mb/emulation/qemu-riscv: Add support for 512 harts

QEMU has a maximum of 512 of emulated harts supported.

Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: I149c8d8a43733c8ba3e02a84b0a3606d98f8b2c1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81083
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Reviewed-by: Alicja Michalska <ahplka19@gmail.com>
Reviewed-by: Carlos López <carlos.lopezr4096@gmail.com>

src/commonlib/Makefile.mk

@@ -32,6 +32,7 @@ romstage-$(CONFIG_PLATFORM_USES_FSP2_0) += fsp_relocate.c
 endif
 ramstage-$(CONFIG_PLATFORM_USES_FSP2_0) += fsp_relocate.c
 
+bootblock-$(CONFIG_FLATTENED_DEVICE_TREE) += device_tree.c
 romstage-$(CONFIG_FLATTENED_DEVICE_TREE) += device_tree.c
 ramstage-$(CONFIG_FLATTENED_DEVICE_TREE) += device_tree.c
 

src/mainboard/emulation/qemu-riscv/Kconfig

@@ -26,6 +26,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select FLATTENED_DEVICE_TREE
 	select MISSING_BOARD_RESET
 	select DRIVERS_UART_8250MEM
+	select RISCV_GET_HART_COUNT_AT_RUNTIME
 	select RISCV_HAS_OPENSBI
 	select ARCH_RISCV_S
 	select ARCH_RISCV_U
@@ -35,6 +36,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select ARCH_ROMSTAGE_RISCV
 	select ARCH_RAMSTAGE_RISCV
 	select RISCV_USE_ARCH_TIMER
+	select FLATTENED_DEVICE_TREE
 
 config MEMLAYOUT_LD_FILE
 	string
@@ -48,7 +50,7 @@ config MAINBOARD_PART_NUMBER
 
 config MAX_CPUS
 	int
-	default 1
+	default 512 # QEMUs current limit for the virt target
 
 config RISCV_ARCH
 	string

src/mainboard/emulation/qemu-riscv/Makefile.mk

@@ -4,12 +4,14 @@ bootblock-y += mainboard.c
 bootblock-y += uart.c
 bootblock-y += rom_media.c
 bootblock-y += clint.c
+bootblock-y += smp.c
 
 romstage-y += cbmem.c
 romstage-y += romstage.c
 romstage-y += uart.c
 romstage-y += rom_media.c
 romstage-y += clint.c
+romstage-y += smp.c
 
 ramstage-y += mainboard.c
 ramstage-y += uart.c
@@ -17,5 +19,6 @@ ramstage-y += rom_media.c
 ramstage-y += clint.c
 ramstage-y += cbmem.c
 ramstage-y += chip.c
+ramstage-y += smp.c
 
 CPPFLAGS_common += -I$(src)/mainboard/$(MAINBOARDDIR)/include

src/mainboard/emulation/qemu-riscv/memlayout.ld

@@ -16,5 +16,5 @@ SECTIONS
 	PRERAM_CBMEM_CONSOLE(QEMU_VIRT_DRAM + 128K + 256K + 256K + 2M,  8K)
 	FMAP_CACHE(QEMU_VIRT_DRAM + 128K + 256K + 256K + 2M + 8K,  2K)
 	CBFS_MCACHE(QEMU_VIRT_DRAM + 128K + 256K + 256K + 2M + 8K + 2K,  10K)
-	STACK(QEMU_VIRT_DRAM + 128K + 256K + 256K + 2M + 8K + 2K + 10K, 4M)
+	STACK(QEMU_VIRT_DRAM + 128K + 256K + 256K + 2M + 8K + 2K + 10K, 4K * CONFIG_MAX_CPUS)
 }

src/mainboard/emulation/qemu-riscv/smp.c

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <mcall.h>
+#include <arch/smp/smp.h>
+#include <commonlib/device_tree.h>
+#include <console/console.h>
+
+unsigned int smp_get_hart_count(void)
+{
+	if (!fdt_is_valid(HLS()->fdt))
+		goto error;
+
+	uint32_t cpus_offset = fdt_find_node_by_path(HLS()->fdt, "/cpus", NULL, NULL);
+	if (!cpus_offset)
+		goto error;
+
+	static u32 harts[CONFIG_MAX_CPUS]; // too big for the stack
+	size_t count_harts = fdt_find_subnodes_by_prefix(HLS()->fdt, cpus_offset, "cpu@",
+							 NULL, NULL, harts, CONFIG_MAX_CPUS);
+	if (!count_harts)
+		goto error;
+
+	printk(BIOS_DEBUG, "found %zu harts in devicetree\n", count_harts);
+	return count_harts;
+error:
+	printk(BIOS_ERR, "%s: Failed to read devicetree to get number of harts\n", __func__);
+	return 1; // Return single hart on failure to keep booting
+}