On Thu, Mar 9, 2017 at 1:46 PM, Andy Lutomirski <l...@amacapital.net> wrote: > On Thu, Mar 9, 2017 at 1:43 PM, Andrew Cooper <andrew.coop...@citrix.com> > wrote: >> On 09/03/2017 21:32, Andy Lutomirski wrote: >>> On Mon, Mar 6, 2017 at 2:03 PM, Thomas Garnier <thgar...@google.com> wrote: >>> >>>> --- a/arch/x86/xen/enlighten.c >>>> +++ b/arch/x86/xen/enlighten.c >>>> @@ -710,7 +710,7 @@ static void load_TLS_descriptor(struct thread_struct >>>> *t, >>>> >>>> *shadow = t->tls_array[i]; >>>> >>>> - gdt = get_cpu_gdt_table(cpu); >>>> + gdt = get_cpu_gdt_rw(cpu); >>>> maddr = arbitrary_virt_to_machine(&gdt[GDT_ENTRY_TLS_MIN+i]); >>>> mc = __xen_mc_entry(0); >>> Boris, is this right? I don't see why it wouldn't be, but Xen is special. >> >> Under Xen PV, the GDT is already read-only at this point. (It is not >> safe to let the guest have writeable access to system tables, so the >> guest must relinquish write access to the frames wishing to be used as >> LDTs or GDTs.) >> >> The hypercall acts on the frame, not a virtual address, so either alias >> should be fine here. >> >> Under this new scheme, there will be two read-only aliases. I guess >> this is easier to maintain the split consistently across Linux, than to >> special case Xen PV because it doesn't need the second alias. >> > > I think we would gain nothing at all by special-casing Xen PV -- Linux > allocates the fixmap vaddrs at compile time, so we'd still allocate > them even if we rejigger all the helpers to avoid using them. >
I don't have any experience with Xen so it would be great if virtme can test it. I can remove the unused functions, I just thought they were useful shortcuts given some of them are already used. > --Andy -- Thomas _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
