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Re: [XEN PATCH v1] xen/arm : Add support for SMMUv3 driver
- To: Rahul Singh <Rahul.Singh@xxxxxxx>, Julien Grall <julien@xxxxxxx>
- From: Ash Wilding <Ash.Wilding@xxxxxxx>
- Date: Mon, 26 Oct 2020 12:10:51 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
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- Thread-topic: [XEN PATCH v1] xen/arm : Add support for SMMUv3 driver
Hi,
> 1. atomic_set_release
> 2. atomic_fetch_andnot_relaxed
> 3. atomic_cond_read_relaxed
> 4. atomic_long_cond_read_relaxed
> 5. atomic_long_xor
> 6. atomic_set_release
> 7. atomic_cmpxchg_relaxed might be we can use atomic_cmpxchg that is
> implemented in XEN need to check.
> 8. atomic_dec_return_release
> 9. atomic_fetch_inc_relaxed
If we're going to pull in Linux's implementations of the above atomics
helpers for SMMUv3, and given the majority of SMMUv3 systems are v8.1+
with LSE, perhaps this would be a good time to drop the current
atomic.h in Xen completely and pull in both Linux's LL/SC and LSE
helpers, then use a new Kconfig to toggle between them?
Back in 5d45ecabe3 [1] Jan mentioned we probably want to avoid relying
on gcc atomics helpers as we can't switch between LL/SC and LSE
atomics. With the above we'd be able to drop the reference to gcc's
built-in __sync_fetch_and_add() in xen/include/asm-arm/system.h by
making arch_fetch_and_add() pull in the explicit implementation of the
helper.
Thoughts?
Thanks,
Ash.
[1] https://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=5d45ecabe3
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