Re: [PATCH 5/9] x86/uv: Use the right tlbflush API

[Andrew Banman]

On 12/5/17 3:27 PM, Peter Zijlstra wrote:
> On Tue, Dec 05, 2017 at 03:09:48PM -0600, Andrew Banman wrote:
> > On 12/5/17 6:34 AM, Peter Zijlstra wrote:
> > > Since uv_flush_tlb_others() implements flush_tlb_others() which is
> > > about flushing user mappings, we should use __flush_tlb_single(),
> > > which too is about flushing user mappings.
> > >
> > > Cc: Andrew Banman<abanman@xxxxxxx>
> > > Cc: Mike Travis<mike.travis@xxxxxxx>
> > > Signed-off-by: Peter Zijlstra (Intel)<peterz@xxxxxxxxxxxxx>
> > > ---
> > >   arch/x86/platform/uv/tlb_uv.c |    2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > --- a/arch/x86/platform/uv/tlb_uv.c
> > > +++ b/arch/x86/platform/uv/tlb_uv.c
> > > @@ -299,7 +299,7 @@ static void bau_process_message(struct m
> > >   		local_flush_tlb();
> > >   		stat->d_alltlb++;
> > >   	} else {
> > > -		__flush_tlb_one(msg->address);
> > > +		__flush_tlb_single(msg->address);
> > >   		stat->d_onetlb++;
> > >   	}
> > >   	stat->d_requestee++;
> >
> > This looks like the right thing to do. We'll be testing it and complain later if
> > we find any problems, but I'm not expecting any since this patch looks to
> > maintain our status quo.
>
> Well, with KPTI (the-patch-set-formerly-known-as-kaiser), there will be
> a distinct difference between the two.
>
> With KPTI __flush_tlb_one() would end up invalidating all kernel
> mappings while __flush_tlb_single() will end up only invalidating the
> user mappings of the current mm.

Right! Now the KPTI __flush_tlb_single() equals the old
__flush_tlb_one(), less the call to count_vm_tlb_event().

ACK