Commit 5ff3e2c3 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

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



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: default avatarAndy 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: default avatarIngo Molnar <mingo@kernel.org>
parent d0de0f68

arch/x86/include/asm/realmode.h

+9 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/realmode/init.c

+21 −8
Original line number Diff line number Diff line 
#include <linux/io.h>

#include <linux/slab.h>

#include <linux/memblock.h>



#include <asm/cacheflush.h>
@@ -12,22 +13,34 @@ u32 *trampoline_cr4_features; 
/* Hold the pgd entry used on booting additional CPUs */

pgd_t trampoline_pgd_entry;



void __init set_real_mode_mem(phys_addr_t mem, size_t size)

{

	void *base = __va(mem);



	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;

	unsigned char *base;

	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);

	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)

		panic("Cannot allocate trampoline\n");

	if (!mem) {

		pr_info("No sub-1M memory is available for the trampoline\n");

		return;

	}



	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);

	set_real_mode_mem(mem, size);

}



static void __init setup_real_mode(void)

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