Re: [PATCH v2] target/ppc: fix Hash64 MMU update of PTE bit R

[David Gibson]

On Thu, Nov 25, 2021 at 03:33:22PM -0300, Leandro Lupori wrote:
> When updating the R bit of a PTE, the Hash64 MMU was using a wrong byte
> offset, causing the first byte of the adjacent PTE to be corrupted.
> This caused a panic when booting FreeBSD, using the Hash MMU.
> 
> Fixes: a2dd4e83e76b ("ppc/hash64: Rework R and C bit updates")
> Signed-off-by: Leandro Lupori <leandro.lupori@eldorado.org.br>

If you're introducing the constant, it would make sense to also use it
in spapr_hpte_set_r().

> ---
> Changes from v1:
> - Add and use a new define for the byte offset of PTE bit R
> ---
>  target/ppc/mmu-hash64.c | 2 +-
>  target/ppc/mmu-hash64.h | 3 +++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> index 19832c4b46..0968927744 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -786,7 +786,7 @@ static void ppc_hash64_set_dsi(CPUState *cs, int mmu_idx, 
> uint64_t dar, uint64_t
>  
>  static void ppc_hash64_set_r(PowerPCCPU *cpu, hwaddr ptex, uint64_t pte1)
>  {
> -    hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + 16;
> +    hwaddr base, offset = ptex * HASH_PTE_SIZE_64 + HPTE64_R_R_BYTE_OFFSET;
>  
>      if (cpu->vhyp) {
>          PPCVirtualHypervisorClass *vhc =
> diff --git a/target/ppc/mmu-hash64.h b/target/ppc/mmu-hash64.h
> index c5b2f97ff7..40bb901262 100644
> --- a/target/ppc/mmu-hash64.h
> +++ b/target/ppc/mmu-hash64.h
> @@ -97,6 +97,9 @@ void ppc_hash64_finalize(PowerPCCPU *cpu);
>  #define HPTE64_V_1TB_SEG        0x4000000000000000ULL
>  #define HPTE64_V_VRMA_MASK      0x4001ffffff000000ULL
>  
> +/* PTE byte offsets */
> +#define HPTE64_R_R_BYTE_OFFSET  14
> +
>  /* Format changes for ARCH v3 */
>  #define HPTE64_V_COMMON_BITS    0x000fffffffffffffULL
>  #define HPTE64_R_3_0_SSIZE_SHIFT 58

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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