target/riscv: Implement AIA xiselect and xireg CSRs

The AIA specification defines [m|s|vs]iselect and [m|s|vs]ireg CSRs
which allow indirect access to interrupt priority arrays and per-HART
IMSIC registers. This patch implements AIA xiselect and xireg CSRs.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Message-id: 20220204174700.534953-15-anup@brainfault.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 177 insertions, 0 deletions

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 39402a6a49..a186b31fcf 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -931,6 +931,169 @@ static int read_mtopi(CPURISCVState *env, int csrno, target_ulong *val)
     return RISCV_EXCP_NONE;
 }
 
+static int aia_xlate_vs_csrno(CPURISCVState *env, int csrno)
+{
+    if (!riscv_cpu_virt_enabled(env)) {
+        return csrno;
+    }
+
+    switch (csrno) {
+    case CSR_SISELECT:
+        return CSR_VSISELECT;
+    case CSR_SIREG:
+        return CSR_VSIREG;
+    default:
+        return csrno;
+    };
+}
+
+static int rmw_xiselect(CPURISCVState *env, int csrno, target_ulong *val,
+                        target_ulong new_val, target_ulong wr_mask)
+{
+    target_ulong *iselect;
+
+    /* Translate CSR number for VS-mode */
+    csrno = aia_xlate_vs_csrno(env, csrno);
+
+    /* Find the iselect CSR based on CSR number */
+    switch (csrno) {
+    case CSR_MISELECT:
+        iselect = &env->miselect;
+        break;
+    case CSR_SISELECT:
+        iselect = &env->siselect;
+        break;
+    case CSR_VSISELECT:
+        iselect = &env->vsiselect;
+        break;
+    default:
+         return RISCV_EXCP_ILLEGAL_INST;
+    };
+
+    if (val) {
+        *val = *iselect;
+    }
+
+    wr_mask &= ISELECT_MASK;
+    if (wr_mask) {
+        *iselect = (*iselect & ~wr_mask) | (new_val & wr_mask);
+    }
+
+    return RISCV_EXCP_NONE;
+}
+
+static int rmw_iprio(target_ulong xlen,
+                     target_ulong iselect, uint8_t *iprio,
+                     target_ulong *val, target_ulong new_val,
+                     target_ulong wr_mask, int ext_irq_no)
+{
+    int i, firq, nirqs;
+    target_ulong old_val;
+
+    if (iselect < ISELECT_IPRIO0 || ISELECT_IPRIO15 < iselect) {
+        return -EINVAL;
+    }
+    if (xlen != 32 && iselect & 0x1) {
+        return -EINVAL;
+    }
+
+    nirqs = 4 * (xlen / 32);
+    firq = ((iselect - ISELECT_IPRIO0) / (xlen / 32)) * (nirqs);
+
+    old_val = 0;
+    for (i = 0; i < nirqs; i++) {
+        old_val |= ((target_ulong)iprio[firq + i]) << (IPRIO_IRQ_BITS * i);
+    }
+
+    if (val) {
+        *val = old_val;
+    }
+
+    if (wr_mask) {
+        new_val = (old_val & ~wr_mask) | (new_val & wr_mask);
+        for (i = 0; i < nirqs; i++) {
+            /*
+             * M-level and S-level external IRQ priority always read-only
+             * zero. This means default priority order is always preferred
+             * for M-level and S-level external IRQs.
+             */
+            if ((firq + i) == ext_irq_no) {
+                continue;
+            }
+            iprio[firq + i] = (new_val >> (IPRIO_IRQ_BITS * i)) & 0xff;
+        }
+    }
+
+    return 0;
+}
+
+static int rmw_xireg(CPURISCVState *env, int csrno, target_ulong *val,
+                     target_ulong new_val, target_ulong wr_mask)
+{
+    bool virt;
+    uint8_t *iprio;
+    int ret = -EINVAL;
+    target_ulong priv, isel, vgein;
+
+    /* Translate CSR number for VS-mode */
+    csrno = aia_xlate_vs_csrno(env, csrno);
+
+    /* Decode register details from CSR number */
+    virt = false;
+    switch (csrno) {
+    case CSR_MIREG:
+        iprio = env->miprio;
+        isel = env->miselect;
+        priv = PRV_M;
+        break;
+    case CSR_SIREG:
+        iprio = env->siprio;
+        isel = env->siselect;
+        priv = PRV_S;
+        break;
+    case CSR_VSIREG:
+        iprio = env->hviprio;
+        isel = env->vsiselect;
+        priv = PRV_S;
+        virt = true;
+        break;
+    default:
+         goto done;
+    };
+
+    /* Find the selected guest interrupt file */
+    vgein = (virt) ? get_field(env->hstatus, HSTATUS_VGEIN) : 0;
+
+    if (ISELECT_IPRIO0 <= isel && isel <= ISELECT_IPRIO15) {
+        /* Local interrupt priority registers not available for VS-mode */
+        if (!virt) {
+            ret = rmw_iprio(riscv_cpu_mxl_bits(env),
+                            isel, iprio, val, new_val, wr_mask,
+                            (priv == PRV_M) ? IRQ_M_EXT : IRQ_S_EXT);
+        }
+    } else if (ISELECT_IMSIC_FIRST <= isel && isel <= ISELECT_IMSIC_LAST) {
+        /* IMSIC registers only available when machine implements it. */
+        if (env->aia_ireg_rmw_fn[priv]) {
+            /* Selected guest interrupt file should not be zero */
+            if (virt && (!vgein || env->geilen < vgein)) {
+                goto done;
+            }
+            /* Call machine specific IMSIC register emulation */
+            ret = env->aia_ireg_rmw_fn[priv](env->aia_ireg_rmw_fn_arg[priv],
+                                    AIA_MAKE_IREG(isel, priv, virt, vgein,
+                                                  riscv_cpu_mxl_bits(env)),
+                                    val, new_val, wr_mask);
+        }
+    }
+
+done:
+    if (ret) {
+        return (riscv_cpu_virt_enabled(env) && virt) ?
+               RISCV_EXCP_VIRT_INSTRUCTION_FAULT : RISCV_EXCP_ILLEGAL_INST;
+    }
+    return RISCV_EXCP_NONE;
+}
+
 static RISCVException read_mtvec(CPURISCVState *env, int csrno,
                                  target_ulong *val)
 {
@@ -2760,6 +2923,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_MTVAL]    = { "mtval",    any,  read_mtval,    write_mtval    },
     [CSR_MIP]      = { "mip",      any,  NULL,    NULL, rmw_mip        },
 
