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Re: [PATCH v4 1/3] time: add "NOW() good" indicator
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Tue, 18 Aug 2026 17:10:46 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- Delivery-date: Tue, 18 Aug 2026 15:11:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 30-Jun-26 16:06, Jan Beulich wrote:
> printk_start_of_line() checks for a value of 0 right now. In order to be
> able to have NOW() return at least monotonically increasing values, that
> needs replacing by an explicit indicator.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
> ---
> Arm and RISC-V may want to consider whether their initial get_cycles()
> can't be moved yet earlier, such that the indicator also can be set
> yet earlier.
On Arm, get_cycles() just reads a system register and it could be moved earlier.
That said, is there any rule as to what should actually be considered a start of
time (i.e. the boot_count value)? At the moment, this denotes the moment where
the time driver is set up in preinit_xen_time() after validating the frequency.
~Michal
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