Re: [Xen-devel] [PATCH v8 1/7] VMX: Permanently assign PI hook vmx_pi_switch_to()

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Wu, Feng
> Sent: Friday, November 18, 2016 9:57 AM
> 
> PI hook vmx_pi_switch_to() is needed even when any previously

even when -> even after

> 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

which two functions?

> 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>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> v8:
> - Comments changes
> 
> 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 | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 3d330b6..f3911f2 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -222,8 +222,14 @@ 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 set 'd->arch.hvm_domain.vmx.pi_switch_to' to NULL
> +     * in vmx_pi_switch_to() if no new device 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.
> +     */

better to move this comment ahead of earlier zaps? Also seems the
comment is different from what commit msg says. Please make
them correlated.

>  }
> 
>  static int vmx_domain_initialise(struct domain *d)
> --
> 2.1.0


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