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From c4b5e4bc8317ccb0a822429d87288d9f90453a04 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.ibm.com>
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 <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
---
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
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