From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
Jan Beulich <JBeulich@suse.com>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH] libs/guest: Don't hide the indirection on xc_cpu_policy_t
Date: Wed, 5 May 2021 11:16:08 +0200 [thread overview]
Message-ID: <YJJiWLqGoHLSnj01@Air-de-Roger> (raw)
In-Reply-To: <20210504185322.19306-1-andrew.cooper3@citrix.com>
On Tue, May 04, 2021 at 07:53:22PM +0100, Andrew Cooper wrote:
> It is bad form in C, perhaps best demonstrated by trying to read
> xc_cpu_policy_destroy(), and causes const qualification to have
> less-than-obvious behaviour (the hidden pointer becomes const, not the thing
> it points at).
Would this also affect cpuid_leaf_buffer_t and msr_entry_buffer_t
which hide an array behind a typedef?
> xc_cpu_policy_set_domain() needs to drop its (now normal) const qualification,
> as the policy object is modified by the serialisation operation.
>
> This also shows up a problem with the x86_cpu_policies_are_compatible(), where
> the intermediate pointers are non-const.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: Wei Liu <wl@xen.org>
>
> Discovered while trying to start the integration into XenServer. This wants
> fixing ASAP, before futher uses get added.
>
> Unsure what to do about x86_cpu_policies_are_compatible(). It would be nice
> to have xc_cpu_policy_is_compatible() sensibly const'd, but maybe that means
> we need a struct const_cpu_policy and that smells like it is spiralling out of
> control.
Not sure TBH, I cannot think of any alternative right now, but
introducing a const_cpu_policy feels kind of code duplication.
Thanks, Roger.
next prev parent reply other threads:[~2021-05-05 9:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-04 18:53 [PATCH] libs/guest: Don't hide the indirection on xc_cpu_policy_t Andrew Cooper
2021-05-05 6:27 ` Jan Beulich
2021-05-05 9:16 ` Roger Pau Monné [this message]
2021-05-05 12:48 ` Andrew Cooper
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