From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH] x86: svm: make wbinvd faster
Date: Tue, 10 Mar 2015 12:01:31 +0100
Message-ID: <20150310110131.GA12854@potion.brq.redhat.com>
References: <20150228001917.15247.41063.stgit@joelvmguard2.amd.com>
 <20150309232846.GB12125@amt.cnet>
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Cc: Joel Schopp <joel.schopp@amd.com>, Gleb Natapov <gleb@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
	David Kaplan <David.Kaplan@amd.com>,
	Joerg Roedel <joro@8bytes.org>, linux-kernel@vger.kernel.org,
	Borislav Petkov <bp@alien8.de>
To: Marcelo Tosatti <mtosatti@redhat.com>
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2015-03-09 20:28-0300, Marcelo Tosatti:
> On Fri, Feb 27, 2015 at 06:19:18PM -0600, Joel Schopp wrote:
> > From: David Kaplan <David.Kaplan@amd.com>
> > No need to re-decode WBINVD since we know what it is from the intercept.
> > 
> > Signed-off-by: David Kaplan <David.Kaplan@amd.com>
> > [extracted from larger unlrelated patch, forward ported, tested]
> > Signed-off-by: Joel Schopp <joel.schopp@amd.com>
> 
> Can't you disable the intercept if need_emulate_wbinvd(vcpu) == false? 

I don't think we want to:  it should be faster to intercept and ignore
than to invalidate all caches.  The exit doesn't affect other physical
cores and costs just about 10(?) L3 cache misses.