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* [PATCH v2] RISC-V: Add support for Ztso
  2023-11-13  9:56 [RFC PATCH 0/2] RISC-V: Add TSO extensions (Ztso/Ssdtso) Christoph Muellner
@ 2023-11-13  9:56 ` Christoph Muellner
  2023-11-13  9:56 ` [RFC PATCH 2/2] RISC-V: Add support for Ssdtso Christoph Muellner
  1 sibling, 0 replies; 10+ messages in thread
From: Palmer Dabbelt @ 2022-09-17  7:26 UTC (permalink / raw)
  To: qemu-devel, Richard Henderson; +Cc: Palmer Dabbelt

The Ztso extension was recently frozen, this adds it as a CPU property
and adds various fences throughout the port in order to allow TSO
targets to function on weaker hosts.  We need no fences for AMOs as
they're already SC, the placess we need barriers are described.

Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---
Like the v1 this has been pretty minimally tested, but I figured I'd
just send it.  This is what I would have done the first time had I not
read that comment near TCG_GUEST_DEFAULT_MO, I think trying to describe
that when I ran into Richard at the Cauldron was probably more confusing
than just digging up the code and sending it along.
---
 target/riscv/cpu.c                      |  3 +++
 target/riscv/cpu.h                      |  1 +
 target/riscv/insn_trans/trans_rva.c.inc | 11 ++++++++---
 target/riscv/insn_trans/trans_rvi.c.inc | 16 ++++++++++++++--
 target/riscv/insn_trans/trans_rvv.c.inc | 20 ++++++++++++++++++++
 target/riscv/translate.c                |  3 +++
 6 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index ac6f82ebd0..d66169efa5 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -919,6 +919,8 @@ static Property riscv_cpu_extensions[] = {
     DEFINE_PROP_BOOL("zhinx", RISCVCPU, cfg.ext_zhinx, false),
     DEFINE_PROP_BOOL("zhinxmin", RISCVCPU, cfg.ext_zhinxmin, false),
 
+    DEFINE_PROP_BOOL("ztso", RISCVCPU, cfg.ext_ztso, false),
+
     /* Vendor-specific custom extensions */
     DEFINE_PROP_BOOL("xventanacondops", RISCVCPU, cfg.ext_XVentanaCondOps, false),
 
@@ -1094,6 +1096,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char **isa_str, int max_str_len)
         ISA_EDATA_ENTRY(zksed, ext_zksed),
         ISA_EDATA_ENTRY(zksh, ext_zksh),
         ISA_EDATA_ENTRY(zkt, ext_zkt),
+        ISA_EDATA_ENTRY(ztso, ext_ztso),
         ISA_EDATA_ENTRY(zve32f, ext_zve32f),
         ISA_EDATA_ENTRY(zve64f, ext_zve64f),
         ISA_EDATA_ENTRY(zhinx, ext_zhinx),
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 5c7acc055a..c64fd4e258 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -433,6 +433,7 @@ struct RISCVCPUConfig {
     bool ext_zve32f;
     bool ext_zve64f;
     bool ext_zmmul;
+    bool ext_ztso;
     bool rvv_ta_all_1s;
 
     uint32_t mvendorid;
diff --git a/target/riscv/insn_trans/trans_rva.c.inc b/target/riscv/insn_trans/trans_rva.c.inc
index 45db82c9be..9066e1bde3 100644
--- a/target/riscv/insn_trans/trans_rva.c.inc
+++ b/target/riscv/insn_trans/trans_rva.c.inc
@@ -26,7 +26,11 @@ static bool gen_lr(DisasContext *ctx, arg_atomic *a, MemOp mop)
         tcg_gen_mb(TCG_MO_ALL | TCG_BAR_STRL);
     }
     tcg_gen_qemu_ld_tl(load_val, src1, ctx->mem_idx, mop);
-    if (a->aq) {
+    /*
+     * TSO defines AMOs as acquire+release-RCsc, but does not define LR/SC as
+     * AMOs.  Instead treat them like loads.
+     */
+    if (a->aq || ctx->ztso) {
         tcg_gen_mb(TCG_MO_ALL | TCG_BAR_LDAQ);
     }
 
