Re: [Xen-devel] [PATCH 3/7] Nested VMX: Force check ISR when L2 is running

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

Jan Beulich wrote on 2013-08-09:
>>>> On 09.08.13 at 10:49, Yang Zhang <yang.z.zhang@xxxxxxxxx> wrote:
>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> 
>> If L2 is running, external interrupt is allowed to notify CPU only
>> when it has higher priority than current in servicing interrupt.
> 
> That's always this way, not just for nested HVM. Hence there must
> either be some piece missing from this explanation, or the check is
> being inserted in the wrong place.
How about change the comments like this:
External interrupt is allowed to notify CPU only when it has higher priority 
than current in servicing interrupt. With APIC-v, the priority comparing is 
done by hardware and hardware will inject the interrupt to VCPU when it 
recognizes an interrupt. Currently, there is no virtual APIC-v feature 
available for L1, so when L2 is running, we still need to compare interrupt 
priority with ISR in hypervisor instead hardware.


> Jan
> 
>> Since
>> there is no vAPIC-v for L2, so force check isr when L2 is running.
>> 
>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> ---
>>  xen/arch/x86/hvm/vlapic.c |    4 +++-
>>  1 files changed, 3 insertions(+), 1 deletions(-)
>> diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
>> index 20a36a0..f2594dd 100644
>> --- a/xen/arch/x86/hvm/vlapic.c
>> +++ b/xen/arch/x86/hvm/vlapic.c
>> @@ -37,6 +37,7 @@
>>  #include <asm/hvm/io.h> #include <asm/hvm/support.h> #include
>>  <asm/hvm/vmx/vmx.h> +#include <asm/hvm/nestedhvm.h> #include
>>  <public/hvm/ioreq.h> #include <public/hvm/params.h>
>> @@ -1037,7 +1038,8 @@ int vlapic_has_pending_irq(struct vcpu *v)
>>      if ( irr == -1 )
>>          return -1;
>> -    if ( vlapic_virtual_intr_delivery_enabled() )
>> +    if ( vlapic_virtual_intr_delivery_enabled() &&
>> +            !nestedhvm_vcpu_in_guestmode(v) )
>>          return irr;
>>      isr = vlapic_find_highest_isr(vlapic);
>> --
>> 1.7.1
> 
>


Best regards,
Yang



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