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Re: [Xen-devel] Is it safe to assume that v == current in hvm_do_resume()?

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>
  • From: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
  • Date: Wed, 22 Oct 2014 12:10:13 +0300
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  • Delivery-date: Wed, 22 Oct 2014 09:10:21 +0000
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On 10/22/2014 12:04 PM, Andrew Cooper wrote:
> On 22/10/14 09:11, Razvan Cojocaru wrote:
>> Hello,
>> As far as I've understood the code, and based on several tests, it would
>> appear that in xen/arch/x86/hvm/hvm.c, the struct vcpu *v parameter to
>> hvm_do_resume() is always equal to current.
>> Is that a reasonable assumption to make? I could have missed some use
>> cases for the function.
> The calls look like this:
> {vmx,svm}_do_resume is the schedule_tail function pointer, which is a
> no-return function and called on the way out of a context switch.
> They call hvm_do_resume() followed by a reset_stack_and_jump() to
> {vmx,svm}_asm_do_vmentry.
> So yes - you can be guaranteed that the v in hvm_do_resume() is current.
> If you do come to explicitly rely on this behaviour, and it is in any
> way unclear, it might be worth introducing an ASSERT(v == current) near
> to the expectation.

Thanks for the confirmation!

Indeed, I had placed an ASSERT() before the code that needs v == current.


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