Re: [PATCH] KVM: s390: vsie: retry SIE when unable to get vsie_page

[Janosch Frank <frankja@linux.ibm.com>]

On 1/16/26 16:45, Eric Farman wrote:
> On Thu, 2026-01-15 at 16:17 -0500, Eric Farman wrote:
>> On Wed, 2026-01-14 at 10:50 +0100, Claudio Imbrenda wrote:
>>> On Mon, 05 Jan 2026 10:46:53 -0500
>>> Eric Farman <farman@linux.ibm.com> wrote:
>>>
>>>> On Mon, 2026-01-05 at 13:41 +0100, Janosch Frank wrote:
>>>>> On 12/17/25 04:01, Eric Farman wrote:
>>>>>> SIE may exit because of pending host work, such as handling an interrupt,
>>>>>> in which case VSIE rewinds the guest PSW such that it is transparently
>>>>>> resumed (see Fixes tag). There is still one scenario where those conditions
>>>
>>> can you add a few words to (very briefly) explain what the scenario is?
>>
>> Maybe if this paragraph were rewritten this way, instead?
>>
>> --8<--
>> SIE may exit because of pending host work, such as handling an interrupt,
>> in which case VSIE rewinds the guest PSW such that it is transparently
>> resumed (see Fixes tag). Unlike those other places that return rc=0, this
>> return leaves the guest PSW in place, requiring the guest to handle an
>> intercept that was meant to be serviced by the host. This showed up when
>> testing heavy I/O workloads, when multiple vcpus attempted to dispatch the
>> same SIE block and incurred failures inserting them into the radix tree.
>> -->8--
> 
> Spoke to Claudio offline, and he suggested the following edit to the above:
> 
> --8<--
> SIE may exit because of pending host work, such as handling an interrupt,
> in which case VSIE rewinds the guest PSW such that it is transparently
> resumed (see Fixes tag). Unlike those other places that return rc=0, this
> return leaves the guest PSW in place, requiring the guest to handle a
> spurious intercept. This showed up when testing heavy I/O workloads,
> when multiple vcpus attempted to dispatch the same SIE block and incurred
> failures inserting them into the radix tree.
> -->8--
> 
>>
>> @Janosch, if that ends up being okay, can you update the patch or do you want me to send a v2?

I can fix that up.