linux-kernel - Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb

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Date:	Tue, 01 May 2012 15:49:50 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Avi Kivity <avi@...hat.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>, mingo@...e.hu,
	mtosatti@...hat.com, kvm@...r.kernel.org, x86@...nel.org,
	vatsa@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	hpa@...or.com, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others

On 05/01/2012 03:59 AM, Peter Zijlstra wrote:
> On Tue, 2012-05-01 at 12:57 +0200, Peter Zijlstra wrote:
>> Anyway, I don't have any idea about the costs involved with
>> HAVE_RCU_TABLE_FREE, but I don't think its much.. otherwise these other
>> platforms (PPC,SPARC) wouldn't have used it, gup_fast() is a very
>> specific case, whereas mmu-gather is something affecting pretty much all
>> tasks. 
> Which reminds me, I thought Xen needed this too, but a git grep on
> HAVE_RCU_TABLE_FREE shows its still only ppc and sparc.
>
> Jeremy?

Yeah, I was thinking that too, but I can't remember what we did to
resolve it.  For pure PV guests, gupf simply isn't used, so the problem
is moot.  But for dom0 or PCI-passthrough it could be.

Konrad, Stefano?

    J
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