powerpc: Add an inline function to update HID0
mpe at ellerman.id.au
Tue Aug 4 20:08:58 AEST 2015
On Tue, 2015-04-08 at 08:30:58 UTC, "Gautham R. Shenoy" wrote:
> Section 3.7 of Version 1.2 of the Power8 Processor User's Manual
> prescribes that updates to HID0 be preceded by a SYNC instruction and
> followed by an ISYNC instruction (Page 91).
> Create a function name update_hid0() which follows this recipe and
> invoke it from the static split core path.
> Signed-off-by: Gautham R. Shenoy <ego at linux.vnet.ibm.com>
> arch/powerpc/include/asm/kvm_ppc.h | 11 +++++++++++
Why is it in there? It's not KVM related per se.
Where should it go? I think reg.h would be best, ideally near the definition
for HID0, though that's probably not possible because of ASSEMBLY requirements.
So at the bottom of reg.h ?
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index c6ef05b..325f1d6 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -685,4 +685,15 @@ static inline ulong kvmppc_get_ea_indexed(struct kvm_vcpu *vcpu, int ra, int rb)
> extern void xics_wake_cpu(int cpu);
> +static inline void update_hid0(unsigned long hid0)
> + /*
> + * The HID0 update should at the very least be preceded by a
> + * a SYNC instruction followed by an ISYNC instruction
> + */
> + mb();
> + mtspr(SPRN_HID0, hid0);
> + isync();
That's going to turn into three separate inline asm blocks, which is maybe a
bit unfortunate. Have you checked the generated code is what we want, ie. just
sync, mtspr, isync ?
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