@@ -61,9 +65,10 @@ static bool gen_sc(DisasContext *ctx, arg_atomic *a, MemOp mop)
     gen_set_label(l1);
     /*
      * Address comparison failure.  However, we still need to
-     * provide the memory barrier implied by AQ/RL.
+     * provide the memory barrier implied by AQ/RL/TSO.
      */
-    tcg_gen_mb(TCG_MO_ALL + a->aq * TCG_BAR_LDAQ + a->rl * TCG_BAR_STRL);
+    TCGBar bar_strl = (ctx->ztso || a->rl) ? TCG_BAR_STRL : 0;
+    tcg_gen_mb(TCG_MO_ALL + a->aq * TCG_BAR_LDAQ + bar_strl);
     gen_set_gpr(ctx, a->rd, tcg_constant_tl(1));
 
     gen_set_label(l2);
diff --git a/target/riscv/insn_trans/trans_rvi.c.inc b/target/riscv/insn_trans/trans_rvi.c.inc
index ca8e3d1ea1..9bef42a3e5 100644
--- a/target/riscv/insn_trans/trans_rvi.c.inc
+++ b/target/riscv/insn_trans/trans_rvi.c.inc
@@ -261,11 +261,19 @@ static bool gen_load_i128(DisasContext *ctx, arg_lb *a, MemOp memop)
 
 static bool gen_load(DisasContext *ctx, arg_lb *a, MemOp memop)
 {
+    bool out;
+
     if (get_xl(ctx) == MXL_RV128) {
-        return gen_load_i128(ctx, a, memop);
+        out = gen_load_i128(ctx, a, memop);
     } else {
-        return gen_load_tl(ctx, a, memop);
+        out = gen_load_tl(ctx, a, memop);
+    }
+
+    if (ctx->ztso) {
+        tcg_gen_mb(TCG_MO_ALL | TCG_BAR_LDAQ);
     }
+
+    return out;
 }
 
 static bool trans_lb(DisasContext *ctx, arg_lb *a)
@@ -322,6 +330,10 @@ static bool gen_store_tl(DisasContext *ctx, arg_sb *a, MemOp memop)
     TCGv addr = get_address(ctx, a->rs1, a->imm);
     TCGv data = get_gpr(ctx, a->rs2, EXT_NONE);
 
+    if (ctx->ztso) {
+        tcg_gen_mb(TCG_MO_ALL | TCG_BAR_STRL);
+    }
+
     tcg_gen_qemu_st_tl(data, addr, ctx->mem_idx, memop);
     return true;
 }
diff --git a/target/riscv/insn_trans/trans_rvv.c.inc b/target/riscv/insn_trans/trans_rvv.c.inc
index 6c091824b6..1994b38035 100644
--- a/target/riscv/insn_trans/trans_rvv.c.inc
+++ b/target/riscv/insn_trans/trans_rvv.c.inc
@@ -671,8 +671,28 @@ static bool ldst_us_trans(uint32_t vd, uint32_t rs1, uint32_t data,
     tcg_gen_addi_ptr(dest, cpu_env, vreg_ofs(s, vd));
     tcg_gen_addi_ptr(mask, cpu_env, vreg_ofs(s, 0));
 
+    /*
+     * According to the specification
+     *
+     *   Additionally, if the Ztso extension is implemented, then vector memory
+     *   instructions in the V extension and Zve family of extensions follow
+     *   RVTSO at the instruction level.  The Ztso extension does not
+     *   strengthen the ordering of intra-instruction element accesses.
+     *
+     * as a result neither ordered nor unordered accesses from the V
+     * instructions need ordering within the loop but we do still need barriers
+     * around the loop.
+     */
+    if (is_store && s->ztso) {
+      tcg_gen_mb(TCG_MO_ALL | TCG_BAR_STRL);
+    }
+
     fn(dest, mask, base, cpu_env, desc);
 
+    if (!is_store && s->ztso) {
+      tcg_gen_mb(TCG_MO_ALL | TCG_BAR_LDAQ);
+    }
+
     tcg_temp_free_ptr(dest);
     tcg_temp_free_ptr(mask);
 
