Re: [Qemu-devel] [PATCH 4/6] ppc/hash32: Rework R and C bit updates

[David Gibson]

On Thu, Apr 11, 2019 at 10:00:02AM +0200, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt <address@hidden>
> 
> With MT-TCG, we are now running translation in a racy way, thus
> we need to mimic hardware when it comes to updating the R and
> C bits, by doing byte stores.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> Signed-off-by: Cédric Le Goater <address@hidden>

Applied, thanks.

> ---
>  target/ppc/mmu-hash32.c | 45 ++++++++++++++++++++++++++++-------------
>  1 file changed, 31 insertions(+), 14 deletions(-)
> 
> diff --git a/target/ppc/mmu-hash32.c b/target/ppc/mmu-hash32.c
> index 3f4dee835e2d..55cf156a0b49 100644
> --- a/target/ppc/mmu-hash32.c
> +++ b/target/ppc/mmu-hash32.c
> @@ -345,6 +345,24 @@ static hwaddr ppc_hash32_pteg_search(PowerPCCPU *cpu, 
> hwaddr pteg_off,
>      return -1;
>  }
>  
> +static void ppc_hash32_set_r(PowerPCCPU *cpu, hwaddr pte_offset, uint32_t 
> pte1)
> +{
> +    target_ulong base = ppc_hash32_hpt_base(cpu);
> +    hwaddr offset = pte_offset + 6;
> +
> +    /* The HW performs a non-atomic byte update */
> +    stb_phys(CPU(cpu)->as, base + offset, ((pte1 >> 8) & 0xff) | 0x01);
> +}
> +
> +static void ppc_hash32_set_c(PowerPCCPU *cpu, hwaddr pte_offset, uint64_t 
> pte1)
> +{
> +    target_ulong base = ppc_hash32_hpt_base(cpu);
> +    hwaddr offset = pte_offset + 7;
> +
> +    /* The HW performs a non-atomic byte update */
> +    stb_phys(CPU(cpu)->as, base + offset, (pte1 & 0xff) | 0x80);
> +}
> +
>  static hwaddr ppc_hash32_htab_lookup(PowerPCCPU *cpu,
>                                       target_ulong sr, target_ulong eaddr,
>                                       ppc_hash_pte32_t *pte)
> @@ -403,7 +421,6 @@ int ppc_hash32_handle_mmu_fault(PowerPCCPU *cpu, vaddr 
> eaddr, int rwx,
>      hwaddr pte_offset;
>      ppc_hash_pte32_t pte;
>      int prot;
> -    uint32_t new_pte1;
>      const int need_prot[] = {PAGE_READ, PAGE_WRITE, PAGE_EXEC};
>      hwaddr raddr;
>  
> @@ -519,20 +536,20 @@ int ppc_hash32_handle_mmu_fault(PowerPCCPU *cpu, vaddr 
> eaddr, int rwx,
>  
>      /* 8. Update PTE referenced and changed bits if necessary */
>  
> -    new_pte1 = pte.pte1 | HPTE32_R_R; /* set referenced bit */
> -    if (rwx == 1) {
> -        new_pte1 |= HPTE32_R_C; /* set changed (dirty) bit */
> -    } else {
> -        /*
> -         * Treat the page as read-only for now, so that a later write
> -         * will pass through this function again to set the C bit
> -         */
> -        prot &= ~PAGE_WRITE;
> -    }
> -
> -    if (new_pte1 != pte.pte1) {
> -        ppc_hash32_store_hpte1(cpu, pte_offset, new_pte1);
> +    if (!(pte.pte1 & HPTE32_R_R)) {
> +        ppc_hash32_set_r(cpu, pte_offset, pte.pte1);
>      }
> +    if (!(pte.pte1 & HPTE32_R_C)) {
> +        if (rwx == 1) {
> +            ppc_hash32_set_c(cpu, pte_offset, pte.pte1);
> +        } else {
> +            /*
> +             * Treat the page as read-only for now, so that a later write
> +             * will pass through this function again to set the C bit
> +             */
> +            prot &= ~PAGE_WRITE;
> +        }
> +     }
>  
>      /* 9. Determine the real address from the PTE */
>  

-- 
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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