From: Julien Grall <julien@xen.org>
To: Paul Durrant <pdurrant@amazon.com>, xen-devel@lists.xenproject.org
Cc: "Kevin Tian" <kevin.tian@intel.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Jun Nakajima" <jun.nakajima@intel.com>, "Wei Liu" <wl@xen.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"George Dunlap" <George.Dunlap@eu.citrix.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 3/3] x86 / vmx: use a 'normal' domheap page for APIC_DEFAULT_PHYS_BASE
Date: Tue, 21 Jan 2020 12:29:03 +0000 [thread overview]
Message-ID: <1c6f1cc1-d341-791e-bdc1-4f2d6beb2495@xen.org> (raw)
In-Reply-To: <20200121120009.1767-4-pdurrant@amazon.com>
Hi,
On 21/01/2020 12:00, Paul Durrant wrote:
> diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
> index 919a270587..ef327072ed 100644
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -2269,7 +2269,8 @@ int assign_pages(
>
> if ( !(memflags & MEMF_no_refcount) )
> {
> - if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) )
> + if ( unlikely((d->tot_pages + (1 << order)) > d->max_pages) &&
> + d->creation_finished )
This is not entirely obvious to me how this is safe. What would happen
if d->creation_finished is set on another CPU at the same time? At least
on Arm, this may not be seen directly.
I guess the problem would not only happen in this use case (I am more
concerned in the physmap code), but it would be good to document how it
is meant to be safe to use.
However, AFAIU, the only reason for the check to be here is because
d->max_pages is set quite late. How about setting max_pages as part of
the domain_create hypercall?
Cheers,
--
Julien Grall
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next prev parent reply other threads:[~2020-01-21 12:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 12:00 [Xen-devel] [PATCH 0/3] purge free_shared_domheap_page() Paul Durrant
2020-01-21 12:00 ` [Xen-devel] [PATCH 1/3] x86 / vmx: make apic_access_mfn type-safe Paul Durrant
2020-01-22 2:51 ` Tian, Kevin
2020-01-22 14:05 ` Andrew Cooper
2020-01-22 15:48 ` Jan Beulich
2020-01-21 12:00 ` [Xen-devel] [PATCH 2/3] x86 / hvm: add domain_relinquish_resources() method Paul Durrant
2020-01-22 15:50 ` Jan Beulich
2020-01-22 15:56 ` Durrant, Paul
2020-01-22 16:00 ` Jan Beulich
2020-01-22 16:02 ` Durrant, Paul
2020-01-21 12:00 ` [Xen-devel] [PATCH 3/3] x86 / vmx: use a 'normal' domheap page for APIC_DEFAULT_PHYS_BASE Paul Durrant
2020-01-21 12:29 ` Julien Grall [this message]
2020-01-21 12:37 ` Durrant, Paul
2020-01-22 3:19 ` Tian, Kevin
2020-01-22 11:25 ` Durrant, Paul
2020-01-22 16:17 ` Jan Beulich
2020-01-22 16:27 ` Durrant, Paul
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