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Re: [Xen-devel] [PATCH v3 5/7] vpci: fix execution of long running operations

>>> On 08.11.18 at 14:20, <roger.pau@xxxxxxxxxx> wrote:
> On Thu, Nov 08, 2018 at 06:04:11AM -0700, Jan Beulich wrote:
>> >>> On 08.11.18 at 13:47, <roger.pau@xxxxxxxxxx> wrote:
>> > My point would be that on x86 I think the only way to have preemptible
>> > long-running operations inside of Xen is to block the guest vCPU and
>> > run them in a tasklet, or at least this seems the less invasive one.
>> > 
>> > Do you still have objections to this patch/approach?
>> Well, I still don't understand why you think you need to introduce
>> a tasklet in the first place. That's because I still don't understand
>> what you think is wrong with the current approach (leaving aside
>> the exact placement of where the vpci hook needs to be called).
> The current approach doesn't prevent the vCPU from returning to guest
> context with pending work.
> Placing the pending work hook (vpci_process_pending) in hvm_do_resume
> is not going to solve this unless we raise and process a scheduler
> softirq, and then this leads to the recursion problem.

Which recursion problem? I still haven't seen an outline taking into
account what I have written in earlier replies. In particular I don't
see a softirq handler itself calling do_softirq() anywhere.


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