From: "Jan Beulich" <JBeulich@suse.com>
To: Yu Zhang <yu.c.zhang@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
xen-devel@lists.xen.org, Paul Durrant <paul.durrant@citrix.com>,
zhiyuan.lv@intel.com, Jun Nakajima <jun.nakajima@intel.com>
Subject: Re: [PATCH v5 4/4] x86/ioreq server: Reset outstanding p2m_ioreq_server entries when an ioreq server unmaps.
Date: Tue, 09 Aug 2016 02:13:06 -0600 [thread overview]
Message-ID: <57A9ACB20200007800104173@prv-mh.provo.novell.com> (raw)
In-Reply-To: <57A988C3.6010302@linux.intel.com>
>>> On 09.08.16 at 09:39, <yu.c.zhang@linux.intel.com> wrote:
>
> On 8/9/2016 12:29 AM, Jan Beulich wrote:
>>>>> On 12.07.16 at 11:02, <yu.c.zhang@linux.intel.com> wrote:
>>> @@ -5512,6 +5513,12 @@ static int hvmop_set_mem_type(
>>> if ( rc )
>>> goto out;
>>>
>>> + if ( t == p2m_ram_rw && memtype[a.hvmmem_type] == p2m_ioreq_server )
>>> + p2m->ioreq.entry_count++;
>>> +
>>> + if ( t == p2m_ioreq_server && memtype[a.hvmmem_type] == p2m_ram_rw )
>>> + p2m->ioreq.entry_count--;
>>> +
>> These (and others below) happen, afaict, outside of any lock, which
>> can't be right.
>
> How about we make this entry_count as atomic_t and use atomic_inc/dec
> instead?
That's certainly one of the options, but beware of overflow.
>>> + /*
>>> + * Iterate p2m table when an ioreq server unmaps from p2m_ioreq_server,
>>> + * and reset the remaining p2m_ioreq_server entries back to p2m_ram_rw.
>>> + */
>>> + if ( op.flags == 0 && rc == 0 )
>>> + {
>>> + struct p2m_domain *p2m = p2m_get_hostp2m(d);
>>> +
>>> + while ( gfn <= p2m->max_mapped_pfn )
>>> + {
>>> + p2m_type_t t;
>>> +
>>> + if ( p2m->ioreq.entry_count == 0 )
>>> + break;
>> Perhaps better to be moved up into the while() expression?
>
> OK. Another thing is maybe we can use _atomic_read() to get value of
> entry_count if
> the counter is defined as atomic_t?
Well, that's an orthogonal adjustment which solely depends on the
type of the field.
Jan
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next prev parent reply other threads:[~2016-08-09 8:13 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 9:02 [PATCH v5 0/4] x86/ioreq server: Introduce HVMMEM_ioreq_server mem type Yu Zhang
2016-07-12 9:02 ` [PATCH v5 1/4] x86/ioreq server: Rename p2m_mmio_write_dm to p2m_ioreq_server Yu Zhang
2016-07-12 9:02 ` [PATCH v5 2/4] x86/ioreq server: Add new functions to get/set memory types Yu Zhang
2016-07-12 9:02 ` [PATCH v5 3/4] x86/ioreq server: Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server Yu Zhang
2016-08-08 15:40 ` Jan Beulich
2016-08-09 7:39 ` Yu Zhang
2016-08-09 8:11 ` Jan Beulich
2016-08-09 8:20 ` Paul Durrant
2016-08-09 8:51 ` Yu Zhang
2016-08-09 9:07 ` Paul Durrant
2016-08-10 8:09 ` Yu Zhang
2016-08-10 10:33 ` Jan Beulich
2016-08-10 10:43 ` Paul Durrant
2016-08-10 12:32 ` Yu Zhang
2016-08-10 10:43 ` Yu Zhang
2016-08-11 8:47 ` Yu Zhang
2016-08-11 8:58 ` Jan Beulich
2016-08-11 9:19 ` Yu Zhang
2016-07-12 9:02 ` [PATCH v5 4/4] x86/ioreq server: Reset outstanding p2m_ioreq_server entries when an ioreq server unmaps Yu Zhang
2016-08-08 16:29 ` Jan Beulich
2016-08-09 7:39 ` Yu Zhang
2016-08-09 8:13 ` Jan Beulich [this message]
2016-08-09 9:25 ` Yu Zhang
2016-08-09 9:45 ` Jan Beulich
2016-08-09 10:21 ` Yu Zhang
2016-08-16 13:35 ` George Dunlap
2016-08-16 13:54 ` Jan Beulich
2016-08-30 12:17 ` Yu Zhang
2016-09-02 11:00 ` Yu Zhang
2016-08-05 2:44 ` [PATCH v5 0/4] x86/ioreq server: Introduce HVMMEM_ioreq_server mem type Yu Zhang
2016-08-05 6:16 ` Jan Beulich
2016-08-05 12:46 ` George Dunlap
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