+    /* Machine-Level Window to Indirectly Accessed Registers (AIA) */
+    [CSR_MISELECT] = { "miselect", aia_any,   NULL, NULL,    rmw_xiselect },
+    [CSR_MIREG]    = { "mireg",    aia_any,   NULL, NULL,    rmw_xireg },
+
     /* Machine-Level Interrupts (AIA) */
     [CSR_MTOPI]    = { "mtopi",    aia_any,   read_mtopi },
 
@@ -2792,6 +2959,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     /* Supervisor Protection and Translation */
     [CSR_SATP]     = { "satp",     smode, read_satp,    write_satp      },
 
+    /* Supervisor-Level Window to Indirectly Accessed Registers (AIA) */
+    [CSR_SISELECT]   = { "siselect",   aia_smode, NULL, NULL, rmw_xiselect },
+    [CSR_SIREG]      = { "sireg",      aia_smode, NULL, NULL, rmw_xireg },
+
     /* Supervisor-Level Interrupts (AIA) */
     [CSR_STOPI]      = { "stopi",      aia_smode, read_stopi },
 
@@ -2833,6 +3004,12 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_HVIPRIO1]    = { "hviprio1",    aia_hmode, read_hviprio1,   write_hviprio1 },
     [CSR_HVIPRIO2]    = { "hviprio2",    aia_hmode, read_hviprio2,   write_hviprio2 },
 
+    /*
+     * VS-Level Window to Indirectly Accessed Registers (H-extension with AIA)
+     */
+    [CSR_VSISELECT]   = { "vsiselect",   aia_hmode, NULL, NULL,      rmw_xiselect },
+    [CSR_VSIREG]      = { "vsireg",      aia_hmode, NULL, NULL,      rmw_xireg },
+
     /* VS-Level Interrupts (H-extension with AIA) */
     [CSR_VSTOPI]      = { "vstopi",      aia_hmode, read_vstopi },