[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 1/2] x86/entry/64: Do not clear %rbx under Xen



On 07/21/2018 05:19 PM, Boris Ostrovsky wrote:
On 07/21/2018 03:49 PM, M. Vefa Bicakci wrote:
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index c7449f377a77..96e8ff34129e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1129,7 +1129,7 @@ ENTRY(xen_failsafe_callback)
        addq    $0x30, %rsp
        UNWIND_HINT_IRET_REGS
        pushq   $-1 /* orig_ax = -1 => not a system call */
-       PUSH_AND_CLEAR_REGS
+       PUSH_AND_CLEAR_REGS clear_rbx=0


Do we need this at all? We are returning from the hypervisor here.

-boris

        ENCODE_FRAME_POINTER
        jmp     error_exit
  END(xen_failsafe_callback)

Hello Boris,

If you are referring to the PUSH_AND_CLEAR_REGS macro itself, I am not sure;
however, not clearing the RBX register seemed to resolve the issues mentioned
in the commit message for me. Given Andy's comment though, I believe that the
approach in this patch may not be correct.

Thank you,

Vefa

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.