On 05/07/2018 02:00 PM, van der Linden, Frank wrote:
> Hi Boris,
>
> Thanks for the feedback.
>
> On 5/7/18, 8:13 AM, "Boris Ostrovsky" <boris.ostrovsky@xxxxxxxxxx> wrote:
>
> > diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
> > index 6b424da1ce75..c78b3e8fb2e5 100644
> > --- a/arch/x86/xen/enlighten_hvm.c
> > +++ b/arch/x86/xen/enlighten_hvm.c
> > @@ -71,6 +71,19 @@ static void __init xen_hvm_init_mem_mapping(void)
> > {
> > early_memunmap(HYPERVISOR_shared_info, PAGE_SIZE);
> > HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn));
> > +
> > + /*
> > + * The virtual address of the shared_info page has changed, so
> > + * the vcpu_info pointer for VCPU 0 is now stale.
>
> Is it "has changed" or "has changed if kaslr is on"?
>
> It's "has changed". See commit 4ca83dcf4e3bc0c98836dbb97553792ca7ea5429 . It's a way to make kaslr work, but it's done regardless of whether it's enabled or not.
I completely forgot about this one.
>
> > + *
> > + * The prepare_boot_cpu callback will re-initialize it via
> > + * xen_vcpu_setup, but we can't rely on that to be called for
> > + * old Xen versions (xen_have_vector_callback == 0).
> > + *
> > + * It is, in any case, bad to have a stale vcpu_info pointer
> > + * so reset it now.
> > + */
> > + xen_vcpu_info_reset(0);
>
>
> Why not xen_vcpu_setup(0)?
>
> Basically, I wanted to be minimally invasive. xen_vcpu_setup does a little more work (tries to do the VCPU placement hypercall), and will be called later in any case. So doing just the basic xen_vcpu_info_reset for VCPU 0 seems like the best way to do it; it just re-iterates what is done for VCPU 0 earlier in boot, which is also a vcpu_info_reset.
OK, fair enough. This should go to stable as well I think (4.12+),
copying them.
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
