On Wed, 07 Aug 2019 10:54:52 PDT (-0700), alistai...@gmail.com wrote:
On Wed, Aug 7, 2019 at 8:00 AM Palmer Dabbelt <pal...@sifive.com> wrote:
The ISA strings we're providing from QEMU aren't actually legal RISC-V
ISA strings, as both the S and U extensions cannot exist as
single-letter extensions and must instead be multi-letter strings.
We're still using the ISA strings inside QEMU to track the availiable
s/availiable/available/g
extensions, so this patch just strips out the S and U extensions when
formatting ISA strings.
Atish and I were talking about this and we concluded that S and U
aren't extensions, but should be reported in the misa CSR.
Andrew agrees.
This boots Linux on top of 4.1-rc3, which no longer has the U extension
in /proc/cpuinfo.
Signed-off-by: Palmer Dabbelt <pal...@sifive.com>
---
This is another late one, but I'd like to target it for 4.1 as we're
providing illegal ISA strings and I don't want to bake that into a bunch
of other code.
---
target/riscv/cpu.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index f8d07bd20ad7..4df14433d789 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -501,7 +501,22 @@ char *riscv_isa_string(RISCVCPU *cpu)
char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
for (i = 0; i < sizeof(riscv_exts); i++) {
if (cpu->env.misa & RV(riscv_exts[i])) {
- *p++ = qemu_tolower(riscv_exts[i]);
+ char lower = qemu_tolower(riscv_exts[i]);
+ switch (lower) {
+ case 's':
+ case 'u':
+ /*
+ * The 's' and 'u' extensions shouldn't be passed in the device
+ * tree, but we still use them internally to track extension
+ * sets. Here we just explicitly remove them when formatting
+ * an ISA string.
This should be updated to note mention 's' and 'u' as extensions, but
clarify that they are correctly include in the misa CSR.
I'll send a v2 that cleans up the wording on the comment and commit message.
Alistair
+ */
+ break;
+
+ default:
+ *p++ = qemu_tolower(riscv_exts[i]);
+ break;
+ }
}
}
*p = '\0';
--
2.21.0