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Re: [Xen-devel] [PATCH] memory: don't suppress P2M update in populate_physmap()





On 06/20/2017 02:03 PM, Jan Beulich wrote:
On 20.06.17 at 14:51, <julien.grall@xxxxxxx> wrote:
On 06/20/2017 01:40 PM, Andrew Cooper wrote:
On 20/06/17 13:39, Julien Grall wrote:
On 06/20/2017 09:37 AM, Andrew Cooper wrote:
On 20/06/17 07:19, Jan Beulich wrote:
Commit d18627583d ("memory: don't hand MFN info to translated guests")
wrongly added a null-handle check there - just like stated in its
description for memory_exchange(), the array is also an input for
populate_physmap() (and hence can't reasonably be null). I have no idea
how I've managed to overlook this.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Am I correct that this is not a bug and only a pointless check?

This is a partial reversion of d18627583d and needs to be included in
4.9, to avoid a regression.

Would you mind to explain why this would introduce regression? AFAICT
the check is just redundant, so keeping it is not that bad.

Afaict there would be a regression only if someone invoked the
hypercall with a null handle (but having valid data at address zero).
Still I agree with Andrew that we'd better include this in 4.9.

Hmmm. It didn't occur to me that someone would put valid data at address zero.

Release-acked-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

--
Julien Grall

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