Re: [Xen-devel] [PATCH 0/4] Add posted interrupt supporting

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

On Wed, Apr 10, 2013 at 02:51:41AM +0000, Zhang, Yang Z wrote:
> Konrad Rzeszutek Wilk wrote on 2013-04-10:
> > On Tue, Apr 09, 2013 at 02:01:27PM +0800, Yang Zhang wrote:
> >> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
> >> 
> >> The follwoing patches are adding the Posted Interrupt supporting to Xen:
> >> Posted Interrupt allows vAPIC interrupts to inject into guest directly
> >> without any vmexit.
> > 
> > Is there a mechanism for the guest to figure out whether this is exported?
> Expose it to guest? No.
> 
> > 
> > Right now the Linux PVHVM guests will use the event channel mechanism
> > (via the 0xf3 callback vector). This means that if we want to do
> > IPIs (RESCHEDULE_VECTOR or CALL_FUNCTION_*) we end up doing a vmexit -
> > but with this we should be able to do these inside the guest right?
> I am not familiar with PV staffs. Will event channel mechanism touch vAPIC? 
> If no, perhaps the answer is not.

No it won't. But any any inter-OS vectors (such as IPIs) would benefit
from vAPIC right? As in posting those vectors (assuming the destination
VCPU is running) would not cause an VMEXIT?
> 
> > 
> > If so, is there a mechanism inside the guest to detect this and
> > use the HVM mechanisms for IPI?
> Why guest should aware of this? Current implementation already covers the 
> vIPI.
 
Not sure I understand you. What current implementation?

> 
> > 
> > It is mostly just the matter of not calling 'xen_hvm_smp_init' in the
> > Linux kernel.
> > 
> >> 
> >> - When delivering a interrupt to guest, if target vcpu is running,
> >>   update Posted-interrupt requests bitmap and send a notification event
> >>   to the vcpu. Then the vcpu will handle this interrupt automatically,
> >>   without any software involvemnt.
> >> - If target vcpu is not running or there already a notification event
> >>   pending in the vcpu, do nothing. The interrupt will be handled by
> >>   next vm entry
> >> Refer to Intel SDM vol3, 29.6  to get more information.
> >> 
> >> Yang Zhang (4):
> >>   VMX: Detect posted interrupt capability
> >>   VMX: Turn on posted interrupt bit in vmcs
> >>   VMX: Add posted interrupt supporting
> >>   VMX: Use posted interrupt to deliver virutal interrupt
> >>  xen/arch/x86/hvm/vioapic.c                     |    4 +-
> >>  xen/arch/x86/hvm/vlapic.c                      |   19 +++++-
> >>  xen/arch/x86/hvm/vmsi.c                        |    5 +-
> >>  xen/arch/x86/hvm/vmx/vmcs.c                    |   18 +++++-
> >>  xen/arch/x86/hvm/vmx/vmx.c                     |   81
> >>  ++++++++++++++++++++++++ xen/arch/x86/hvm/vmx/vpmu_core2.c            
> >>   |    5 +- xen/arch/x86/hvm/vpt.c                         |   10 ++-
> >>  xen/include/asm-x86/hvm/hvm.h                  |    2 +
> >>  xen/include/asm-x86/hvm/vlapic.h               |    1 +
> >>  xen/include/asm-x86/hvm/vmx/vmcs.h             |   13 ++++
> >>  xen/include/asm-x86/hvm/vmx/vmx.h              |   22 +++++++
> >>  xen/include/asm-x86/mach-default/irq_vectors.h |    3 +- 12 files
> >>  changed, 172 insertions(+), 11 deletions(-)
> >> 
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@xxxxxxxxxxxxx
> >> http://lists.xen.org/xen-devel
> >>
> 
> 
> Best regards,
> Yang
> 
> 
> 
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> 

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