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Re: [PATCH v2 06/16] xen/time: move ticks<->ns helpers to common code
- To: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 4 Feb 2026 09:13:28 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Romain Caritey <Romain.Caritey@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 04 Feb 2026 08:13:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 29.01.2026 09:48, Jan Beulich wrote:
> On 22.01.2026 17:47, Oleksii Kurochko wrote:
>> ticks_to_ns() and ns_to_ticks() are not architecture-specific, so provide a
>> common implementation that is more resilient to overflow than the historical
>> Arm version. This is not a practical issue for Arm, as the latest ARM ARM
>> that timer frequency should be fixed at 1 GHz and older platforms used much
>> lower rates, which is shy of 32-bit overflow. As the helpers are declared
>> as static inline, they should not affect x86, which does not use them.
>>
>> On Arm, these helpers were historically implemented as out-of-line functions
>> because the counter frequency was originally defined as static and
>> unavailable
>> to headers [1]. Later changes [2] removed this restriction, but the helpers
>> remained unchanged. Now they can be implemented as static inline without any
>> issues.
>>
>> Centralising the helpers avoids duplication and removes subtle differences
>> between architectures while keeping the implementation simple.
>>
>> Drop redundant <asm/time.h> includes where <xen/time.h> already pulls it in.
>>
>> No functional change is intended.
>>
>> [1] ddee56dc2994 arm: driver for the generic timer for ARMv7
>> [2] 096578b4e489 xen: move XEN_SYSCTL_physinfo, XEN_SYSCTL_numainfo and
>> XEN_SYSCTL_topologyinfo to common code
>>
>> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
>> Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Nit: Flip the two (chronological order).
>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Btw, if this got the necessary Arm ack, I think it could also go in ahead of
all earlier patches in the series?
Jan
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