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From: Tyler Hicks <tyhicks@canonical.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v8 3/5] NX 3
Date: Fri, 1 Nov 2019 13:51:27 -0500	[thread overview]
Message-ID: <20191101185126.GA12673@elm> (raw)
In-Reply-To: <20191101183815.GA6582@u1904>

On 2019-11-01 11:38:15, speck for mark gross wrote:
> On Fri, Nov 01, 2019 at 08:07:27AM +0100, speck for Paolo Bonzini wrote:
> > On 01/11/19 01:24, speck for Pawan Gupta wrote:
> > > On Fri, Nov 01, 2019 at 12:33:45AM +0100, speck for Paolo Bonzini wrote:
> > >> From: Paolo Bonzini <pbonzini@redhat.com>
> > >> Subject: [PATCH v8 3/5] kvm: mmu: ITLB_MULTIHIT mitigation
> > >>  
> > >> +	kvm.nx_huge_pages=
> > >> +			[KVM] Controls the sw workaround for bug
> > >> +			X86_BUG_ITLB_MULTIHIT.
> > >> +			force	: Always deploy workaround.
> > >> +			off	: Default. Never deploy workaround.
> > > 
> > > off is not the default in the code, so the default should be "auto" here.
> > > 
> > >> +			auto	: Deploy workaround based on presence of
> > >> +				  X86_BUG_ITLB_MULTIHIT.
> > > 
> > > Also mitigations=off is not disabling this mitigation. Below patch does
> > > that when mitigations=off and kvm.nx_huge_pages=auto.
> > > 
> > > ---
> > > From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
> > > Date: Wed, 30 Oct 2019 21:28:24 -0700
> > > Subject: [PATCH] kvm: x86: mmu: Apply global mitigations knob to ITLB_MULTIHIT
> > > 
> > > Problem: The global mitigation knob mitigations=off does not turn off
> > > X86_BUG_ITLB_MULTIHIT mitigation.
> > > 
> > > Fix: Turn off the mitigation when ITLB_MULTIHIT mitigation mode is
> > > "auto" and mitigations are turned off globally via cmdline
> > > mitigations=off.
> > > 
> > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
> > 
> > Thanks, I'll post v9 soon.  Are you going to post backports as bundles
> > on top of Thomas's?
> > 
> > Paolo
> We (I) have attempted the backports of this and quicly hit issues with the page
> zapping changes do to code flux in the upstream.  My troubles started with with
> 5.2 and 4.19. 

Is this due to the lack of kvm_mmu_zap_all_fast()? I believe that Paolo
and others said in an older thread that
kvm_mmu_invalidate_zap_all_pages() could be used instead.

That's what I've been planning to do in Ubuntu but I haven't had a
chance to test it yet.

Tyler

> I have reached out to an internal resource who is more knowledgable
> with KVM mm files to assist with that aspect of the backport.  The
> engineer was at a confrence this week and we hope to make more
> progress next week once he is back.
> 
> --mark
> 

  reply	other threads:[~2019-11-01 18:51 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-31 23:33 [MODERATED] [PATCH v8 0/5] NX 0 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 1/5] NX 1 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 2/5] NX 2 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 3/5] NX 3 Paolo Bonzini
2019-11-01  0:24   ` [MODERATED] " Pawan Gupta
2019-11-01  7:07     ` Paolo Bonzini
2019-11-01 18:38       ` mark gross
2019-11-01 18:51         ` Tyler Hicks [this message]
2019-11-01 20:36           ` mark gross
2019-11-02  7:36             ` Paolo Bonzini
2019-11-01 14:58     ` Tyler Hicks
2019-11-01 15:43       ` [MODERATED] [PATCH] NX build fixup Tyler Hicks
2019-11-01 16:31         ` [MODERATED] " Josh Poimboeuf
2019-11-01 20:39           ` [MODERATED] [PATCH v2] " Tyler Hicks
2019-11-01 21:14             ` [MODERATED] " Josh Poimboeuf
2019-11-01 21:38             ` [MODERATED] Re: [PATCH v2] NX mitigations=off fix Pawan Gupta
2019-10-31 23:33 ` [MODERATED] [PATCH v8 4/5] NX 4 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 5/5] NX 5 Paolo Bonzini

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