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

Re: [Xen-devel] [PATCH RFC for-4.13 08/10] xen/arm: alternative: add auto-nop infrastructure



On Fri, 27 Sep 2019, Volodymyr Babchuk wrote:
> Julien Grall writes:
> 
> > From: Mark Rutland <mark.rutland@xxxxxxx>
> >
> > In some cases, one side of an alternative sequence is simply a number of
> > NOPs used to balance the other side. Keeping track of this manually is
> > tedious, and the presence of large chains of NOPs makes the code more
> > painful to read than necessary.
> >
> > To ameliorate matters, this patch adds a new alternative_else_nop_endif,
> > which automatically balances an alternative sequence with a trivial NOP
> > sled.
> >
> > In many cases, we would like a NOP-sled in the default case, and
> > instructions patched in in the presence of a feature. To enable the NOPs
> > to be generated automatically for this case, this patch also adds a new
> > alternative_if, and updates alternative_else and alternative_endif to
> > work with either alternative_if or alternative_endif.
> >
> > The alternative infrastructure was originally ported from Linux. So this
> > is pretty much a straight backport from commit 792d47379f4d "arm64:
> > alternative: add auto-nop infrastructure". The only difference is the
> > nops macro added as not yet existing in Xen.
> >
> > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
> > [will: use new nops macro to generate nop sequences]
> > Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> > [julien: Add nops and port to Xen]
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

_______________________________________________
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®.