[PATCH] hw/riscv: virt: Enable booting M-mode or S-mode FW from pflash0

[Sunil V L]

Currently, virt machine supports two pflash instances each with
32MB size. However, the first pflash is always assumed to
contain M-mode firmware and reset vector is set to this if
enabled. Hence, for S-mode payloads like EDK2, only one pflash
instance is available for use. This means both code and NV variables
of EDK2 will need to use the same pflash.

The OS distros keep the EDK2 FW code as readonly. When non-volatile
variables also need to share the same pflash, it is not possible
to keep it as readonly since variables need write access.

To resolve this issue, the code and NV variables need to be separated.
But in that case we need an extra flash. Hence, modify the convention
such that pflash0 will contain the M-mode FW only when "-bios none"
option is used. Otherwise, pflash0 will contain the S-mode payload FW.
This enables both pflash instances available for EDK2 use.

Example usage:
1) pflash0 containing M-mode FW
qemu-system-riscv64 -bios none -pflash <mmode_fw> -machine virt
or
qemu-system-riscv64 -bios none \
-drive file=<mmode_fw>,if=pflash,format=raw,unit=0 -machine virt

2) pflash0 containing S-mode payload like EDK2
qemu-system-riscv64 -pflash <smode_fw_code> -pflash <smode_vars> -machine  virt
or
qemu-system-riscv64 -bios <opensbi_fw> \
-pflash <smode_fw_code> \
-pflash <smode_vars> \
-machine  virt
or
qemu-system-riscv64 -bios <opensbi_fw> \
-drive file=<smode_fw_code>,if=pflash,format=raw,unit=0,readonly=on \
-drive file=<smode_fw_vars>,if=pflash,format=raw,unit=1 \
-machine virt

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
---
 hw/riscv/virt.c | 51 ++++++++++++++++++-------------------------------
 1 file changed, 19 insertions(+), 32 deletions(-)

diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 4e3efbee16..1187a60d6e 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -1245,7 +1245,7 @@ static void virt_machine_done(Notifier *notifier, void 
*data)
     target_ulong firmware_end_addr, kernel_start_addr;
     const char *firmware_name = riscv_default_firmware_name(&s->soc[0]);
     uint32_t fdt_load_addr;
-    uint64_t kernel_entry;
+    uint64_t kernel_entry = 0;
 
     /*
      * Only direct boot kernel is currently supported for KVM VM,
@@ -1266,42 +1266,29 @@ static void virt_machine_done(Notifier *notifier, void 
*data)
     firmware_end_addr = riscv_find_and_load_firmware(machine, firmware_name,
                                                      start_addr, NULL);
 
-    if (drive_get(IF_PFLASH, 0, 1)) {
-        /*
-         * S-mode FW like EDK2 will be kept in second plash (unit 1).
-         * When both kernel, initrd and pflash options are provided in the
-         * command line, the kernel and initrd will be copied to the fw_cfg
-         * table and opensbi will jump to the flash address which is the
-         * entry point of S-mode FW. It is the job of the S-mode FW to load
-         * the kernel and initrd using fw_cfg table.
-         *
-         * If only pflash is given but not -kernel, then it is the job of
-         * of the S-mode firmware to locate and load the kernel.
-         * In either case, the next_addr for opensbi will be the flash address.
-         */
-        riscv_setup_firmware_boot(machine);
-        kernel_entry = virt_memmap[VIRT_FLASH].base +
-                       virt_memmap[VIRT_FLASH].size / 2;
-    } else if (machine->kernel_filename) {
+    if (drive_get(IF_PFLASH, 0, 0)) {
+        if (machine->firmware && !strcmp(machine->firmware, "none")) {
+            /*
+             * Pflash was supplied but bios is none, let's overwrite the
+             * address we jump to after reset to the base of the flash.
+             */
+            start_addr = virt_memmap[VIRT_FLASH].base;
+        } else {
+            /*
+             * Pflash was supplied but bios is not none. In this case,
+             * base of the flash would contain S-mode payload.
+             */
+            riscv_setup_firmware_boot(machine);
+            kernel_entry = virt_memmap[VIRT_FLASH].base;
+        }
+    }
+
+    if (machine->kernel_filename && !kernel_entry) {
         kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
                                                          firmware_end_addr);
 
         kernel_entry = riscv_load_kernel(machine, &s->soc[0],
                                          kernel_start_addr, true, NULL);
-    } else {
-       /*
-        * If dynamic firmware is used, it doesn't know where is the next mode
-        * if kernel argument is not set.
-        */
-        kernel_entry = 0;
-    }
-
-    if (drive_get(IF_PFLASH, 0, 0)) {
-        /*
-         * Pflash was supplied, let's overwrite the address we jump to after
-         * reset to the base of the flash.
-         */
-        start_addr = virt_memmap[VIRT_FLASH].base;
     }
 
     fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM].base,
-- 
2.34.1