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 63b04e8a94..c7c574b09f 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -109,6 +109,8 @@ typedef struct DisasContext {
     /* PointerMasking extension */
     bool pm_mask_enabled;
     bool pm_base_enabled;
+    /* Ztso */
+    bool ztso;
     /* TCG of the current insn_start */
     TCGOp *insn_start;
 } DisasContext;
@@ -1109,6 +1111,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     memset(ctx->ftemp, 0, sizeof(ctx->ftemp));
     ctx->pm_mask_enabled = FIELD_EX32(tb_flags, TB_FLAGS, PM_MASK_ENABLED);
     ctx->pm_base_enabled = FIELD_EX32(tb_flags, TB_FLAGS, PM_BASE_ENABLED);
+    ctx->ztso = cpu->cfg.ext_ztso;
     ctx->zero = tcg_constant_tl(0);
 }
 
-- 
2.34.1



^ permalink raw reply related	[flat|nested] 10+ messages in thread
* [RFC PATCH 0/2] RISC-V: Add TSO extensions (Ztso/Ssdtso)
@ 2023-11-13  9:56 Christoph Muellner
  2023-11-13  9:56 ` [RFC PATCH 1/2] RISC-V: Add support for Ztso Christoph Muellner
  2023-11-13  9:56 ` [RFC PATCH 2/2] RISC-V: Add support for Ssdtso Christoph Muellner
  0 siblings, 2 replies; 10+ messages in thread
From: Christoph Muellner @ 2023-11-13  9:56 UTC (permalink / raw)
  To: qemu-riscv, qemu-devel, Alistair Francis, Bin Meng,
	Philipp Tomsich, Palmer Dabbelt, Richard Henderson
  Cc: Christoph Müllner

From: Christoph Müllner <christoph.muellner@vrull.eu>

This series picks up an earlier v2 Ztso patch from Palmer
and adds a second to support Ssdtso.

Palmer's v2 Ztso patch can be found here:
  https://patchwork.kernel.org/project/qemu-devel/patch/20220917072635.11616-1-palmer@rivosinc.com/
This patch did not apply cleanly but the necessary changes were trivial.
There was a request to extend the commit message, which is part of the
posted patch of this series.  As this patch was reviewed a year ago,
I believe it could be merged.

The second patch adds support for dynamic TSO following the second
draft of the Ssdtso extension, which was published recently:
  https://lists.riscv.org/g/tech-arch-review/message/183
Note, that the Ssdtso specification is in development state
(i.e., not frozen or even ratified) which is also the reason
why I marked the series as RFC.

Relevant in this context might be also, that Richard's patch to improve
TCG's memory barrier selection depending on host and guest memory ordering
landed in June:
  https://lore.kernel.org/all/a313b36b-dcc1-f812-ccbd-afed1cbd523b@linaro.org/T/

Christoph Müllner (1):
  RISC-V: Add support for Ssdtso

Palmer Dabbelt (1):
  RISC-V: Add support for Ztso

 target/riscv/cpu.c                      |  4 ++++
 target/riscv/cpu_bits.h                 |  3 +++
 target/riscv/cpu_cfg.h                  |  2 ++
 target/riscv/csr.c                      |  9 ++++++---
 target/riscv/insn_trans/trans_rva.c.inc | 11 ++++++++---
 target/riscv/insn_trans/trans_rvi.c.inc | 16 ++++++++++++++--
 target/riscv/insn_trans/trans_rvv.c.inc | 20 ++++++++++++++++++++
 target/riscv/translate.c                |  3 +++
 8 files changed, 60 insertions(+), 8 deletions(-)

-- 
2.41.0



^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2023-11-14 13:23 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-17  7:26 [PATCH v2] RISC-V: Add support for Ztso Palmer Dabbelt
2023-11-13  9:56 ` Christoph Muellner
2022-09-23  4:35 ` Alistair Francis
2022-09-23 10:49   ` Palmer Dabbelt
2022-09-25 10:28     ` Richard Henderson
2023-11-13  9:56 [RFC PATCH 0/2] RISC-V: Add TSO extensions (Ztso/Ssdtso) Christoph Muellner
2023-11-13  9:56 ` [RFC PATCH 1/2] RISC-V: Add support for Ztso Christoph Muellner
2023-11-14 13:22   ` Daniel Henrique Barboza
2023-11-13  9:56 ` [RFC PATCH 2/2] RISC-V: Add support for Ssdtso Christoph Muellner
2023-11-14 13:23   ` Daniel Henrique Barboza

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