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SubjectRe: linux-next: Tree for Mar 25 (arch/x86/kvm/)
On Wed, Mar 25, 2020 at 09:46:06AM -0700, Sean Christopherson wrote:
> On Wed, Mar 25, 2020 at 05:26:20PM +0100, Paolo Bonzini wrote:
> > On 25/03/20 17:14, Sean Christopherson wrote:
> > >> Doh, right. I think the only solution for that one is to degrade it to
> > >> WARN_ON(1).
> > > I reproduced the error, give me a bit to play with the code to see if the
> > > BUILD_BUG can be preserved. I'm curious as to why kvm_cpu_cap_mask() is
> > > special, and why it only fails with this config.
> > >
> >
> > I could not reproduce it, but I would not be surprised if there are
> > other configurations where the compiler cannot constant-propagate from
> > the reverse_cpuid struct into __cpuid_entry_get_reg.
>
> The error is related to UBSAN. There is at least one legitimate (but benign)
> underlying issue. I'm chasing down a second instance of the BUILD_BUG.

Argh, red herring. There is no underlying issue other than gcc tripping up
when -fsanitize=alignment is enabled by UBSAN. Good news is that the build
error can be fixed without resorting to a hack.

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