From: Anup Patel <anup.pa...@wdc.com>
To facilitate software development of RISC-V systems with large number
of HARTs, we increase the maximum number of allowed CPUs to 512 (2^9).
We also add a detailed source level comments about limit defines which
impact the physical address space utilization.
Signed-off-by: Anup Patel <anup.pa...@wdc.com>
Signed-off-by: Anup Patel <a...@brainfault.org>
Reviewed-by: Alistair Francis <alistair.fran...@wdc.com>
Reviewed-by: Frank Chang <frank.ch...@sifive.com>
Message-id: 20220204174700.534953-24-a...@brainfault.org
Signed-off-by: Alistair Francis <alistair.fran...@wdc.com>
---
include/hw/riscv/virt.h | 2 +-
hw/riscv/virt.c | 10 ++++++++++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/include/hw/riscv/virt.h b/include/hw/riscv/virt.h
index d248d0dfa0..78b058ec86 100644
--- a/include/hw/riscv/virt.h
+++ b/include/hw/riscv/virt.h
@@ -24,7 +24,7 @@
#include "hw/block/flash.h"
#include "qom/object.h"
-#define VIRT_CPUS_MAX_BITS 3
+#define VIRT_CPUS_MAX_BITS 9
#define VIRT_CPUS_MAX (1 << VIRT_CPUS_MAX_BITS)
#define VIRT_SOCKETS_MAX_BITS 2
#define VIRT_SOCKETS_MAX (1 << VIRT_SOCKETS_MAX_BITS)
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index c02710f711..7d5f1e58c9 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -45,6 +45,16 @@
#include "hw/pci-host/gpex.h"
#include "hw/display/ramfb.h"
+/*
+ * The virt machine physical address space used by some of the devices
+ * namely ACLINT, PLIC, APLIC, and IMSIC depend on number of Sockets,
+ * number of CPUs, and number of IMSIC guest files.
+ *
+ * Various limits defined by VIRT_SOCKETS_MAX_BITS, VIRT_CPUS_MAX_BITS,
+ * and VIRT_IRQCHIP_MAX_GUESTS_BITS are tuned for maximum utilization
+ * of virt machine physical address space.
+ */
+
#define VIRT_IMSIC_GROUP_MAX_SIZE (1U << IMSIC_MMIO_GROUP_MIN_SHIFT)
#if VIRT_IMSIC_GROUP_MAX_SIZE < \
IMSIC_GROUP_SIZE(VIRT_CPUS_MAX_BITS, VIRT_IRQCHIP_MAX_GUESTS_BITS)
--
2.34.1
