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[RFC PATCH 14/16] hw/misc: riscv_wgchecker: Implement correct block-acce


From: Jim Shu
Subject: [RFC PATCH 14/16] hw/misc: riscv_wgchecker: Implement correct block-access behavior
Date: Wed, 12 Jun 2024 16:14:14 +0800

The wgChecker is configurable for whether blocked accesses:
* should cause a bus error or just read return zero and write ignore
* should generate the interrupt or not

Signed-off-by: Jim Shu <jim.shu@sifive.com>
---
 hw/misc/riscv_wgchecker.c | 169 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 167 insertions(+), 2 deletions(-)

diff --git a/hw/misc/riscv_wgchecker.c b/hw/misc/riscv_wgchecker.c
index ab03fd671f..55e5e8127f 100644
--- a/hw/misc/riscv_wgchecker.c
+++ b/hw/misc/riscv_wgchecker.c
@@ -100,6 +100,169 @@ REG32(SLOT_CFG,             0x010)
 #define P_READ                  (1 << 0)
 #define P_WRITE                 (1 << 1)
 
+static void decode_napot(hwaddr a, hwaddr *sa, hwaddr *ea)
+{
+    /*
+     * aaaa...aaa0   8-byte NAPOT range
+     * aaaa...aa01   16-byte NAPOT range
+     * aaaa...a011   32-byte NAPOT range
+     * ...
+     * aa01...1111   2^XLEN-byte NAPOT range
+     * a011...1111   2^(XLEN+1)-byte NAPOT range
+     * 0111...1111   2^(XLEN+2)-byte NAPOT range
+     * 1111...1111   Reserved
+     */
+
+    a = FROM_SLOT_ADDR(a) | 0x3;
+
+    if (sa) {
+        *sa = a & (a + 1);
+    }
+    if (ea) {
+        *ea = a | (a + 1);
+    }
+}
+
+typedef struct WgAccessResult WgAccessResult;
+struct WgAccessResult {
+    bool is_success;
+    bool has_bus_error;
+    bool has_interrupt;
+    uint8_t perm:2;
+};
+
+static WgAccessResult wgc_check_access(
+    RISCVWgCheckerState *s, hwaddr phys_addr, uint32_t wid, bool is_write)
+{
+    WgCheckerSlot *slot, *prev_slot;
+    uint32_t cfg_a, prev_cfg_a;
+    uint64_t start, end;
+    int slot_id, wgc_perm = 0;
+    WgAccessResult result = { 0 };
+
+    bool is_matching = false;
+    bool slot0_be, slot0_ip;
+    bool matched_slot_be = false, matched_slot_ip = false;
+
+    for (slot_id = 0; slot_id < s->slot_count; slot_id++) {
+        slot = &s->slots[slot_id + 1];
+        cfg_a = FIELD_EX32(slot->cfg, SLOT_CFG, A);
+
+        if (cfg_a == A_TOR) {
+            prev_slot = &s->slots[slot_id];
+
+            prev_cfg_a = FIELD_EX32(prev_slot->cfg, SLOT_CFG, A);
+            if (prev_cfg_a == A_NA4) {
+                start = FROM_SLOT_ADDR(prev_slot->addr) + 4;
+            } else if (prev_cfg_a == A_NAPOT) {
+                decode_napot(prev_slot->addr, NULL, &start);
+                start += 1;
+            } else { /* A_TOR or A_OFF */
+                start = FROM_SLOT_ADDR(prev_slot->addr);
+            }
+            end = FROM_SLOT_ADDR(slot->addr);
+        } else if (cfg_a == A_NA4) {
+            start = FROM_SLOT_ADDR(slot->addr);
+            end = start + 4;
+        } else if (cfg_a == A_NAPOT) {
+            decode_napot(slot->addr, &start, &end);
+            end += 1;
+        } else {
+            /* A_OFF: not in slot range. */
+            continue;
+        }
+
+        /* wgChecker slot range is between start to (end - 1). */
+        if ((start <= phys_addr) && (phys_addr < end)) {
+            /* Match the wgC slot */
+            int perm = ((slot->perm >> (wid * 2)) & 0x3);
+
+            /* If any matching rule permits access, the access is permitted. */
+            wgc_perm |= perm;
+
+            /*
+             * If any matching rule wants to report error (IRQ or Bus Error),
+             * the denied access should report error.
+             */
+            is_matching = true;
+            if (is_write) {
+                matched_slot_be |= FIELD_EX64(slot->cfg, SLOT_CFG, EW);
+                matched_slot_ip |= FIELD_EX64(slot->cfg, SLOT_CFG, IW);
+            } else {
