[PATCH v2] poewrpc/mce: Fix SLB rebolting during MCE recovery path.

From: Mahesh Salgaonkar <redacted>

With the powrpc next commit e7e81847478 (poewrpc/mce: Fix SLB rebolting
during MCE recovery path.), the SLB error recovery is broken. The new
change now does not add index value to RB[52-63] that selects the SLB
entry while rebolting, instead it assumes that the shadow save area
already have index embeded correctly in esid field. While all valid bolted
save areas do contain index value set correctly, there is a case where
3rd (KSTACK_INDEX) entry for kernel stack does not embed index for NULL
esid entry. This patch fixes that.

Without this patch the SLB rebolt code overwirtes the 1st entry of kernel
linear mapping and causes SLB recovery to fail.

Signed-off-by: Mahesh Salgaonkar <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/mm/slb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 0b095fa54049..9f574e59d178 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c

@@ -70,7 +70,7 @@ static inline void slb_shadow_update(unsigned long ea, int ssize,
 
 static inline void slb_shadow_clear(enum slb_index index)
 {
-	WRITE_ONCE(get_slb_shadow()->save_area[index].esid, 0);
+	WRITE_ONCE(get_slb_shadow()->save_area[index].esid, cpu_to_be64(index));
 }
 
 static inline void create_shadowed_slbe(unsigned long ea, int ssize,

On 08/23/2018 10:26 AM, Mahesh J Salgaonkar wrote:

From: Mahesh Salgaonkar <redacted>

With the powrpc next commit e7e81847478 (poewrpc/mce: Fix SLB rebolting
during MCE recovery path.), the SLB error recovery is broken. The new
change now does not add index value to RB[52-63] that selects the SLB
entry while rebolting, instead it assumes that the shadow save area
already have index embeded correctly in esid field. While all valid bolted
save areas do contain index value set correctly, there is a case where
3rd (KSTACK_INDEX) entry for kernel stack does not embed index for NULL
esid entry. This patch fixes that.

Without this patch the SLB rebolt code overwirtes the 1st entry of kernel
linear mapping and causes SLB recovery to fail.

Signed-off-by: Mahesh Salgaonkar <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Ignore this patch.. There are few spelling mistakes in this patch.. will
resend v2 again after fixing those.

Thanks,
-Mahesh.

On Thu, 2018-08-23 at 04:56:08 UTC, Mahesh J Salgaonkar wrote:

From: Mahesh Salgaonkar <redacted>

With the powrpc next commit e7e81847478 (poewrpc/mce: Fix SLB rebolting
during MCE recovery path.), the SLB error recovery is broken. The new
change now does not add index value to RB[52-63] that selects the SLB
entry while rebolting, instead it assumes that the shadow save area
already have index embeded correctly in esid field. While all valid bolted
save areas do contain index value set correctly, there is a case where
3rd (KSTACK_INDEX) entry for kernel stack does not embed index for NULL
esid entry. This patch fixes that.

Without this patch the SLB rebolt code overwirtes the 1st entry of kernel
linear mapping and causes SLB recovery to fail.

Signed-off-by: Mahesh Salgaonkar <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/0f52b3a00c789569d7ed822b5a6b30

cheers