RE: [v3 23/26] KVM: Update Posted-Interrupts Descriptor when vCPU is preempted

[Wu, Feng]

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx
> [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Paolo Bonzini
> Sent: Thursday, December 18, 2014 4:32 PM
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx
> Subject: Re: [v3 23/26] KVM: Update Posted-Interrupts Descriptor when vCPU
> is preempted
> 
> 
> 
> On 18/12/2014 04:15, Wu, Feng wrote:
> > Thanks for your comments, Paolo!
> >
> > If we use u64 new_control, we cannot use new.sn any more.
> > Maybe we can change the struct pi_desc {} like this:
> >
> > typedef struct pid_control{
> >         u64     on      : 1,
> >         sn      : 1,
> >         rsvd_1  : 13,
> >         ndm     : 1,
> >         nv      : 8,
> >         rsvd_2  : 8,
> >         ndst    : 32;
> > }pid_control_t;
> >
> > struct pi_desc {
> >         u32 pir[8];     /* Posted interrupt requested */
> > 		pid_control_t control;
> 
> Probably something like this to keep the union:
> 
> typedef union pid_control {
> 	u64 full;
> 	struct {
> 		u64 on : 1,
> 		...
> 	} fields;
> };
> 
> >         u32 rsvd[6];
> > } __aligned(64);
> >
> >
> > Then we can define pid_control_t new_control, old_control. And use
> new_control.sn = 0.
> >
> > What is your opinon?
> 
> Sure.  Alternatively, keep using struct pi_desc new; just
> do not zero it, nor access any field outide the control word.
> 
> Paolo

Yes, this is also a good idea. Thanks!

Thanks,
Feng

> 
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