On Tue, Sep 15, 2026 at 10:11:36AM +0530, Naman Jain wrote:
>
>
> On 9/11/2026 11:21 PM, Hardik Garg wrote:
> > Register-page setup is optional for each CPU. If allocation or
> > registration fails, mshv_vtl_configure_reg_page() warns and leaves that
> > CPU's reg_page NULL, but initial context setup continues successfully.
> > Meanwhile, successful setup on another CPU sets the global
> > mshv_has_reg_page flag.
> >
> > mshv_vtl_fault() checks this global flag before selecting the requested
> > CPU's register page. With mixed setup results across online CPUs, the
> > check passes even for a CPU with no register page, reaching
> > get_page(NULL) when userspace faults in that mapping.
> >
> > Check the selected per-CPU register page before taking its reference and
> > return VM_FAULT_SIGBUS if it is absent.
> >
> > Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver")
> > Cc: [email protected]
> > Signed-off-by: Hardik Garg <[email protected]>
> > ---
> > drivers/hv/mshv_vtl_main.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c
> > index fc993560a45c..3296ab5c0243 100644
> > --- a/drivers/hv/mshv_vtl_main.c
> > +++ b/drivers/hv/mshv_vtl_main.c
> > @@ -912,6 +912,9 @@ static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf)
> > return VM_FAULT_NOPAGE;
> > }
> > + if (!page)
> > + return VM_FAULT_SIGBUS;
> > +
> > get_page(page);
> > vmf->page = page;
>
>
> LGTM. Thanks.
>
> Reviewed-by: Naman Jain <[email protected]>
Applied. Thanks.
