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Re: [PATCH v2] x86/flushtlb: remove flush_area check on system state
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 25 May 2022 09:34:32 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 25 May 2022 07:34:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.05.2022 09:21, Roger Pau Monné wrote:
> On Wed, May 25, 2022 at 08:02:17AM +0200, Jan Beulich wrote:
>> On 24.05.2022 18:46, Roger Pau Monné wrote:
>>> Would you be fine with adding:
>>>
>>> Note that FLUSH_FORCE_IPI doesn't need to be handled explicitly, as
>>> it's main purpose is to prevent the usage of the hypervisor assisted
>>> flush if available, not to force the sending of an IPI even for cases
>>> where it won't be sent.
>>
>> Hmm, yes, that's even more verbose than I would have expected it to
>> be. Just one point: I'm not sure about "main" there. Is there really
>> another purpose?
>
> Right, I should remove main.
>
>> Of course an alternative would be to rename the flag to properly
>> express what it's for (e.g. FLUSH_NO_HV_ASSIST). This would then
>> eliminate the need for a comment, afaic at least.
>
> I think it's likely that we also require this flag if we make use of
> hardware assisted flushes in the future, and hence it would better
> stay with the current name to avoid renaming in the future.
>
> Whether the avoidance of sending the IPI is due to hardware or
> hypervisor assistance is of no interest to the caller, it only cares
> to force a real IPI to be sent to remote processors.
Well, then it could still be named FLUSH_NO_ASSIST, since as said
(and as you look to agree with) there's no IPI being forced in the
general case.
Jan
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