Re: [Xen-devel] [for-4.7] x86/emulate: synchronize LOCKed instruction emulation

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> 04/14/16 10:50 AM >>>
>On 04/14/2016 07:35 AM, Jan Beulich wrote:
>>> --- a/xen/arch/x86/hvm/emulate.c
>>> >+++ b/xen/arch/x86/hvm/emulate.c
>>> >@@ -25,6 +25,8 @@
>>  >#include <asm/hvm/svm/svm.h>
>>  >#include <asm/vm_event.h>
>>  >
>>> >+DEFINE_PERCPU_RWLOCK_GLOBAL(emulate_locked_rwlock);
>> You should try hard to make this static.
>
>On second though, this would make the code somewhat more convoluted, as
>the functions in emulate.c need to access this variable, and so does the
>code in domain.c that initializes the lock when the domain is created.
>
>What I've done is similar to what I found in the current source code with:
>
>arch/x86/mm/p2m.c:DEFINE_PERCPU_RWLOCK_GLOBAL(p2m_percpu_rwlock);
>common/grant_table.c:DEFINE_PERCPU_RWLOCK_GLOBAL(grant_rwlock);

Well, that's why I said "you should try hard" instead of "you have to".

>But I could add a function to emulate.h, for example:
>
>void init_emulate_smp_lock();

Exactly (just that this is perhaps again the wrong header, considering you
also need this for PV emulation).

>and call that from arch/x86/domain.c (as suggested by Andrew Cooper),
>which would allow domain.c to stop referencing emulate_locked_rwlock
>directly.

Right, and to be honest I can't really see how my earlier comment could
have been taken for "add an ARM stub".

Jan


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