Trying VMAP_STACK with KVM, vmlinux was not starting. This was due to SRR0 and SRR1 clobbered by an ISI due to the rfi being in a different page than the mtsrr0/1: c0003fe0 <mmu_off>: c0003fe0: 38 83 00 54 addi r4,r3,84 c0003fe4: 7c 60 00 a6 mfmsr r3 c0003fe8: 70 60 00 30 andi. r0,r3,48 c0003fec: 4d 82 00 20 beqlr c0003ff0: 7c 63 00 78 andc r3,r3,r0 c0003ff4: 7c 9a 03 a6 mtsrr0 r4 c0003ff8: 7c 7b 03 a6 mtsrr1 r3 c0003ffc: 7c 00 04 ac hwsync c0004000: 4c 00 00 64 rfi Align the 4 instruction block used to deactivate MMU to order 4, so that the block never crosses a page boundary. Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx> --- arch/powerpc/kernel/head_32.S | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S index 7ec780858299..90ef355e958b 100644 --- a/arch/powerpc/kernel/head_32.S +++ b/arch/powerpc/kernel/head_32.S @@ -917,6 +917,8 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_HPTE_TABLE) ori r4,r4,2f@l tophys(r4,r4) li r3,MSR_KERNEL & ~(MSR_IR|MSR_DR) + + .align 4 mtspr SPRN_SRR0,r4 mtspr SPRN_SRR1,r3 SYNC @@ -1058,6 +1060,8 @@ _ENTRY(update_bats) rlwinm r0, r6, 0, ~MSR_RI rlwinm r0, r0, 0, ~MSR_EE mtmsr r0 + + .align 4 mtspr SPRN_SRR0, r4 mtspr SPRN_SRR1, r3 SYNC @@ -1097,6 +1101,8 @@ mmu_off: andi. r0,r3,MSR_DR|MSR_IR /* MMU enabled? */ beqlr andc r3,r3,r0 + + .align 4 mtspr SPRN_SRR0,r4 mtspr SPRN_SRR1,r3 sync -- 2.13.3
