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

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Konrad Rzeszutek Wilk wrote on 2013-04-10:
> 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?
Yes.

>> 
>>> 
>>> 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?
I thought you mean the vIPI. Obviously, I am wrong. :(
What does " HVM mechanisms for IPI " mean? 

> 
>> 
>>> 
>>> 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
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>>


Best regards,
Yang


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