hw/riscv/riscv-iommu: add riscv-iommu-hpm file

The HPM (Hardware Performance Monitor) support consists of almost 7
hundred lines that would be put on top of the base riscv-iommu
emulation.

To avoid clogging riscv-iommu.c, add a separated riscv-iommu-hpm file
that will contain HPM specific code.

We'll start by adding riscv_iommu_hpmcycle_read(), a helper that will be
called during the riscv_iommu_mmio_read() callback.

This change will have no effect on the existing emulation since we're
not declaring HPM feature support.

Signed-off-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250224190826.1858473-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/riscv-iommu-hpm.c

@@ -0,0 +1,54 @@
+/*
+ * RISC-V IOMMU - Hardware Performance Monitor (HPM) helpers
+ *
+ * Copyright (C) 2022-2023 Rivos Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/timer.h"
+#include "cpu_bits.h"
+#include "riscv-iommu-hpm.h"
+#include "riscv-iommu.h"
+#include "riscv-iommu-bits.h"
+#include "trace.h"
+
+/* For now we assume IOMMU HPM frequency to be 1GHz so 1-cycle is of 1-ns. */
+static inline uint64_t get_cycles(void)
+{
+    return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+}
+
+uint64_t riscv_iommu_hpmcycle_read(RISCVIOMMUState *s)
+{
+    const uint64_t cycle = riscv_iommu_reg_get64(
+        s, RISCV_IOMMU_REG_IOHPMCYCLES);
+    const uint32_t inhibit = riscv_iommu_reg_get32(
+        s, RISCV_IOMMU_REG_IOCOUNTINH);
+    const uint64_t ctr_prev = s->hpmcycle_prev;
+    const uint64_t ctr_val = s->hpmcycle_val;
+
+    if (get_field(inhibit, RISCV_IOMMU_IOCOUNTINH_CY)) {
+        /*
+         * Counter should not increment if inhibit bit is set. We can't really
+         * stop the QEMU_CLOCK_VIRTUAL, so we just return the last updated
+         * counter value to indicate that counter was not incremented.
+         */
+        return (ctr_val & RISCV_IOMMU_IOHPMCYCLES_COUNTER) |
+               (cycle & RISCV_IOMMU_IOHPMCYCLES_OVF);
+    }
+
+    return (ctr_val + get_cycles() - ctr_prev) |
+        (cycle & RISCV_IOMMU_IOHPMCYCLES_OVF);
+}