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Re: [PATCH v2 2/3] x86/viridian: Implement synthetic timer direct mode
- To: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 7 Sep 2026 11:02:44 +0200
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- Cc: Paul Durrant <paul@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger@xxxxxxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 07 Sep 2026 09:02:51 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.09.2026 16:15, Ross Lagerwall wrote:
> @@ -368,11 +379,18 @@ int viridian_time_wrmsr(struct vcpu *v, uint32_t idx,
> uint64_t val)
> if ( !(viridian_feature_mask(d) & HVMPV_stimer) )
> return X86EMUL_EXCEPTION;
>
> + new.as_uint64 = val;
> + if ( new.direct_mode &&
> + !(viridian_feature_mask(d) & HVMPV_stimer_direct) )
> + return X86EMUL_EXCEPTION;
> +
> stop_stimer(vs);
>
> vs->config.as_uint64 = val;
>
> - if ( !vs->config.sintx || !vs->count )
> + if ( (vs->config.direct_mode &&
> + (vs->config.sintx || vs->config.apic_vector < 0x10)) ||
> + (!vs->config.direct_mode && !vs->config.sintx) || !vs->count )
> vs->config.enable = 0;
Personally I find conditionals like this one ((a && ...) || (!a && ...))
pretty odd to read. Imo that's a case where the conditional operator is
quite helpful:
if ( (vs->config.direct_mode
? vs->config.sintx || vs->config.apic_vector < 0x10
: !vs->config.sintx) ||
!vs->count )
(Of course further adjustments are going to be needed here to address
Roger's comment.)
Jan
|
