Re: [Xen-devel] [PATCH v9 1/8] VMX: Permanently assign PI hook vmx_pi_switch_to()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.02.17 at 02:45, <chao.gao@xxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -260,9 +260,15 @@ void vmx_pi_hooks_deassign(struct domain *d)
>  
>      ASSERT(d->arch.hvm_domain.pi_ops.vcpu_block);
>  
> +    /*
> +     * Note that we don't set 'd->arch.hvm_domain.pi_ops.switch_to' to NULL
> +     * here. If we deassign the hooks while the vCPU is runnable in the
> +     * runqueue with 'SN' set, all the future notification event will be
> +     * suppressed. Preserving the 'switch_to' hook function can make sure
> +     * event time the vCPU is running the 'SN' field is cleared.
> +     */

Did we now lose the remark indicating that at least in theory
we could remove the hook after it had run one more time? It's
also not really becoming clear why SN continues to matter
after device removal, but perhaps that's just because of my
so far limited understanding of PI.

Also I think you mean "every time" on the last line, albeit that
(as per my remark above) is irrelevant - we need it to run just
once more.

Jan


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