Re: [PATCH v2 2/3] x86/cpu/intel: Simplify F00F bug notice using pr_notice_once()

[Maciej W. Rozycki]

On Tue, 26 May 2026, H. Peter Anvin wrote:

> > Yes, 32-bit x86 remains a supported target with the GNU C library, down 
> >to i486 I believe, that includes dedicated platform code such as for the 
> >80-bit extended format, so this was a good portability exercise, given 
> >that the scope of the tests were floating-point formatted input/output 
> >specifiers, not previously sufficiently covered.
> 
> However, x87 should be testable on any x86 silicon.

 We have model-dependent quirks, clearly.  Actually even this system is 
not pure x87 anymore as it has the MMX extension, and with the recent 
removal of i486 support it's getting harder and harder to get at the right 
environment.  As we spoke IIRC last year, I'll try to maintain support for 
the i486 with emulation off-tree.  The hard part might be RDTSC.

 And I've seen cases of code relying on newer hardware features by chance, 
which then eventually broke when tried on original hardware.  I've seen 
and fixed QEMU bugs too where ISA subsetting wasn't correct and software 
that worked on QEMU broke on real hw.

 Then haven't more recent x86 architecture revisions switched away from 
the venerable x87 FPU and its data formats for FP computations?  A genuine 
question as I have not been following progress here.  What I know though 
is the x87 stack architecture is antiquated, and hard to pipeline and emit 
optimised code for.  And also mixing computations of various precisions is 
problematic.

  Maciej