Re: [PATCH v2 02/16] target/ppc: add user read functions for MMCR0 and MMCR2

[David Gibson]

On Tue, Aug 24, 2021 at 01:30:18PM -0300, Daniel Henrique Barboza wrote:
> From: Gustavo Romero <gromero@linux.ibm.com>
> 
> This patch adds handling of UMMCR0 and UMMCR2 user read which,
> according to PowerISA 3.1, has some bits ommited to the

Nit: One 'm' in "omited".

> userspace.
> 
> CC: Gustavo Romero <gustavo.romero@linaro.org>
> Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  target/ppc/cpu.h       |  5 +++++
>  target/ppc/cpu_init.c  |  4 ++--
>  target/ppc/spr_tcg.h   |  2 ++
>  target/ppc/translate.c | 37 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 46 insertions(+), 2 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 627fc8d732..739005ba29 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -343,6 +343,11 @@ typedef struct ppc_v3_pate_t {
>  #define MSR_LE   0  /* Little-endian mode                           1 hflags 
> */
>  
>  /* PMU bits */
> +#define MMCR0_FC    PPC_BIT(32)         /* Freeze Counters  */
> +#define MMCR0_PMAO  PPC_BIT(56)         /* Perf Monitor Alert Ocurred */
> +#define MMCR0_PMAE  PPC_BIT(37)         /* Perf Monitor Alert Enable */
> +#define MMCR0_EBE   PPC_BIT(43)         /* Perf Monitor EBB Enable */
> +#define MMCR0_FCECE PPC_BIT(38)         /* FC on Enabled Cond or Event */
>  #define MMCR0_PMCC  PPC_BITMASK(44, 45) /* PMC Control */
>  
>  /* LPCR bits */
> diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> index c72c7fabea..5510c3799f 100644
> --- a/target/ppc/cpu_init.c
> +++ b/target/ppc/cpu_init.c
> @@ -6868,7 +6868,7 @@ static void register_book3s_pmu_sup_sprs(CPUPPCState 
> *env)
>  static void register_book3s_pmu_user_sprs(CPUPPCState *env)
>  {
>      spr_register(env, SPR_POWER_UMMCR0, "UMMCR0",
> -                 &spr_read_ureg, &spr_write_PMU_groupA_ureg,
> +                 &spr_read_MMCR0_ureg, &spr_write_PMU_groupA_ureg,

Hrm.. so combined with the previous patch this means that userspace
can write any bit in MMCR0, but only read some of them.  Is that
really correct?

>                   &spr_read_ureg, &spr_write_ureg,
>                   0x00000000);
>      spr_register(env, SPR_POWER_UMMCR1, "UMMCR1",
> @@ -6976,7 +6976,7 @@ static void register_power8_pmu_sup_sprs(CPUPPCState 
> *env)
>  static void register_power8_pmu_user_sprs(CPUPPCState *env)
>  {
>      spr_register(env, SPR_POWER_UMMCR2, "UMMCR2",
> -                 &spr_read_ureg, &spr_write_PMU_groupA_ureg,
> +                 &spr_read_MMCR2_ureg, &spr_write_PMU_groupA_ureg,
>                   &spr_read_ureg, &spr_write_ureg,
>                   0x00000000);
>      spr_register(env, SPR_POWER_USIER, "USIER",
> diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
> index 027ec4c3f7..64ef2cd089 100644
> --- a/target/ppc/spr_tcg.h
> +++ b/target/ppc/spr_tcg.h
> @@ -32,6 +32,8 @@ void spr_write_lr(DisasContext *ctx, int sprn, int gprn);
>  void spr_read_ctr(DisasContext *ctx, int gprn, int sprn);
>  void spr_write_ctr(DisasContext *ctx, int sprn, int gprn);
>  void spr_read_ureg(DisasContext *ctx, int gprn, int sprn);
> +void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn);
> +void spr_read_MMCR2_ureg(DisasContext *ctx, int gprn, int sprn);
>  void spr_read_tbl(DisasContext *ctx, int gprn, int sprn);
>  void spr_read_tbu(DisasContext *ctx, int gprn, int sprn);
>  void spr_read_atbl(DisasContext *ctx, int gprn, int sprn);
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 3a1eafbba8..ec4160378d 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -520,6 +520,43 @@ void spr_read_ureg(DisasContext *ctx, int gprn, int sprn)
>      gen_load_spr(cpu_gpr[gprn], sprn + 0x10);
>  }
>  
> +void spr_read_MMCR0_ureg(DisasContext *ctx, int gprn, int sprn)
> +{
> +    TCGv t0 = tcg_temp_new();
> +
> +    /*
> +     * Filter out all bits but FC, PMAO, and PMAE, according
> +     * to ISA v3.1, in 10.4.4 Monitor Mode Control Register 0,
> +     * fourth paragraph.
> +     */
> +    gen_load_spr(t0, SPR_POWER_MMCR0);
> +    tcg_gen_andi_tl(t0, t0, MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE);

I think #defining this mask somewhere would be worthwhile.

> +    tcg_gen_mov_tl(cpu_gpr[gprn], t0);
> +
> +    tcg_temp_free(t0);
> +}
> +
> +void spr_read_MMCR2_ureg(DisasContext *ctx, int gprn, int sprn)
> +{
> +    TCGv t0 = tcg_temp_new();
> +
> +    /*
> +     * On read, filter out all bits that are not FCnP0 bits.
> +     * When MMCR0[PMCC] is set to 0b10 or 0b11, providing
> +     * problem state programs read/write access to MMCR2,
> +     * only the FCnP0 bits can be accessed. All other bits are
> +     * not changed when mtspr is executed in problem state, and
> +     * all other bits return 0s when mfspr is executed in problem
> +     * state, according to ISA v3.1, section 10.4.6 Monitor Mode
> +     * Control Register 2, p. 1316, third paragraph.
> +     */
> +    gen_load_spr(t0, SPR_POWER_MMCR2);
> +    tcg_gen_andi_tl(t0, t0, 0x4020100804020000UL);

Even more so here, where it's a big bare literal.

> +    tcg_gen_mov_tl(cpu_gpr[gprn], t0);
> +
> +    tcg_temp_free(t0);
> +}
> +
>  #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
>  void spr_write_ureg(DisasContext *ctx, int sprn, int gprn)
>  {

-- 
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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