On Fri, Jan 15, 2021 at 06:24:10AM +0100, Jürgen Groß wrote: > On 14.01.21 20:40, Josh Poimboeuf wrote: > > It's kernel policy to not have (unannotated) indirect jumps because of > > Spectre v2. This one's probably harmless, but better safe than sorry. > > Convert it to a retpoline. > > > > Cc: Boris Ostrovsky <[email protected]> > > Cc: Juergen Gross <[email protected]> > > Signed-off-by: Josh Poimboeuf <[email protected]> > > --- > > arch/x86/platform/pvh/head.S | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S > > index 43b4d864817e..d87cebd08d32 100644 > > --- a/arch/x86/platform/pvh/head.S > > +++ b/arch/x86/platform/pvh/head.S > > @@ -16,6 +16,7 @@ > > #include <asm/boot.h> > > #include <asm/processor-flags.h> > > #include <asm/msr.h> > > +#include <asm/nospec-branch.h> > > #include <xen/interface/elfnote.h> > > __HEAD > > @@ -105,7 +106,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen) > > /* startup_64 expects boot_params in %rsi. */ > > mov $_pa(pvh_bootparams), %rsi > > mov $_pa(startup_64), %rax > > - jmp *%rax > > + JMP_NOSPEC rax > > I'd rather have it annotated only. > > Using ALTERNATIVE in very early boot code is just adding needless > clutter, as the retpoline variant won't ever be active.
Yeah, Andy pointed out something similar. I'll be changing this to an annotation. -- Josh
