From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Jeremy Fitzhardinge" <jeremy@goop.org>,
"Chris Wright" <chrisw@sous-sol.org>,
"Alok Kataria" <akataria@vmware.com>,
"Rusty Russell" <rusty@rustcorp.com.au>,
"Ingo Molnar" <mingo@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
xen-devel@lists.xenproject.org, kvm@vger.kernel.org,
"Pan Xinhui" <xinhui.pan@linux.vnet.ibm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Juergen Gross" <jgross@suse.com>,
andrew.cooper3@citrix.com
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@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
prev parent reply other threads:[~2017-02-16 21:00 UTC|newest]
Thread overview: 8+ 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
2017-02-16 16:09 ` Peter Zijlstra
2017-02-16 21:02 ` Waiman Long
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
2017-02-16 16:48 ` Peter Zijlstra
2017-02-16 21:00 ` Waiman Long [this message]
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