Re: [Xen-devel] RE: [Xen-changelog] [xen-unstable]vt-d: Fixpanic in msi_msg_read_remap_rte with acpi=off

[Miroslav Rezanina <mrezanin@xxxxxxxxxx>]

----- "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> From: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
> To: "Miroslav Rezanina" <mrezanin@xxxxxxxxxx>, "Dexuan Cui" 
> <dexuan.cui@xxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Sent: Monday, October 19, 2009 11:22:48 AM GMT +01:00 Amsterdam / Berlin / 
> Bern / Rome / Stockholm / Vienna
> Subject: Re: [Xen-devel] RE: [Xen-changelog] [xen-unstable]vt-d: Fixpanic in 
> msi_msg_read_remap_rte with acpi=off
>
> On 19/10/2009 09:34, "Miroslav Rezanina" <mrezanin@xxxxxxxxxx> wrote:
> 
> >> Thanks,
> >> -- Dexuan
> >> 
> > 
> > Hi Dexuan,
> > you're right. We should print warning. In your patch, I do not
> understand
> > why you put comment only in setup_dom0_devices function. There is
> more
> > calling of domain_context_mapping and we check NULL also in
> > domain_context_unmap
> > and reassign_device_ownership. We should put warning in there too,
> shouldn't
> > we?
> 
> The warnings are silly, if we believe find_matched_drhd_unit() should
> not
> return NULL in those cases. Since obviously we wouldn't know what to
> do in
> that case: bailing and doing nothing, while convenient and requiring
> little
> thought to implement, probably causes other subtler problems later on
> since
> those remap functions are supposed to actually do something! Crashing
> immediately is the nice thing to do here: nice for the poor developer
> who
> may have to debug this case sometime in the future, in the hopefully
> unlikely event our belief turns out to be false.
> 
> I'll be applying Dexuan's original replacement patch.
> 
>  -- Keir
> 

I retest version with removed NULL checks and in this case, my system crashes.
So there has to be checks for NULL or something else is wrong.

Regards,
Mirek

> 
> 
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-- 
Miroslav Rezanina
Software Engineer - Virtualization Team - XEN kernel


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