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powerpc/64/kexec: Copy image with MMU off when possible

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Currently we turn the MMU off after copying the image, and we make
sure there is no overlap between the hash table and the target pages
in that case.

That doesn't work for Radix however. In that case, the page tables
are scattered and we can't really enforce that the target of the
image isn't overlapping one of them.

So instead, let's turn the MMU off before copying the image in radix
mode. Thankfully, in radix mode, even under a hypervisor, we know we
don't have the same kind of RMA limitations that hash mode has.

While at it, also turn the MMU off early when using hash in non-LPAR
mode, that way we can get rid of the collision check completely.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt
2016-08-19 14:22:38 +05:30
committed by Michael Ellerman
parent be34d30059
commit b970b41ea6
2 changed files with 36 additions and 31 deletions
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18
arch/powerpc/kernel/misc_64.S
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@@ -592,7 +592,8 @@ real_mode: /* assume normal blr return */
#endif
/*
* kexec_sequence(newstack, start, image, control, clear_all())
* kexec_sequence(newstack, start, image, control, clear_all(),
copy_with_mmu_off)
*
* does the grungy work with stack switching and real mode switches
* also does simple calls to other code
@@ -628,7 +629,7 @@ _GLOBAL(kexec_sequence)
mr r29,r5 /* image (virt) */
mr r28,r6 /* control, unused */
mr r27,r7 /* clear_all() fn desc */
mr r26,r8 /* spare */
mr r26,r8 /* copy_with_mmu_off */
lhz r25,PACAHWCPUID(r13) /* get our phys cpu from paca */
/* disable interrupts, we are overwriting kernel data next */
@@ -640,15 +641,24 @@ _GLOBAL(kexec_sequence)
mtmsrd r3,1
#endif
/* We need to turn the MMU off unless we are in hash mode
* under a hypervisor
*/
cmpdi r26,0
beq 1f
bl real_mode
1:
/* copy dest pages, flush whole dest image */
mr r3,r29
bl kexec_copy_flush /* (image) */
/* turn off mmu */
/* turn off mmu now if not done earlier */
cmpdi r26,0
bne 1f
bl real_mode
/* copy 0x100 bytes starting at start to 0 */
li r3,0
1: li r3,0
mr r4,r30 /* start, aka phys mem offset */
li r5,0x100
li r6,0