From: Nuno Das Neves <[email protected]> Sent: Friday, October 17, 2025 11:58 AM > > When the MSHV_ROOT_HVCALL ioctl is executing a hypercall, and gets > HV_STATUS_INSUFFICIENT_MEMORY, it deposits memory and then returns > -EAGAIN to userspace. The expectation is that the VMM will retry. > > However, some VMM code in the wild doesn't do this and simply fails. > Rather than force the VMM to retry, change the ioctl to deposit > memory on demand and immediately retry the hypercall as is done with > all the other hypercall helper functions. > > In addition to making the ioctl easier to use, removing the need for > multiple syscalls improves performance. > > There is a complication: unlike the other hypercall helper functions, > in MSHV_ROOT_HVCALL the input is opaque to the kernel. This is > problematic for rep hypercalls, because the next part of the input > list can't be copied on each loop after depositing pages (this was > the original reason for returning -EAGAIN in this case). > > Introduce hv_do_rep_hypercall_ex(), which adds a 'rep_start' > parameter. This solves the issue, allowing the deposit loop in > MSHV_ROOT_HVCALL to restart a rep hypercall after depositing pages > partway through. > > Signed-off-by: Nuno Das Neves <[email protected]>
Reviewed-by: Michael Kelley <[email protected]> > --- > > Changes in v2: > - Improve commit message [Michael] > - Fix up some incorrect/incomplete comments [Michael] > > --- > drivers/hv/mshv_root_main.c | 58 ++++++++++++++++++---------------- > include/asm-generic/mshyperv.h | 17 ++++++++-- > 2 files changed, 44 insertions(+), 31 deletions(-) >
