Re: [Xen-devel] [PATCH for-xen-4.5] libxl: Allow copying smaller bitmap into a larger one

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Nov 25, 2014 at 09:57:54AM -0500, Boris Ostrovsky wrote:
> On 11/25/2014 06:41 AM, Dario Faggioli wrote:
> >On Tue, 2014-11-25 at 11:15 +0000, Wei Liu wrote:
> >>And here it is.
> >>
> >>Boris, can you give it a shot?
> >>
> >>---8<---
> >> From 77531e31d239887b9f36c03e434300bc30683092 Mon Sep 17 00:00:00 2001
> >>From: Wei Liu <wei.liu2@xxxxxxxxxx>
> >>Date: Tue, 25 Nov 2014 10:59:47 +0000
> >>Subject: [PATCH] libxl: allow copying between bitmaps of different sizes
> >>
> >>When parsing bitmap objects JSON parser will create libxl_bitmap map of the
> >>smallest size needed.
> >>
> >>This can cause problems when saved image file specifies CPU affinity.  For
> >>example, if 'vcpu_hard_affinity' in the saved image has only the first CPU
> >>specified, just a single byte will be allocated and libxl_bitmap->size will 
> >>be
> >>set to 1.
> >>
> >>This will result in assertion in 
> >>libxl_set_vcpuaffinity()->libxl_bitmap_copy()
> >>since the destination bitmap is created for maximum number of CPUs.
> >>
> >>We could allocate that bitmap of the same size as the source, however, it is
> >>later passed to xc_vcpu_setaffinity() which expects it to be sized to the 
> >>max
> >>number of CPUs
> >>
> >>To fix this issue, introduce an internal function to allowing copying 
> >>between
> >>bitmaps of different sizes. Note that this function is only used in
> >>libxl_set_vcpuaffinity at the moment. Though NUMA placement logic invoke
> >>libxl_bitmap_copy as well there's no need to replace those invocations.  
> >>NUMA
> >>placement logic comes into effect when no vcpu / node pinning is provided, 
> >>so
> >>it always operates on bitmap of the same sizes (that is, size of maximum
> >>number of cpus /nodes).
> >>
> >>Reported-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> >>Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> >>Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >>Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> >>Cc: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> >>
> >If this end up being the approach, it can have the following:
> >
> >Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> 
> Tested-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

Thank you!
> 
> 

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