Re: [PATCH v2 03/16] target/ppc: add exclusive user write function for MMCR0

[Daniel Henrique Barboza]

On 8/25/21 1:37 AM, David Gibson wrote:

On Tue, Aug 24, 2021 at 01:30:19PM -0300, Daniel Henrique Barboza wrote:

From: Gustavo Romero <grom...@linux.ibm.com>

Similar to the previous patch, user write on some PowerPC
PMU regs, in this case, MMCR0, is limited. Create a new
function to handle that.

Ok.. ok, this fixes my concern on the previous patch.  Best to avoid
the confusing interim step though.  I'm not sure there's a lot of use
adding the general "group A" helper if you're going to replace them
with more specific functions shortly afterwards.

Perhaps we should merge patches  2 and 3 together. I'll also take into
consideration that patch 15 will also add custom handling of more PMU
regs and, perhaps, drop patch 1 entirely since the only control left
for groupA will be MMCRA which can either be added separately or ignored
(the kernel EBB tests doesn't bother with MMCRA permissions).



Daniel

CC: Gustavo Romero <gustavo.rom...@linaro.org>
Signed-off-by: Gustavo Romero <grom...@linux.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
---
  target/ppc/cpu_init.c  |  2 +-
  target/ppc/spr_tcg.h   |  1 +
  target/ppc/translate.c | 38 ++++++++++++++++++++++++++++++++++++++
  3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
index 5510c3799f..860716da18 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_MMCR0_ureg, &spr_write_PMU_groupA_ureg,
+                 &spr_read_MMCR0_ureg, &spr_write_MMCR0_ureg,
                   &spr_read_ureg, &spr_write_ureg,
                   0x00000000);
      spr_register(env, SPR_POWER_UMMCR1, "UMMCR1",
diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
index 64ef2cd089..5c383dae3d 100644
--- a/target/ppc/spr_tcg.h
+++ b/target/ppc/spr_tcg.h
@@ -43,6 +43,7 @@ void spr_read_601_rtcu(DisasContext *ctx, int gprn, int sprn);
  void spr_read_spefscr(DisasContext *ctx, int gprn, int sprn);
  void spr_write_spefscr(DisasContext *ctx, int sprn, int gprn);
  void spr_write_PMU_groupA_ureg(DisasContext *ctx, int sprn, int gprn);
+void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn);

#ifndef CONFIG_USER_ONLY

  void spr_write_generic32(DisasContext *ctx, int sprn, int gprn);
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index ec4160378d..b48eec83e3 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -592,11 +592,49 @@ void spr_write_PMU_groupA_ureg(DisasContext *ctx, int 
sprn, int gprn)
      }
      spr_write_ureg(ctx, sprn, gprn);
  }
+
+void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
+{
+    TCGv t0, t1;
+
+    /*
+     * MMCR0 is a Group A SPR. The same write access control
+     * done in spr_write_PMU_groupA_ureg() applies.
+     */
+    if (ctx->pmcc_clear) {
+        gen_hvpriv_exception(ctx, POWERPC_EXCP_INVAL_SPR);
+        return;
+    }
+
+    t0 = tcg_temp_new();
+    t1 = 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.
+     */
+    tcg_gen_andi_tl(t0, cpu_gpr[gprn],
+                    MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE);
+    gen_load_spr(t1, SPR_POWER_MMCR0);
+    tcg_gen_andi_tl(t1, t1, ~(MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE));

Since you're reusing them again here, definitely want a #define for
this mask.

+    /* Keep all other bits intact */
+    tcg_gen_or_tl(t1, t1, t0);
+    gen_store_spr(SPR_POWER_MMCR0, t1);
+
+    tcg_temp_free(t0);
+    tcg_temp_free(t1);
+}
  #else
  void spr_write_PMU_groupA_ureg(DisasContext *ctx, int sprn, int gprn)
  {
      spr_noaccess(ctx, gprn, sprn);
  }
+
+void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
+{
+    spr_noaccess(ctx, gprn, sprn);
+}
  #endif

/* SPR common to all non-embedded PowerPC */