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Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64

From Waiman Long <longman@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64
Date 2017-02-16 22:10 +0100
Message-ID <tbBtn-3uQ-5@gated-at.bofh.it> (permalink)
References <tbfsS-5g5-1@gated-at.bofh.it> <tbfsS-5g5-7@gated-at.bofh.it> <tbxpM-zM-31@gated-at.bofh.it>
Organization Red Hat

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On 02/16/2017 11:48 AM, Peter Zijlstra wrote:
> On Wed, Feb 15, 2017 at 04:37:50PM -0500, Waiman Long wrote:
>> +/*
>> + * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
>> + * restoring to/from the stack. It is assumed that the preempted value
>> + * is at an offset of 16 from the beginning of the kvm_steal_time structure
>> + * which is verified by the BUILD_BUG_ON() macro below.
>> + */
>> +#define PREEMPTED_OFFSET	16
> As per Andrew's suggestion, the 'right' way is something like so.

Thanks for the tip. I was not aware of the asm-offsets stuff. I will
update the patch to use it.

Cheers,
Longman

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[PATCH v4 0/2] x86/kvm: Reduce vcpu_is_preempted() overhead  Waiman Long <longman@redhat.com> - 2017-02-15 22:40 +0100
  [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64 Waiman Long <longman@redhat.com> - 2017-02-15 22:40 +0100
    Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of  vcpu_is_preempted() for x86-64 Peter Zijlstra <peterz@infradead.org> - 2017-02-16 17:50 +0100
      Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of  vcpu_is_preempted() for x86-64 Waiman Long <longman@redhat.com> - 2017-02-16 22:10 +0100
  [PATCH v4 1/2] x86/paravirt: Change vcp_is_preempted() arg type to long Waiman Long <longman@redhat.com> - 2017-02-15 22:40 +0100
    Re: [PATCH v4 1/2] x86/paravirt: Change vcp_is_preempted() arg type  to long Peter Zijlstra <peterz@infradead.org> - 2017-02-16 17:20 +0100
      Re: [PATCH v4 1/2] x86/paravirt: Change vcp_is_preempted() arg type  to long Waiman Long <longman@redhat.com> - 2017-02-16 22:10 +0100
        Re: [PATCH v4 1/2] x86/paravirt: Change vcp_is_preempted() arg type  to long Peter Zijlstra <peterz@infradead.org> - 2017-02-17 10:50 +0100

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