen_info, use the globally available screen_info variable instead (which is just an copy of boot_params.screen_info on x86). This variable could be updated by arch indenpendent drivers. Just keep this variable updated should be a good way to keep screen_info consistent across kexec. 2. Let hyperv_fb clean the screen_info copy when the boot framebuffer is relocated outside the old framebuffer. After the relocation, the framebuffer is no longer a VGA framebuffer, so just clean it up should be good. Kairui Song (2): x86/kexec: Use up-to-dated screen_info copy to fill boot params hyperv_fb: Update screen_info after removing old framebuffer arch/x86/kernel/kexec-bzimage64.c | 3 +-- drivers/video/fbdev/hyperv_fb.c | 8 ++++++++ 2 files changed, 9 insertions(+), 2 deletions(-) -- 2.28.0
