Re: [PATCH v3] lib/raid/xor: x86: Add AVX-512 optimized xor_gen()
Borislav Petkov <[email protected]>
| Newsgroups | gmane.linux.kernel.cryptoapi,gmane.linux.raid,gmane.linux.kernel |
|---|---|
| Message-ID | <[email protected]> |
On June 15, 2026 8:10:50 PM UTC, Eric Biggers <[email protected]> wrote: > >But I wanted to ask: do we really care about the case where features are >"supported" but their XCR0 bits aren't set? Perhaps the kernel just >doesn't/shouldn't support weird cases like "-cpu max,xsave=off"? > Yes, our aim is to support only configurations which are actually present in real hardware and not a "oh, it would be good if it did that, just because..." >If this case indeed needs to be handled, could we make things easier for >the kernel's AVX and AVX-512 optimized code? Currently AVX-512 needs: > > if (boot_cpu_has(X86_FEATURE_AVX512F) && > cpu_has_xfeatures(XFEATURE_MASK_FP | XFEATURE_MASK_SSE | > XFEATURE_MASK_YMM | XFEATURE_MASK_AVX512, NULL)) > >How about we make X86_FEATURE_AVX512F depend on XCR0=111xx111, and >X86_FEATURE_AVX depend on XCR0=xxxxx111? Then the cpu_has_xfeatures() >check wouldn't be needed. Is there any reason not to do that? How do you want to accomplish that? Very early during boot on the BSP you sanity-check XCR0 and clear feature flags if components are not set? Thx. -- Small device. Typos and formatting crap