2018-11-05 14:45+0800, Wei Yang:
> Commit af585b921e5d ("KVM: Halt vcpu if page it tries to access is
> swapped out") introduces async_pf.
>
> The gfn hash table size is defined as:
>
> gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];
>
> And iterations in arch/x86/kvm/x86.c are checked with:
>
> i < roundup_pow_of_two(ASYNC_PF_PER_VCPU)
>
> While the check in kvm_setup_async_pf() is:
>
> if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
>
> Generally this works good, while the check is not exact.
>
> This patch adjust the check in kvm_setup_async_pf() to use the same
> boundary as others.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> virt/kvm/async_pf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index 23c2519c5b32..4f4f6eac88a4 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -182,7 +182,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
> {
> struct kvm_async_pf *work;
>
> - if (vcpu->async_pf.queued >= ASYNC_PF_PER_VCPU)
> + if (vcpu->async_pf.queued >= roundup_pow_of_two(ASYNC_PF_PER_VCPU))
This is actually correct.
Unlike the others in arch/x86, this condition is in general code that
should have no idea about architectural constraints, like
ASYNC_PF_PER_VCPU being a power of two.
It'd be better to change the x86 code to avoid the weird
roundup_pow_of_two() everywhere. I'm thinking about
#define ASYNC_PF_PER_VCPU_ORDER 6
#define ASYNC_PF_PER_VCPU (1 << ASYNC_PF_PER_VCPU)
Thanks.
