From c4b5e4bc8317ccb0a822429d87288d9f90453a04 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Tue, 13 Apr 2021 21:08:39 +0300 Subject: [PATCH 4/8] x86/setup: Move trim_snb_memory() later in setup_arch() to fix boot hangs Commit a799c2bd29d1 ("x86/setup: Consolidate early memory reservations") moved reservation of the memory inaccessible by Sandy Bride integrated graphics very early, and, as a result, on systems with such devices the first 1M was reserved by trim_snb_memory() which prevented the allocation of the real mode trampoline and made the boot hang very early. Since the purpose of trim_snb_memory() is to prevent problematic pages ever reaching the graphics device, it is safe to reserve these pages after memblock allocations are possible. Move trim_snb_memory() later in boot so that it will be called after reserve_real_mode() and make comments describing trim_snb_memory() operation more elaborate. [ bp: Massage a bit. ] Fixes: a799c2bd29d1 ("x86/setup: Consolidate early memory reservations") Reported-by: Randy Dunlap Signed-off-by: Mike Rapoport Signed-off-by: Borislav Petkov Tested-by: Randy Dunlap Tested-by: Hugh Dickins Link: https://lkml.kernel.org/r/f67d3e03-af90-f790-baf4-8d412fe055af@infradead.org --- arch/x86/kernel/setup.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 282d572e49af..7d466f51be1f 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -634,11 +634,16 @@ static void __init trim_snb_memory(void) printk(KERN_DEBUG "reserving inaccessible SNB gfx pages\n"); /* - * Reserve all memory below the 1 MB mark that has not - * already been reserved. + * SandyBridge integrated graphics devices have a bug that prevents + * them from accessing certain memory ranges, namely anything below + * 1M and in the pages listed in bad_pages[] above. + * + * To avoid these pages being ever accessed by SNB gfx devices + * reserve all memory below the 1 MB mark and bad_pages that have + * not already been reserved at boot time. */ memblock_reserve(0, 1<<20); - + for (i = 0; i < ARRAY_SIZE(bad_pages); i++) { if (memblock_reserve(bad_pages[i], PAGE_SIZE)) printk(KERN_WARNING "failed to reserve 0x%08lx\n", @@ -747,8 +752,6 @@ static void __init early_reserve_memory(void) reserve_ibft_region(); reserve_bios_regions(); - - trim_snb_memory(); } /* @@ -1082,6 +1085,13 @@ void __init setup_arch(char **cmdline_p) reserve_real_mode(); + /* + * Reserving memory causing GPU hangs on Sandy Bridge integrated + * graphics devices should be done after we allocated memory under + * 1M for the real mode trampoline. + */ + trim_snb_memory(); + init_mem_mapping(); idt_setup_early_pf(); -- 2.32.0