Re: [Qemu-devel] [PATCH v2 03/17] RISC-V: support vector extension csr

[Palmer Dabbelt]

On Wed, 11 Sep 2019 15:43:29 PDT (-0700), richard.hender...@linaro.org wrote:

On 9/11/19 2:25 AM, liuzhiwei wrote:

@@ -873,7 +925,12 @@ static riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
 [CSR_FFLAGS] =  { fs,   read_fflags,  write_fflags  },
 [CSR_FRM] = { fs,   read_frm, write_frm },
 [CSR_FCSR] ={ fs,   read_fcsr,write_fcsr},
-
+/* Vector CSRs */
+[CSR_VSTART] =  { any,   read_vstart, write_vstart  },
+[CSR_VXSAT] =   { any,   read_vxsat,  write_vxsat   },
+[CSR_VXRM] ={ any,   read_vxrm,   write_vxrm},
+[CSR_VL] =  { any,   read_vl},
+[CSR_VTYPE] =   { any,   read_vtype },


Is there really no MSTATUS bit to disable the vector unit,
as there is for the FPU?  That seems like a defect in the
specification if true...


The privileged part of the V extension hasn't been written yet, which is part 
of the reason this is a draft that we know will change.  We're letting it into 
QEMU so people can more easily prototype software, but won't be letting it into 
Linux or GCC to avoid users depending on behavior that will change in the 
future.

Re: [Qemu-devel] [PATCH v2 03/17] RISC-V: support vector extension csr

[Richard Henderson]

On 9/11/19 2:25 AM, liuzhiwei wrote:
> @@ -873,7 +925,12 @@ static riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>  [CSR_FFLAGS] =  { fs,   read_fflags,  write_fflags  
> },
>  [CSR_FRM] = { fs,   read_frm, write_frm 
> },
>  [CSR_FCSR] ={ fs,   read_fcsr,write_fcsr
> },
> -
> +/* Vector CSRs */
> +[CSR_VSTART] =  { any,   read_vstart, write_vstart  
> },
> +[CSR_VXSAT] =   { any,   read_vxsat,  write_vxsat   
> },
> +[CSR_VXRM] ={ any,   read_vxrm,   write_vxrm
> },
> +[CSR_VL] =  { any,   read_vl
> },
> +[CSR_VTYPE] =   { any,   read_vtype 
> },

Is there really no MSTATUS bit to disable the vector unit,
as there is for the FPU?  That seems like a defect in the
specification if true...


r~

[Qemu-devel] [PATCH v2 03/17] RISC-V: support vector extension csr

[liuzhiwei]

From: LIU Zhiwei 

Signed-off-by: LIU Zhiwei 
---
 target/riscv/cpu_bits.h | 15 
 target/riscv/csr.c  | 65 ++---
 2 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index 11f971a..9eb43ec 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -29,6 +29,14 @@
 #define FSR_NXA (FPEXC_NX << FSR_AEXC_SHIFT)
 #define FSR_AEXC(FSR_NVA | FSR_OFA | FSR_UFA | FSR_DZA | FSR_NXA)
 
+/* Vector Fixed-Point round model */
+#define FSR_VXRM_SHIFT  9
+#define FSR_VXRM(0x3 << FSR_VXRM_SHIFT)
+
+/* Vector Fixed-Point saturation flag */
+#define FSR_VXSAT_SHIFT 8
+#define FSR_VXSAT   (0x1 << FSR_VXSAT_SHIFT)
+
 /* Control and Status Registers */
 
 /* User Trap Setup */
@@ -48,6 +56,13 @@
 #define CSR_FRM 0x002
 #define CSR_FCSR0x003
 
+/* User Vector CSRs */
+#define CSR_VSTART  0x008
+#define CSR_VXSAT   0x009
+#define CSR_VXRM0x00a
+#define CSR_VL  0xc20
+#define CSR_VTYPE   0xc21
+
 /* User Timers and Counters */
 #define CSR_CYCLE   0xc00
 #define CSR_TIME0xc01
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index e0d4586..a6131ff 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -87,12 +87,12 @@ static int ctr(CPURISCVState *env, int csrno)
 return 0;
 }
 
