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Re: [PATCH v2 06/39] xen/riscv: use UINT64_MAX to disable the VS-timer
- To: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- From: Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>
- Date: Mon, 31 Aug 2026 14:48:15 +0200
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Romain Caritey <Romain.Caritey@xxxxxxxxxxxxx>, Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>, Zheng Zhang <zhangzheng@xxxxxxxxxxx>, Alistair Francis <alistair.francis@xxxxxxx>, Connor Davis <connojdavis@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger@xxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Mon, 31 Aug 2026 12:48:48 +0000
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On Thu, 27 Aug 2026 17:20:50 +0200, Oleksii Kurochko
<oleksii.kurochko@xxxxxxxxx> wrote:
> vstimecmp is a 64-bit CSR independently of XLEN, which is why it is
> written with csr_write64(). On RV32 that macro splits the value into
> the vstimecmp/vstimecmph pair, so passing ULONG_MAX (0xffffffff there)
> writes all ones to the low half and zero to the high half, leaving the
> CSR at 0x00000000ffffffff rather than at its maximum. A VS-timer irq
> would then become pending as soon as (time + htimedelta) reaches 2^32,
> which is exactly what the code is trying to avoid.
>
> [...]
Reviewed-by: Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>
--
Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>
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