On 6/23/2025 7:04 PM, H. Peter Anvin wrote:
On June 23, 2025 10:40:59 AM PDT, Xin Li <xin@xxxxxxxxx> wrote:
On 6/20/2025 5:50 PM, H. Peter Anvin wrote:
On 2025-06-20 17:45, H. Peter Anvin wrote:
But I simply hate adding a disabled feature that depends on !X86_64;
x86_64 has a broad scope, and new CPU features are often intentionally
not enabled for 32-bit.
(X86_DISABLED_FEATURE_PCID is the only one before LASS)
More importantly, it is wrong.
The 32-bit build can depend on this feature not existing, therefore it SHOULD be listed as a disabled feature.
Ok, that was word salad. What I meant was that the original patch is correct, and we SHOULD have this as a disabled feature.
Agreed!
The reason is that it reduces the need to explicitly test for 32/64 bits for features that don't exist on 32 bits. When they are flagged as disabled, they get filtered out *at compile time*.
It's better to make it depend on X86_32 directly rather than !X86_64:
config X86_DISABLED_FEATURE_LASS
def_bool y
depends on X86_32
But the disabled feature list due to lack of 32-bit enabling will keep
growing until we remove 32-bit kernel code.
Wondering should we bother enforcing cpuid_deps[] on 32-bit?
IOW, turn off the feature when its dependency isn’t satisfied on 32b-it;
don’t just throw a warning and hope for the best.
Thanks!
Xin
We should have the dependencies enforced; in fact, preferably we would enforce them at build time as well.
Yeah, sounds something we can do later :)
