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Message-ID: <00378f4c-ac64-459d-a990-6246a29c0ced@infradead.org>
Date: Fri, 5 Sep 2025 09:51:59 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Jiaming Zhang <r772577952@...il.com>, pbonzini@...hat.com,
seanjc@...gle.com, corbet@....net, kvm@...r.kernel.org
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Documentation: KVM: Add reference specs for PIT and LAPIC
ioctls
Hi,
On 9/5/25 12:51 AM, Jiaming Zhang wrote:
> The behavior of KVM_SET_PIT2 and KVM_SET_LAPIC conforms to their
> respective hardware specifications. Add references to the Intel 8254
> PIT datasheet and the Software Developer's Manual (SDM) to ensure
> users can rely on the official datasheets for behavioral details.
>
> Signed-off-by: Jiaming Zhang <r772577952@...il.com>
> ---
> Documentation/virt/kvm/api.rst | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 6aa40ee05a4a..d21494aa7dc2 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -2083,6 +2083,11 @@ The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's
> regs field) depends on the state of the KVM_CAP_X2APIC_API capability.
> See the note in KVM_GET_LAPIC.
>
> +.. Tip::
> + ``KVM_SET_LAPIC`` ioctl strictly adheres to IntelĀ® 64 and IA-32 Architectures
> + Software Developer's Manual (SDM). Refer volume 3A of the `Intel SDM <https://
Refer to volume 3A of the Intel SDM
> + www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html>`_.
Please put the full URL on one line -- don't split it on 2 lines.
> +
>
> 4.59 KVM_IOEVENTFD
> ------------------
> @@ -3075,6 +3080,14 @@ This IOCTL replaces the obsolete KVM_GET_PIT.
> Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2.
> See KVM_GET_PIT2 for details on struct kvm_pit_state2.
>
> +.. Tip::
> +
> + ``KVM_SET_PIT2`` ioctl strictly adheres to the spec of Intel 8254 PIT.
> + For example, a ``count`` value of 0 in ``struct kvm_pit_channel_state`` is
> + interpreted as 65536, which is the maximum count value. Refer `Intel
Refer to
> + 8254 programmable interval timer <https://www.scs.stanford.edu/10wi-cs140/
> + pintos/specs/8254.pdf>`_.
Put the full URL on one line, please.
> +
> This IOCTL replaces the obsolete KVM_SET_PIT.
>
>
Thanks.
--
~Randy
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