Re: [Xen-devel] [PATCH v13 1/2] vmx: VT-d posted-interrupt core logic handling

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Wednesday, February 24, 2016 8:50 PM
> To: George Dunlap <george.dunlap@xxxxxxxxxx>; Wu, Feng
> <feng.wu@xxxxxxxxx>
> Cc: Doug Goldstein <cardoe@xxxxxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Dario Faggioli <dario.faggioli@xxxxxxxxxx>;
> GeorgeDunlap <george.dunlap@xxxxxxxxxxxxx>; Tian, Kevin
> <kevin.tian@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx; Keir Fraser <keir@xxxxxxx>
> Subject: Re: [Xen-devel] [PATCH v13 1/2] vmx: VT-d posted-interrupt core logic
> handling
> 
> >>> On 24.02.16 at 13:09, <george.dunlap@xxxxxxxxxx> wrote:
> > Another reason for such a comment is that it actually raises awareness
> > that the hook isn't properly structured: if you get such a compile
> > error, then it's either not defined in the right place, or it's not
> > using the right calling convention.
> 
> Well, why I generally agree with you here, I'm afraid there are
> many pre-existing instances in our headers. Cleaning that up is
> likely going to be a major work item.
> 
> > It also makes me realize that this code will no longer build on ARM,
> > since arch_do_block() is only defined in asm-x86 (and not asm-arm).
> 
> The patch has
> 
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -310,6 +310,8 @@ static inline void free_vcpu_guest_context(struct
> vcpu_guest_context *vgc)
>      xfree(vgc);
>  }
> 
> +static inline void arch_vcpu_block(struct vcpu *v) {}
> +
>  #endif /* __ASM_DOMAIN_H__ */
> 
>  /*
> 
> (and for the avoidance of doubt there's no arch_do_block() afaics).
> 
> > It seems like to do the callback properly, we should do something like
> > the attached.  Jan, what do you think?
> 
> Well, as per above that would address the particular issue here
> without addressing the many other existing ones, and it would
> cause out of line functions _plus_ another indirect call when the
> idea is to have such hooks inlined as far as possible.
> 
> But you indeed point out one important problem - the hook as it
> is right now lacks a has_hvm_container_vcpu(), and hence would
> break for PV guests.

Do you mean I need to add has_hvm_container_vcpu() check in
macro arch_vcpu_block()? But .vcpu_block is assigned in
vmx_pi_hooks_assign(). I am not clear how this hooks can affect
PV guests, could you please elaborate a bit more? Thanks a lot!

Thanks,
Feng

> 
> Jan


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