Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 15 Jul 2014 12:02:37 -0700 | Subject | Re: [RFC PATCH] x86_64,entry,xen: Do not invoke espfix64 on Xen |
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On Tue, Jul 15, 2014 at 12:00 PM, Boris Ostrovsky <boris.ostrovsky@oracle.com> wrote: > On 07/15/2014 01:22 PM, Andy Lutomirski wrote: >> >> On Tue, Jul 15, 2014 at 10:19 AM, Boris Ostrovsky >> <boris.ostrovsky@oracle.com> wrote: >>> >>> On 07/15/2014 12:23 PM, Andy Lutomirski wrote: >>>> >>>> >>>> diff --git a/arch/x86/kernel/paravirt_patch_64.c >>>> b/arch/x86/kernel/paravirt_patch_64.c >>>> index 3f08f34..a1da673 100644 >>>> --- a/arch/x86/kernel/paravirt_patch_64.c >>>> +++ b/arch/x86/kernel/paravirt_patch_64.c >>>> @@ -6,7 +6,6 @@ DEF_NATIVE(pv_irq_ops, irq_disable, "cli"); >>>> DEF_NATIVE(pv_irq_ops, irq_enable, "sti"); >>>> DEF_NATIVE(pv_irq_ops, restore_fl, "pushq %rdi; popfq"); >>>> DEF_NATIVE(pv_irq_ops, save_fl, "pushfq; popq %rax"); >>>> -DEF_NATIVE(pv_cpu_ops, iret, "iretq"); >>>> DEF_NATIVE(pv_mmu_ops, read_cr2, "movq %cr2, %rax"); >>>> DEF_NATIVE(pv_mmu_ops, read_cr3, "movq %cr3, %rax"); >>>> DEF_NATIVE(pv_mmu_ops, write_cr3, "movq %rdi, %cr3"); >>>> @@ -50,7 +49,6 @@ unsigned native_patch(u8 type, u16 clobbers, void >>>> *ibuf, >>>> PATCH_SITE(pv_irq_ops, save_fl); >>>> PATCH_SITE(pv_irq_ops, irq_enable); >>>> PATCH_SITE(pv_irq_ops, irq_disable); >>>> - PATCH_SITE(pv_cpu_ops, iret); >>> >>> >>> >>> Does this mean that we are no longer patching IRET with a jump to a >>> hypercall? >>> >> IIUC this means that, on native, we are no longer patching >> INTERRUPT_RETURN with an "iretq" instruction, so INTERRUPT_RETURN will >> remain a "jmp native_iret". I'm not sure why this patch was there in >> the first place. On Xen, it should still get patched with the >> hypercall (although someone should verify this). > > > Right, I missed the fact that this is native_patch. > > I did some light testing and it appears to work. Are you targeting this for > 3.16? >
That's the idea -- this, or some other fix, is needed for 3.16.
--Andy
> One way or the other we need to disable espfix64 on PV --- I discovered that > one of Peter's tests crashes the hypervisor. > > > -boris
-- Andy Lutomirski AMA Capital Management, LLC
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