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Re: [Qemu-ppc] [RFC PATCH] booke206: fix MAS update on tlb miss

From: KONRAD Frederic
Subject: Re: [Qemu-ppc] [RFC PATCH] booke206: fix MAS update on tlb miss
Date: Mon, 7 Aug 2017 14:49:06 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 08/03/2017 03:13 PM, Thomas Huth wrote:
On 03.08.2017 14:08, KONRAD Frederic wrote:

On 08/03/2017 01:37 PM, Thomas Huth wrote:
On 01.08.2017 10:44, KONRAD Frederic wrote:
When a tlb instruction miss happen, rw is set to 0 at the bottom
of cpu_ppc_handle_mmu_fault which cause the MAS update function to miss
the SAS and TS bit in MAS6, MAS1 in booke206_update_mas_tlb_miss.

Just calling booke206_update_mas_tlb_miss with rw = 2 solve the issue.

Signed-off-by: KONRAD Frederic <address@hidden>
   target/ppc/mmu_helper.c | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/ppc/mmu_helper.c b/target/ppc/mmu_helper.c
index b7b9088..f06b938 100644
--- a/target/ppc/mmu_helper.c
+++ b/target/ppc/mmu_helper.c
@@ -1551,7 +1551,7 @@ static int cpu_ppc_handle_mmu_fault(CPUPPCState
*env, target_ulong address,
                       env->spr[SPR_40x_ESR] = 0x00000000;
                   case POWERPC_MMU_BOOKE206:
-                    booke206_update_mas_tlb_miss(env, address, rw);
+                    booke206_update_mas_tlb_miss(env, address, 2);

Hi Thomas,

Couldn't that code path be called for normal data read miss (instead of
instruction miss), too?

I don't think so because we have access_type == ACCESS_CODE and
the code in cpu_ppc_handle_mmu_fault explicitely split the CODE
and DATA cases.

Ah, right, I missed that if-statement. So never mind about my comment!

Anyway, could we please use MMU_INST_FETCH instead of magic values like
2 here?

I agree it's not nice to have a magic value like this.. But it's
used all over the code there and david took the patch.

So I suggest I send a second patch to fix all the instances of
that magic value.

Sounds like a good idea!

Hi Thomas,

Looking more in details at this magic value, it seems rw is
not considered as an access type but more as an is_write boolean.

The whole mmu code use "int access_type" which is kind of
redundant / confusing if we change rw to be MMUAccessType.



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