linux-kernel - Re: [PATCH 0/5] [v3] fix illegal use of _

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Date:	Tue, 26 Feb 2013 07:45:27 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Gleb Natapov <gleb@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 0/5] [v3] fix illegal use of __pa() in KVM code

On Mon, 2013-02-25 at 06:42 -0800, Dave Hansen wrote:
> On 02/24/2013 01:28 PM, Peter Hurley wrote:
> > Now that the alloc_remap() has been/is being removed, is most/all of
> > this being reverted?
> 
> I _believe_ alloc_remap() is the only case where we actually remapped
> low memory.  However, there is still other code that does __pa()
> translations for percpu areas: per_cpu_ptr_to_phys().  I _think_ it's
> still theoretically possible to get some percpu data in the vmalloc() area.
> 
> > So in short, my questions are:
> > 1) is the slow_virt_to_phys() necessary anymore?

Ah, yep. Thanks for pointing out per_cpu_ptr_to_phys().

> kvm_vcpu_arch has a
> 
>         struct pvclock_vcpu_time_info hv_clock;
> 
> and I believe I mistook the two 'hv_clock's for each other.  However,
> this doesn't hurt anything, and the performance difference is probably
> horribly tiny.

Ok. It was confusing because the fixmap of that same phys memblock done
by pvclock was broken and I couldn't understand why the hvclock memblock
needed to be looked-up per cpu. Mystery solved.

Regards,
Peter Hurley


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