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From: Paul Bolle <pebolle@tiscali.nl>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Rik van Riel <riel@redhat.com>, kvm list <kvm@vger.kernel.org>
Subject: Re: [PATCH 0/8] x86/fpu: Remove CR0.TS support
Date: Tue, 01 Nov 2016 08:51:57 +0100	[thread overview]
Message-ID: <1477986717.2230.25.camel@tiscali.nl> (raw)
In-Reply-To: <20161031234855.qu64eamohn35jdo4@pd.tnic>

On Tue, 2016-11-01 at 00:48 +0100, Borislav Petkov wrote:
> --- a/drivers/lguest/Kconfig
> +++ b/drivers/lguest/Kconfig

>  config LGUEST
>  	tristate "Linux hypervisor example code"
> -	depends on X86_32 && EVENTFD && TTY && PCI_DIRECT
> > +	depends on X86_32 && EVENTFD && TTY && PCI_DIRECT && !MICROCODE
>  	select HVC_DRIVER
>  	---help---
>  	  This is a very simple module which allows you to run

LGUEST is the symbol for host support. The symbol for guest support is
LGUEST_GUEST and it lives in arch/x86/. Yes, it's a bit of a gotcha.

> but maybe the better fix is to hack in MSR emulation in lguest and
> intercept the *MSR accesses and do the writes/reads in the exception
> fixup and ...
> 
> I haven't looked at the lguest code, of course and whether that's easily
> doable and whether it even makes sense and whether one should simply use
> qemu/kvm instead and, and, and...

Yeah, I thought about adding negative dependencies (eg, "!OLPC &&
!MICROCODE") too. But that would be contrary to the neat lguest goal to
be able to use the same kernel image as a host and a guest. At least, I
think that is one of its goals.

And as probably everybody capable of hacking on lguest (ie, other
people than me) came up with doubts similar to yours, these two issues
never got fixed.   

Thanks,


Paul Bolle

  reply	other threads:[~2016-11-01  7:52 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-31 22:18 Andy Lutomirski
2016-10-31 22:18 ` [PATCH 1/8] fpu/init: Get rid of two redundant clts() calls Andy Lutomirski
2016-11-01  7:13   ` [tip:x86/fpu] x86/fpu: " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 2/8] fpu/bugs: Stop saving and restoring CR0.TS in fpu__init_check_bugs() Andy Lutomirski
2016-11-01  7:14   ` [tip:x86/fpu] x86/fpu: " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 3/8] x86/fpu: Remove irq_ts_save() and irq_ts_restore() Andy Lutomirski
2016-11-01  7:14   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 4/8] x86/kvm: Remove host CR0.TS manipulation Andy Lutomirski
2016-11-01  7:15   ` [tip:x86/fpu] x86/fpu, kvm: " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 5/8] lguest: Remove CR0.TS support Andy Lutomirski
2016-11-01  7:15   ` [tip:x86/fpu] x86/fpu, " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 6/8] x86/fpu: #NM without FPU emulation is an error Andy Lutomirski
2016-11-01  7:16   ` [tip:x86/fpu] x86/fpu: Handle #NM without FPU emulation as " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 7/8] x86/fpu: Remove stts() Andy Lutomirski
2016-11-01  7:16   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 8/8] x86/fpu: Remove clts() Andy Lutomirski
2016-11-01  7:17   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:41 ` [PATCH 0/8] x86/fpu: Remove CR0.TS support Paul Bolle
2016-10-31 23:04   ` Borislav Petkov
2016-10-31 23:10     ` Paul Bolle
2016-10-31 23:48       ` Borislav Petkov
2016-11-01  7:51         ` Paul Bolle [this message]
2016-11-01  8:50           ` Borislav Petkov

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