Re: FAILED: patch "[PATCH] x86/nospec: Fix i386 RSB stuffing" failed to apply to 5.10-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Sep 02, 2022 at 04:26:57PM +0200, Ben Hutchings wrote:
> On Thu, 2022-09-01 at 11:43 +0200, Greg KH wrote:
> > On Mon, Aug 29, 2022 at 04:04:58PM +0200, Ben Hutchings wrote:
> > > On Mon, 2022-08-29 at 10:30 +0200, gregkh@linuxfoundation.org wrote:
> > > > The patch below does not apply to the 5.10-stable tree.
> > > > If someone wants it applied there, or to any other stable or longterm
> > > > tree, then please email the backport, including the original git commit
> > > > id to <stable@vger.kernel.org>.
> > > > 
> > > 
> > > You need commit 4e3aa9238277 "x86/nospec: Unwreck the RSB stuffing"
> > > before this one.  I've attached the backport of that for 5.10.  I
> > > haven't checked the older branches.
> > 
> > Great, thanks, this worked.  But the backport did not apply to 4.19, so
> > I will need that in order to take this one as well.
> 
> I've had a look at 5.4, and it's sufficiently different from upstream
> that I don't see how to move forward.
> 
> However, I also found that the PBRSB mitigation seems broken, as commit
> fc02735b14ff "KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS"
> was not backported (and would be hard to add).
> 
> So, perhaps it would be best to revert the backports of:
> 
> 2b1299322016 x86/speculation: Add RSB VM Exit protections
> ba6e31af2be9 x86/speculation: Add LFENCE to RSB fill sequence
> 
> in stable branches older than 5.10.

Why?  Is it because they do not work at all there, or are they causing
problems?

thanks,

greg k-h