Re: [PATCH v2 1/1] ppc/mmu_helper.c: do not truncate 'ea' in booke206_invalidate_ea_tlb()

[Cédric Le Goater]

On 11/10/21 21:25, Daniel Henrique Barboza wrote:
> 'tlbivax' is implemented by gen_tlbivax_booke206() via
> gen_helper_booke206_tlbivax(). In case the TLB needs to be flushed,
> booke206_invalidate_ea_tlb() is called. All these functions, but
> booke206_invalidate_ea_tlb(), uses a 64-bit effective address 'ea'.
>
> booke206_invalidate_ea_tlb() uses an uint32_t 'ea' argument that
> truncates the original 'ea' value for apparently no particular reason.
> This function retrieves the tlb pointer by calling booke206_get_tlbm(),
> which also uses a target_ulong address as parameter - in this case, a
> truncated 'ea' address. All the surrounding logic considers the
> effective TLB address as a 64 bit value, aside from the signature of
> booke206_invalidate_ea_tlb().
>
> Last but not the least, PowerISA 2.07B section 6.11.4.9 [2] makes it
> clear that the effective address "EA" is a 64 bit value.
>
> Commit 01662f3e5133 introduced this code and no changes were made ever
> since. An user detected a problem with tlbivax [1] stating that this
> address truncation was the cause. This same behavior might be the source
> of several subtle bugs that were never caught.
>
> For all these reasons, this patch assumes that this address truncation
> is the result of a mistake/oversight of the original commit, and changes
> booke206_invalidate_ea_tlb() 'ea' argument to 'vaddr'.
>
> [1] https://gitlab.com/qemu-project/qemu/-/issues/52
> [2] https://wiki.raptorcs.com/wiki/File:PowerISA_V2.07B.pdf
>
> Fixes: 01662f3e5133 ("PPC: Implement e500 (FSL) MMU")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/52
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>   target/ppc/mmu_helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

It looks correct. I am not sure why we introduced PPC_TLBIVAX since
we don't use it for the instruction. But e200 needs it AFAICT.

Any how,

Queued for 6.2

Thanks,

C.


> diff --git a/target/ppc/mmu_helper.c b/target/ppc/mmu_helper.c
> index 2cb98c5169..e0c4950dda 100644
> --- a/target/ppc/mmu_helper.c
> +++ b/target/ppc/mmu_helper.c
> @@ -1216,7 +1216,7 @@ void helper_booke206_tlbsx(CPUPPCState *env, target_ulong 
> address)
>   }
>   
>   static inline void booke206_invalidate_ea_tlb(CPUPPCState *env, int tlbn,
> -                                              uint32_t ea)
> +                                              vaddr ea)
>   {
>       int i;
>       int ways = booke206_tlb_ways(env, tlbn);