Re: [PATCH 2/5] KVM: Implement CR read caching for KVM paravirt_ops

Avi Kivity
2007-06-18T08:11:33Z

Anthony Liguori wrote:
> +/*
> + * Control register reads can be trapped. Since trapping is relatively
> + * expensive, we can avoid paying the cost by caching logically.
> + */
> +static unsigned long kvm_read_cr(int reg)
> +{
> + struct kvm_paravirt_state *state
> + = per_cpu(paravirt_state, smp_processor_id());
> +
> + if (unlikely(!state->cr_valid[reg])) {
> + if (reg == 0)
> + state->cached_cr[reg] = native_read_cr0();
> + else if (reg == 3)
> + state->cached_cr[reg] = native_read_cr3();
> + else if (reg == 4)
> + state->cached_cr[reg] = native_read_cr4();
> + else
> + BUG();
> + state->cr_valid[reg] = 1;
> + }
> + return state->cached_cr[reg];
> +}
> +

It would be good to declare this (and kvm_write_cr) always_inline.
These functions are never called with a non-constant reg parameters, and
the unsightly if tree (more readable as a switch, IMO) will fold nicely
when inlined.

--
error compiling committee.c: too many arguments to function