On 07/24/2018 08:45 AM, M. Vefa Bicakci wrote: > Commit d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits > adjustment corruption") has moved the query and calculation of the > x86_virt_bits and x86_phys_bits fields of the cpuinfo_x86 struct > from the get_cpu_cap function to a new function named > get_cpu_address_sizes. > > One of the call sites related to Xen PV VMs was unfortunately missed > in the aforementioned commit. This prevents successful boot-up of > kernel versions 4.17 and up in Xen PV VMs if CONFIG_DEBUG_VIRTUAL > is enabled, due to the following code path: > > enlighten_pv.c::xen_start_kernel > mmu_pv.c::xen_reserve_special_pages > page.h::__pa > physaddr.c::__phys_addr > physaddr.h::phys_addr_valid > > phys_addr_valid uses boot_cpu_data.x86_phys_bits to validate physical > addresses. boot_cpu_data.x86_phys_bits is no longer populated before > the call to xen_reserve_special_pages due to the aforementioned commit > though, so the validation performed by phys_addr_valid fails, which > causes __phys_addr to trigger a BUG, preventing boot-up. > > Signed-off-by: M. Vefa Bicakci <m.v.b@xxxxxxxxxx> > Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> > Cc: Juergen Gross <jgross@xxxxxxxx> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx > Cc: x86@xxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx # for v4.17 and up > Fixes: d94a155c59c9 ("x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment corruption") Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>