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From: Sergey Fedorov <serge.fdrv@gmail.com>
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Date: Wed, 11 May 2016 16:42:10 +0300
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Subject: Re: [Qemu-devel] [RFC v2 05/11] tcg: protect TBContext with tb_lock.
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To: Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, mttcg@greensocs.com, fred.konrad@greensocs.com, a.rigo@virtualopensystems.com, cota@braap.org
Cc: qemu-devel@nongnu.org, mark.burton@greensocs.com, jan.kiszka@siemens.com, rth@twiddle.net, peter.maydell@linaro.org, claudio.fontana@huawei.com, Peter Crosthwaite <crosthwaite.peter@gmail.com>, "Michael S. Tsirkin" <mst@redhat.com>, Eduardo Habkost <ehabkost@redhat.com>

On 11/05/16 15:52, Paolo Bonzini wrote:
> Just a couple answers/remarks.
>
> On 11/05/2016 14:45, Sergey Fedorov wrote:
(snip)
>>> @@ -1350,6 +1352,7 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
>>>      /* we remove all the TBs in the range [start, end[ */
>>>      /* XXX: see if in some cases it could be faster to invalidate all
>>>         the code */
>>> +    tb_lock();
>> Don't we need also protect a call to page_find() above? page_find()
>> calls page_find_alloc() which is noted to be called with 'tb_lock' held.
> Only if alloc=1; page_find calls it with alloc=0.

Year, right :)

>> However, it might depend on the way we treat 'mmap_lock' in system mode
>> emulation.
> It's just not there; generally speaking it's replaced with tb_lock.

So why do we need yet another lock, 'mmap_lock', for user-mode emulation
and don't need it for system mode?

Kind regards,
Sergey