[PATCHv2] arm64/cpufeature: don't use mutex in bringup path
Mark Rutland
mark.rutland at arm.com
Thu May 11 08:37:20 PDT 2017
On Thu, May 11, 2017 at 04:15:38PM +0100, Suzuki K Poulose wrote:
> On 11/05/17 16:01, Mark Rutland wrote:
> >+static inline bool cpus_have_const_cap(int num)
> >+{
> >+ if (static_branch_likely(&arm64_const_caps_ready))
> >+ return __cpus_have_const_cap(num);
> >+ else
> >+ return cpus_have_cap(num);
>
> We use cpus_have_const_cap() from hyp code, via has_vhe() and we could potentially
> try to access unmapped kernel data from hyp if we fallback to cpus_have_cap().
> However, it looks like we have already set arm64_const_caps_ready, so should not
> hit it in practise. May be we could add a stricter version of the helper ?
>
> static inline cpus_have_const_cap_strict(int num)
> {
> BUG_ON(!static_branch_likely(&arm64_const_caps_ready);
> return __cpus_have_const_cap(num);
> }
Just to check, is that the only user of cpus_have_const_cap() at hyp?
If so, I can do something like the above, patching <asm/virt.h> to use
it for has_vhe().
We don't have a BUG handler at hyp, but that should trigger a hyp panic,
which I guess is good enough.
Marc, thoughts?
Thanks,
Mark.
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