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Initrd not loaded on riscv32
I attempted to run qemu with a ram disk. However, when reading the contents of the disk from within the VM I only get back zeros.
I was able to trace the issue to a mismatch of expectations on line 93 of hw/riscv/virt.c. Specifically, when running in 32-bit mode the value of kernel_entry is sign extended to 64-bits, but load_image_targphys expects the start address to not be sign extended.
Straw man patch (works for 32-bit but would probably break 64-bit VMs?):
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index e7f0716fb6..32216f993c 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -90,7 +90,7 @@ static hwaddr load_initrd(const char *filename, uint64_t mem_size,
* halfway into RAM, and for boards with 256MB of RAM or more we put
* the initrd at 128MB.
*/
- *start = kernel_entry + MIN(mem_size / 2, 128 * MiB);
+ *start = (kernel_entry & 0xffffffff) + MIN(mem_size / 2, 128 * MiB);
size = load_ramdisk(filename, *start, mem_size - *start);
if (size == -1) {
Run command:
$ qemu/build/riscv32-softmmu/qemu-system-riscv32 -machine virt -kernel mykernel.elf -nographic -initrd payload
Commit hash:
3a183e330dbd7dbcac3841737ac874979552cca2
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