Re: [Qemu-ppc] [PATCH V2 07/10] target/ppc: Flush TLB on write to PIDR

[David Gibson]

On Wed, Mar 01, 2017 at 06:12:58PM +1100, Suraj Jitindar Singh wrote:
> The PIDR (process id register) is used to store the id of the currently
> running process, which is used to select the process table entry used to
> perform address translation. This means that when we write to this register
> all the translations in the TLB become outdated as they are for a
> previously running process. Thus when this register is written to we need
> to invalidate the TLB entries to ensure stale entries aren't used to
> to perform translation for the new process, which would result in at best
> segfaults or alternatively just random memory being accessed.
> 
> Signed-off-by: Suraj Jitindar Singh <address@hidden>

Reviewed-by: David Gibson <address@hidden>

> ---
>  target/ppc/helper.h         | 1 +
>  target/ppc/misc_helper.c    | 8 ++++++++
>  target/ppc/translate_init.c | 8 +++++++-
>  3 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/helper.h b/target/ppc/helper.h
> index 6d77661..bb6a94a 100644
> --- a/target/ppc/helper.h
> +++ b/target/ppc/helper.h
> @@ -709,6 +709,7 @@ DEF_HELPER_FLAGS_1(load_601_rtcu, TCG_CALL_NO_RWG, tl, 
> env)
>  DEF_HELPER_FLAGS_1(load_purr, TCG_CALL_NO_RWG, tl, env)
>  #endif
>  DEF_HELPER_2(store_sdr1, void, env, tl)
> +DEF_HELPER_2(store_pidr, void, env, tl)
>  DEF_HELPER_FLAGS_2(store_tbl, TCG_CALL_NO_RWG, void, env, tl)
>  DEF_HELPER_FLAGS_2(store_tbu, TCG_CALL_NO_RWG, void, env, tl)
>  DEF_HELPER_FLAGS_2(store_atbl, TCG_CALL_NO_RWG, void, env, tl)
> diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
> index fa573dd..0e42178 100644
> --- a/target/ppc/misc_helper.c
> +++ b/target/ppc/misc_helper.c
> @@ -88,6 +88,14 @@ void helper_store_sdr1(CPUPPCState *env, target_ulong val)
>      }
>  }
>  
> +void helper_store_pidr(CPUPPCState *env, target_ulong val)
> +{
> +    PowerPCCPU *cpu = ppc_env_get_cpu(env);
> +
> +    env->spr[SPR_BOOKS_PID] = val;
> +    tlb_flush(CPU(cpu));
> +}
> +
>  void helper_store_hid0_601(CPUPPCState *env, target_ulong val)
>  {
>      target_ulong hid0;
> diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> index b2dc452..d8bb6ac 100644
> --- a/target/ppc/translate_init.c
> +++ b/target/ppc/translate_init.c
> @@ -395,6 +395,12 @@ static void spr_write_sdr1 (DisasContext *ctx, int sprn, 
> int gprn)
>      gen_helper_store_sdr1(cpu_env, cpu_gpr[gprn]);
>  }
>  
> +/* PIDR */
> +static void spr_write_pidr(DisasContext *ctx, int sprn, int gprn)
> +{
> +    gen_helper_store_pidr(cpu_env, cpu_gpr[gprn]);
> +}
> +
>  /* 64 bits PowerPC specific SPRs */
>  #if defined(TARGET_PPC64)
>  static void spr_read_hior (DisasContext *ctx, int gprn, int sprn)
> @@ -8201,7 +8207,7 @@ static void gen_spr_power8_book4(CPUPPCState *env)
>                       KVM_REG_PPC_ACOP, 0);
>      spr_register_kvm(env, SPR_BOOKS_PID, "PID",
>                       SPR_NOACCESS, SPR_NOACCESS,
> -                     &spr_read_generic, &spr_write_generic,
> +                     &spr_read_generic, &spr_write_pidr,
>                       KVM_REG_PPC_PID, 0);
>      spr_register_kvm(env, SPR_WORT, "WORT",
>                       SPR_NOACCESS, SPR_NOACCESS,

-- 
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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