On Wed, Dec 02, 2020 at 03:48:21PM +0100, Jürgen Groß wrote:
> I wanted to avoid the additional NOPs for the bare metal case.
Yeah, in that case it gets optimized to a single NOP:
[0.176692] SMP alternatives: 81a00068: [0:5) optimized NOPs: 0f 1f
44 00 00
which is nopl
On 02.12.20 13:32, Borislav Petkov wrote:
On Fri, Nov 20, 2020 at 12:46:22PM +0100, Juergen Gross wrote:
@@ -123,12 +115,15 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe,
SYM_L_GLOBAL)
* Try to use SYSRET instead of IRET if we're returning to
* a completely clean 64-bit
On Fri, Nov 20, 2020 at 12:46:22PM +0100, Juergen Gross wrote:
> @@ -123,12 +115,15 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe,
> SYM_L_GLOBAL)
>* Try to use SYSRET instead of IRET if we're returning to
>* a completely clean 64-bit userspace context. If we're not,
>
USERGS_SYSRET64 is used to return from a syscall via sysret, but
a Xen PV guest will nevertheless use the iret hypercall, as there
is no sysret PV hypercall defined.
So instead of testing all the prerequisites for doing a sysret and
then mangling the stack for Xen PV again for doing an iret just
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