-#if !defined(CONFIG_USER_ONLY)
 static int any(CPURISCVState *env, int csrno)
 {
 return 0;
 }
 
+#if !defined(CONFIG_USER_ONLY)
 static int smode(CPURISCVState *env, int csrno)
 {
 return -!riscv_has_ext(env, RVS);
@@ -158,8 +158,10 @@ static int read_fcsr(CPURISCVState *env, int csrno, 
target_ulong *val)
 return -1;
 }
 #endif
-*val = (riscv_cpu_get_fflags(env) << FSR_AEXC_SHIFT)
-| (env->frm << FSR_RD_SHIFT);
+*val = (env->vfp.vxrm << FSR_VXRM_SHIFT)
+| (env->vfp.vxsat << FSR_VXSAT_SHIFT)
+| (riscv_cpu_get_fflags(env) << FSR_AEXC_SHIFT)
+| (env->frm << FSR_RD_SHIFT);
 return 0;
 }
 
@@ -172,10 +174,60 @@ static int write_fcsr(CPURISCVState *env, int csrno, 
target_ulong val)
 env->mstatus |= MSTATUS_FS;
 #endif
 env->frm = (val & FSR_RD) >> FSR_RD_SHIFT;
+env->vfp.vxrm = (val & FSR_VXRM) >> FSR_VXRM_SHIFT;
+env->vfp.vxsat = (val & FSR_VXSAT) >> FSR_VXSAT_SHIFT;
 riscv_cpu_set_fflags(env, (val & FSR_AEXC) >> FSR_AEXC_SHIFT);
 return 0;
 }
 
+static int read_vtype(CPURISCVState *env, int csrno, target_ulong *val)
+{
+*val = env->vfp.vtype;
+return 0;
+}
+
+static int read_vl(CPURISCVState *env, int csrno, target_ulong *val)
+{
+*val = env->vfp.vl;
+return 0;
+}
+
+static int read_vxrm(CPURISCVState *env, int csrno, target_ulong *val)
+{
+*val = env->vfp.vxrm;
+return 0;
+}
+
+static int read_vxsat(CPURISCVState *env, int csrno, target_ulong *val)
+{
+*val = env->vfp.vxsat;
+return 0;
+}
+
+static int read_vstart(CPURISCVState *env, int csrno, target_ulong *val)
+{
+*val = env->vfp.vstart;
+return 0;
+}
+
+static int write_vxrm(CPURISCVState *env, int csrno, target_ulong val)
+{
+env->vfp.vxrm = val;
+return 0;
+}
+
+static int write_vxsat(CPURISCVState *env, int csrno, target_ulong val)
+{
+env->vfp.vxsat = val;
+return 0;
+}
+
+static int write_vstart(CPURISCVState *env, int csrno, target_ulong val)
+{
+env->vfp.vstart = val;
+return 0;
+}
+
 /* User Timers and Counters */
 static int read_instret(CPURISCVState *env, int csrno, target_ulong *val)
 {
@@ -873,7 +925,12 @@ static riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
 [CSR_FFLAGS] =  { fs,   read_fflags,  write_fflags  },
 [CSR_FRM] = { fs,   read_frm, write_frm },
 [CSR_FCSR] ={ fs,   read_fcsr,write_fcsr},
-
+/* Vector CSRs */
+[CSR_VSTART] =  { any,   read_vstart, write_vstart  },
+[CSR_VXSAT] =   { any,   read_vxsat,  write_vxsat   },
+[CSR_VXRM] ={ any,   read_vxrm,   write_vxrm},
+[CSR_VL] =  { any,   read_vl},
+[CSR_VTYPE] =   { any,   read_vtype },
 /* User Timers and Counters */
 [CSR_CYCLE] =   { ctr,  read_instret},
 [CSR_INSTRET] = { ctr,  read_instret},
-- 
2.7.4