Commit c361e5d4 authored Apr 13, 2021 by Mike Rapoport Committed by Borislav Petkov Apr 14, 2021

x86/setup: Move trim_snb_memory() later in setup_arch() to fix boot hangs



Commit

  a799c2bd ("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: a799c2bd ("x86/setup: Consolidate early memory reservations")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Hugh Dickins <hughd@google.com>
Link: https://lkml.kernel.org/r/f67d3e03-af90-f790-baf4-8d412fe055af@infradead.org

parent 4c674481

arch/x86/kernel/setup.c

+15 −5

Original line number	Diff line number	Diff line
		@@ -633,8 +633,13 @@ 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);

		@@ -746,8 +751,6 @@ static void __init early_reserve_memory(void)

		reserve_ibft_region();
		reserve_bios_regions();

		trim_snb_memory();
		}

		/*
		@@ -1081,6 +1084,13 @@ 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();