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x86/boot: Rework reserve_real_mode() to allow multiple tries

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If reserve_real_mode() fails, panicing immediately means we're
doomed.  Make it safe to try more than once to allocate the
trampoline:

 - Degrade a failure from panic() to pr_info().  (If we make it to
   setup_real_mode() without reserving the trampoline, we'll panic
   them.)

 - Factor out helpers so that platform code can supply a specific
   address to try.

 - Warn if reserve_real_mode() is called after we're done with the
   memblock allocator.  If that were to happen, we would behave
   unpredictably.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Matt Fleming <mfleming@suse.de>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/876e383038f3e9971aa72fd20a4f5da05f9d193d.1470821230.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2016-08-10 02:29:16 -07:00 committed by Ingo Molnar
parent d0de0f685d
commit 5ff3e2c3c3
2 changed files with 33 additions and 11 deletions
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9
arch/x86/include/asm/realmode.h
View File

@ -58,6 +58,15 @@ extern unsigned char boot_gdt[];
extern unsigned char secondary_startup_64[];
#endif
static inline size_t real_mode_size_needed(void)
{
if (real_mode_header)
return 0; /* already allocated. */
return ALIGN(real_mode_blob_end - real_mode_blob, PAGE_SIZE);
}
void set_real_mode_mem(phys_addr_t mem, size_t size);
void reserve_real_mode(void);
#endif /* _ARCH_X86_REALMODE_H */

35
arch/x86/realmode/init.c
View File

@ -1,4 +1,5 @@
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/memblock.h>
#include <asm/cacheflush.h>
@ -12,24 +13,36 @@ u32 *trampoline_cr4_features;
/* Hold the pgd entry used on booting additional CPUs */
pgd_t trampoline_pgd_entry;
void __init reserve_real_mode(void)
void __init set_real_mode_mem(phys_addr_t mem, size_t size)
{
phys_addr_t mem;
unsigned char *base;
size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
void *base = __va(mem);
/* Has to be under 1M so we can execute real-mode AP code. */
mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
if (!mem)
panic("Cannot allocate trampoline\n");
base = __va(mem);
memblock_reserve(mem, size);
real_mode_header = (struct real_mode_header *) base;
printk(KERN_DEBUG "Base memory trampoline at [%p] %llx size %zu\n",
base, (unsigned long long)mem, size);
}
void __init reserve_real_mode(void)
{
phys_addr_t mem;
size_t size = real_mode_size_needed();
if (!size)
return;
WARN_ON(slab_is_available());
/* Has to be under 1M so we can execute real-mode AP code. */
mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
if (!mem) {
pr_info("No sub-1M memory is available for the trampoline\n");
return;
}
memblock_reserve(mem, size);
set_real_mode_mem(mem, size);
}
static void __init setup_real_mode(void)
{
u16 real_mode_seg;