Re: [RFC][PATCH 0/8] x86/mm: Simplify PAE page table handling

[Joerg Roedel <joro@8bytes.org>]

On Fri, Jan 24, 2025 at 11:12:45AM -0800, Dave Hansen wrote:
> Probably INTEL_QUARK_X1000, but it was mostly a toy. It's family 5, so
> this applies:
> 
> static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
> ...
>         VULNWL(INTEL,   5, X86_MODEL_ANY,       NO_SPECULATION),
> 
> Here's one that was released in 2015, probably just for embedded use:
> 
> > https://www.intel.com/content/www/us/en/products/sku/91947/intel-quark-microcontroller-d2000/specifications.html 
> 
> There were some Atoms in 2008 that seem to have had the 64-bit support
> fused off. They were probably the last normal CPU that someone would
> have in a PC that didn't have 64-bit support.
> 
> > https://www.intel.com/content/www/us/en/ark/products/codename/24976/products-formerly-silverthorne.html
> > https://www.intel.com/content/www/us/en/products/sku/36331/intel-atom-processor-n270-512k-cache-1-60-ghz-533-mhz-fsb/specifications.html
> 
> But these are also NO_SPECULATION, so don't need most of the mitigations.

So the last 32bit-only CPUs were released roughly 10 years ago. Most of
these systems are likely out-of-service already, and those still in
service are unlikely to require a new kernel.

Imho it is time to deprecate 32-bit x86 support and set a hard removal
date of, say, end of 2026 or so. It can also be timed to happen after a
long-term stable kernel is released to give the few people who still
want support some more time. This would send a serious message to
hardware vendors to not come up with any more of these pieces.

Btw, I've just built an x86-32 defconfig kernel from the latest tree,
the text section alone is more than 14MiB big, the vmlinux image more
than 29MiB. This is not really suitable for embedded environments.

Regards,

	Joerg