From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>,
Jan Beulich <JBeulich@suse.com>,
Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH 2/4] tools/libxc: Use an explicit check for PV MSRs in xc_domain_save()
Date: Fri, 6 Jun 2014 10:44:53 +0100 [thread overview]
Message-ID: <53918D95.4080504@citrix.com> (raw)
In-Reply-To: <1402046150.31120.0.camel@kazak.uk.xensource.com>
On 06/06/14 10:15, Ian Campbell wrote:
> On Thu, 2014-06-05 at 16:57 +0100, Andrew Cooper wrote:
>> To avoid a race condition with the vcpu touching a new MSR between the
>> two hypercalls, Xen must return the maximum possible msr_count with the
>> request for size, so the toolstack can guarantee to allocate a large
>> enough buffer.
> If the msr_count returned a build time constant can't it just be part of
> the interface then? Either as #define or an explicitly sized array type
> somewhere.
>
> Ian.
>
The maximum possible msr_count depends on architecture, features
available and, plausibly, domain cpuid policy.
At the moment it is trivial, Intel = 0 and AMD = {0, 4}, but this will
get more complicated as we add support for more MSRs.
The information does have to be made available on a per-domain basis.
~Andrew
next prev parent reply other threads:[~2014-06-06 9:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-04 17:26 [PATCH 0/4] Fixes to several domctls for migration Andrew Cooper
2014-06-04 17:26 ` [PATCH 1/4] x86/domctl: Implement XEN_DOMCTL_{get, set}_vcpu_msrs Andrew Cooper
2014-06-05 12:46 ` Jan Beulich
2014-06-05 13:01 ` Andrew Cooper
2014-06-05 13:33 ` Jan Beulich
2014-06-06 14:53 ` Andrew Cooper
2014-06-06 15:09 ` Jan Beulich
2014-06-06 15:28 ` Andrew Cooper
2014-06-04 17:26 ` [PATCH 2/4] tools/libxc: Use an explicit check for PV MSRs in xc_domain_save() Andrew Cooper
2014-06-05 13:41 ` Jan Beulich
2014-06-05 15:52 ` Ian Campbell
2014-06-05 15:57 ` Andrew Cooper
2014-06-06 9:15 ` Ian Campbell
2014-06-06 9:44 ` Andrew Cooper [this message]
2014-06-06 9:48 ` Ian Campbell
2014-06-04 17:26 ` [PATCH 3/4] x86/domctl: Remove PV MSR parts of XEN_DOMCTL_[gs]et_ext_vcpucontext Andrew Cooper
2014-06-05 7:52 ` Frediano Ziglio
2014-06-05 9:25 ` Andrew Cooper
2014-06-04 17:26 ` [PATCH 4/4] x86/domctl: Two functional fixes to XEN_DOMCTL_[gs]etvcpuextstate Andrew Cooper
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