Re: [PATCH v2 3/3] KVM: s390: Use generic VIRT_XFER_TO_GUEST_WORK functions

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

On 11/26/25 06:33, Andrew Donnellan wrote:
> Switch to using the generic infrastructure to check for and handle pending
> work before transitioning into guest mode.
> 
> xfer_to_guest_mode_handle_work() does a few more things than the current
> code does when deciding whether or not to exit the __vcpu_run() loop. The
> exittime tests from kvm-unit-tests, in my tests, were within a few percent
> compared to before this series, which is within noise tolerance.
> 
> Co-developed-by: Heiko Carstens <hca@linux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> ---
> v2: if work is handled, recheck for outstanding work with interrupts
>      disabled before entering guest (Heiko)
> 
> The way I've implemented this, I do the check between vcpu_pre_run() and
> entering the guest, and bail out of the loop if
> kvm_xfer_to_guest_mode_handle_work() returns nonzero, without calling
> vcpu_post_run(). My impression is that this is safe, but it does mean
> there is an sie_enter vcpu event and trace event which isn't matched with
> corresponding exit events. Is this a problem?


Acked-by: Janosch Frank <frankja@linux.ibm.com>