Re: [PATCH 5.4 2/2] ARM: 9044/1: vfp: use undef hook for VFP support detection

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Mar 16, 2021 at 09:59:18AM -0700, Nick Desaulniers wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> commit 3cce9d44321e460e7c88cdec4e4537a6e9ad7c0d upstream.
> 
> Commit f77ac2e378be9dd6 ("ARM: 9030/1: entry: omit FP emulation for UND
> exceptions taken in kernel mode") failed to take into account that there
> is in fact a case where we relied on this code path: during boot, the
> VFP detection code issues a read of FPSID, which will trigger an undef
> exception on cores that lack VFP support.
> 
> So let's reinstate this logic using an undef hook which is registered
> only for the duration of the initcall to vpf_init(), and which sets
> VFP_arch to a non-zero value - as before - if no VFP support is present.
> 
> Fixes: f77ac2e378be9dd6 ("ARM: 9030/1: entry: omit FP emulation for UND ...")
> Reported-by: "kernelci.org bot" <bot@kernelci.org>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> This is meant to be applied on top of
> https://lore.kernel.org/stable/20210315231952.1482097-1-ndesaulniers@google.com/.
> If it's preferrable to send an .mbox file or a series with cover letter,
> I'm happy to resend it as such, just let me know.

Please resend it that way, makes it easier to figure out what is going
on here...

thanks,

greg k-h