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RE: [Xen-ia64-devel] VHPI restore mechanism at save/restore

To: "Isaku Yamahata" <yamahata@xxxxxxxxxxxxx>
Subject: RE: [Xen-ia64-devel] VHPI restore mechanism at save/restore
From: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>
Date: Fri, 1 Feb 2008 21:23:10 +0800
Cc: xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-ia64-devel] VHPI restore mechanism at save/restore
Isaku Yamahata wrote:
> On Fri, Feb 01, 2008 at 06:11:13PM +0800, Zhang, Xiantao wrote:
>> Hi,Isaku
>> I have a question about the mechanism for save/restore vhpi.  In
>> current save/restore code, vhpi register is only saved and restored
>> by vlsapic_save/load, but it maybe not enough for ensuring
>> correctness.  IMO, we need to call PAL_VPS_SET_PENDING_INTERRUPT
>> again to set it, and make cpu aware of its value.  Do I miss
>> something ? :)     
> Please notice the line in vlsapic_load()
>     v->arch.irq_new_pending = 1; /* to force checking irq */

Why need to set the force check here?   Any special reasons or scenarios which 
need it ? :)

> and see leave_hypervisor_tail() which is always called before
> entering VTi guest.
> leave_hypervisor_tail() eventually calls
> PAL_VPS_SET_PENDING_INTERRUPT. At least this is my intention. Do you
> find any path where it isn't called? 

The force check may workaround the lost VHPI, so it should work. 

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