On Fri, Apr 12, 2024 at 11:22 AM Charlie Jenkins charlie@rivosinc.com wrote:
On Fri, Apr 12, 2024 at 10:04:42AM -0700, Evan Green wrote:
On Fri, Apr 12, 2024 at 4:35 AM Conor Dooley conor.dooley@microchip.com wrote:
On Thu, Apr 11, 2024 at 09:11:20PM -0700, Charlie Jenkins wrote:
Ensure that hwprobe does not flag "v" when xtheadvector is present.
Signed-off-by: Charlie Jenkins charlie@rivosinc.com
arch/riscv/kernel/sys_hwprobe.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c index 8cae41a502dd..e0a42c851511 100644 --- a/arch/riscv/kernel/sys_hwprobe.c +++ b/arch/riscv/kernel/sys_hwprobe.c @@ -69,7 +69,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair, if (riscv_isa_extension_available(NULL, c)) pair->value |= RISCV_HWPROBE_IMA_C;
if (has_vector())
if (has_vector() && !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR))Hmm, I think this is "dangerous". has_vector() is used across the kernel now in several places for the in-kernel vector. I don't think that has_vector() should return true for the T-Head stuff given that & has_vector() should represent the ratified spec. I'll have to think about this one and how nasty this makes any of the save/restore code etc.
Yeah, my nose crinkled here as well. If you're having to do a vendorish thing in this generic spot, then others may too, suggesting perhaps this isn't the cleanest way to go about it. Ideally extensions are all additive, rather than subtractive, I guess?
This was the "easiest" way to support this but I agree this is not ideal. The vector code is naturally coupled with having support for "v" and I wanted to leverage that. The other concern is all of the ifdefs for having V enabled. I can make all of those V or XTHEADVECTOR; that will increase the surface area of xtheadvector but it is probably the right(?) way to go.
For the ifdefs, if you've got a Kconfig somewhere for THEAD_VECTOR, can't that just depend on the V config? We'd end up with the limitation that you can't add V 0.7 support without also dragging in V1.0 support, but that's probably fine, right?
-Evan