Re: [Xen-devel] [PATCH v7 1/6] VMX: Permanently assign PI hook vmx_pi_switch_to()

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Nov 07, 2016 at 04:07:58PM +0800, Feng Wu wrote:
> PI hook vmx_pi_switch_to() is needed even when any previously
> assigned device is detached from the domain. Since 'SN' bit is
> also used to control the CPU side PI and we change the state of
> SN bit in these two functions, then evaluate this bit in
> vmx_deliver_posted_intr() when trying to deliver the interrupt
> in posted way via software. The problem is if we deassign the
> hooks while the vCPU is runnable in the runqueue with 'SN' set,
> all the furture notificaton event will be suppressed. This patch
> makes the hook permanently assigned.
> 
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> ---
> v7:
> - comments changes.
> 
> v6:
> - Adjust the comments and wording.
> 
> v5:
> - Zap "pi_switch_from" hook
> 
> v4:
> - Don't zap vmx_pi_switch_from() and vmx_pi_switch_to() when
> any previously assigned device is detached from the domain.
> - Comments changes.
> 
>  xen/arch/x86/hvm/vmx/vmx.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 3d330b6..10546af 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -222,8 +222,13 @@ void vmx_pi_hooks_deassign(struct domain *d)
>  
>      d->arch.hvm_domain.vmx.vcpu_block = NULL;
>      d->arch.hvm_domain.vmx.pi_switch_from = NULL;
> -    d->arch.hvm_domain.vmx.pi_switch_to = NULL;
>      d->arch.hvm_domain.vmx.pi_do_resume = NULL;
> +
> +    /*
> +     * In fact, we could remove 'vmx_pi_switch_to' inside itself if no new 
> device

I am having a hard time parsing that. What is the 'inside itself'?

Otherwise,
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> +     * is in the process of getting assigned and "from" hook is NULL. 
> However,
> +     * it is not straightforward to find a clear solution, so just leave it 
> here.
> +     */
>  }
>  
>  static int vmx_domain_initialise(struct domain *d)
> -- 
> 2.1.0
> 
> 
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