Messages in this thread | | | Date | Thu, 11 May 2017 16:42:19 +0100 | From | Mark Rutland <> | Subject | Re: [PATCHv2] arm64/cpufeature: don't use mutex in bringup path |
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On Thu, May 11, 2017 at 04:37:20PM +0100, Mark Rutland wrote: > 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?
The other option, given this is *only* used at hyp, is:
static inline bool has_vhe(void) { return !!(read_sysreg(HCR_EL2) & HCR_E2H); }
... though I assume we may have avoided that deliberately.
Thanks, Mark.
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