+                matched_slot_be |= FIELD_EX64(slot->cfg, SLOT_CFG, ER);
+                matched_slot_ip |= FIELD_EX64(slot->cfg, SLOT_CFG, IR);
+            }
+        }
+    }
+
+    /* If no matching rule, error reporting depends on the slot0's config. */
+    if (is_write) {
+        slot0_be = FIELD_EX64(s->slots[0].cfg, SLOT_CFG, EW);
+        slot0_ip = FIELD_EX64(s->slots[0].cfg, SLOT_CFG, IW);
+    } else {
+        slot0_be = FIELD_EX64(s->slots[0].cfg, SLOT_CFG, ER);
+        slot0_ip = FIELD_EX64(s->slots[0].cfg, SLOT_CFG, IR);
+    }
+
+    result.is_success = is_write ? (wgc_perm & P_WRITE) : (wgc_perm & P_READ);
+    result.perm = wgc_perm;
+    if (!result.is_success) {
+        if (is_matching) {
+            result.has_bus_error = matched_slot_be;
+            result.has_interrupt = matched_slot_ip;
+        } else {
+            result.has_bus_error = slot0_be;
+            result.has_interrupt = slot0_ip;
+        }
+    }
+
+    return result;
+}
+
+static MemTxResult riscv_wgc_handle_blocked_access(
+    WgCheckerRegion *region, hwaddr addr, uint32_t wid, bool is_write)
+{
+    RISCVWgCheckerState *s = RISCV_WGCHECKER(region->wgchecker);
+    bool be, ip;
+    WgAccessResult result;
+    hwaddr phys_addr;
+
+    be = FIELD_EX64(s->errcause, ERRCAUSE, BE);
+    ip = FIELD_EX64(s->errcause, ERRCAUSE, IP);
+    phys_addr = addr + region->region_offset;
+
+    /*
+     * Check if this blocked access trigger IRQ (Bus Error) or not.
+     * It depends on wgChecker slot config (cfg.IR/IW/ER/EW bits).
+     */
+    result = wgc_check_access(s, phys_addr, wid, is_write);
+
+    if (!be && !ip) {
+        /*
+         * With either of the be or ip bits is set, further violations do not
+         * update the errcause or erraddr registers. Also, new interrupts
+         * cannot be generated until the be and ip fields are cleared.
+         */
+        if (result.has_interrupt || result.has_bus_error) {
+            s->errcause = FIELD_DP64(s->errcause, ERRCAUSE, WID, wid);
+            s->errcause = FIELD_DP64(s->errcause, ERRCAUSE, R, !is_write);
+            s->errcause = FIELD_DP64(s->errcause, ERRCAUSE, W, is_write);
+            s->erraddr = TO_SLOT_ADDR(phys_addr);
+        }
+
+        if (result.has_interrupt) {
+            s->errcause = FIELD_DP64(s->errcause, ERRCAUSE, IP, 1);
+            qemu_irq_raise(s->irq);
+        }
+
+        if (result.has_bus_error) {
+            s->errcause = FIELD_DP64(s->errcause, ERRCAUSE, BE, 1);
+        }
+    }
+
+    return result.has_bus_error ? MEMTX_ERROR : MEMTX_OK;
+}
+
 /*
  * Accesses only reach these read and write functions if the wgChecker
  * is blocking them; non-blocked accesses go directly to the downstream
@@ -109,23 +272,25 @@ static MemTxResult riscv_wgc_mem_blocked_read(void 
*opaque, hwaddr addr,
                                                uint64_t *pdata,
                                                unsigned size, MemTxAttrs attrs)
 {
+    WgCheckerRegion *region = opaque;
     uint32_t wid = mem_attrs_to_wid(attrs);
 
     trace_riscv_wgc_mem_blocked_read(addr, size, wid);
 
     *pdata = 0;
-    return MEMTX_OK;
+    return riscv_wgc_handle_blocked_access(region, addr, wid, false);
 }
 
 static MemTxResult riscv_wgc_mem_blocked_write(void *opaque, hwaddr addr,
                                                uint64_t value,
                                                unsigned size, MemTxAttrs attrs)
 {
+    WgCheckerRegion *region = opaque;
     uint32_t wid = mem_attrs_to_wid(attrs);
 
     trace_riscv_wgc_mem_blocked_write(addr, value, size, wid);
 
-    return MEMTX_OK;
+    return riscv_wgc_handle_blocked_access(region, addr, wid, true);
 }
 
 static const MemoryRegionOps riscv_wgc_mem_blocked_ops = {
-- 
2.17.1




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