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From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arch@vger.kernel.org, "Juergen Gross" <jgross@suse.com>,
	"Jeremy Fitzhardinge" <jeremy@goop.org>,
	x86@kernel.org, kvm@vger.kernel.org,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Pan Xinhui" <xinhui.pan@linux.vnet.ibm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Rusty Russell" <rusty@rustcorp.com.au>,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	"Chris Wright" <chrisw@sous-sol.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	andrew.cooper3@citrix.com, "H. Peter Anvin" <hpa@zytor.com>,
	xen-devel@lists.xenproject.org,
	"Alok Kataria" <akataria@vmware.com>,
	"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64
Date: Thu, 16 Feb 2017 16:00:10 -0500	[thread overview]
Message-ID: <9c101df4-7320-556a-ca41-e024629e9a67__441.110510337417$1487278899$gmane$org@redhat.com> (raw)
In-Reply-To: <20170216164815.GD6515@twins.programming.kicks-ass.net>

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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      parent reply	other threads:[~2017-02-16 21:00 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-15 21:37 [PATCH v4 0/2] x86/kvm: Reduce vcpu_is_preempted() overhead Waiman Long
2017-02-15 21:37 ` [PATCH v4 1/2] x86/paravirt: Change vcp_is_preempted() arg type to long Waiman Long
2017-02-15 21:37 ` Waiman Long
2017-02-15 21:37 ` Waiman Long
2017-02-16 16:09   ` Peter Zijlstra
2017-02-16 16:09   ` Peter Zijlstra
2017-02-16 16:09     ` Peter Zijlstra
2017-02-16 21:02     ` Waiman Long
2017-02-16 21:02     ` Waiman Long
2017-02-16 21:02       ` Waiman Long
2017-02-17  9:42       ` Peter Zijlstra
2017-02-17  9:42         ` Peter Zijlstra
2017-02-17  9:42       ` Peter Zijlstra
2017-02-15 21:37 ` [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64 Waiman Long
2017-02-15 21:37 ` Waiman Long
2017-02-15 21:37   ` Waiman Long
2017-02-16 16:48   ` Peter Zijlstra
2017-02-16 16:48   ` Peter Zijlstra
2017-02-16 16:48     ` Peter Zijlstra
2017-02-16 21:00     ` Waiman Long
2017-02-16 21:00       ` Waiman Long
2017-02-16 21:00     ` Waiman Long [this message]

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