Re: [Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 20 Mar 2017, Stefano Stabellini wrote:
> On Mon, 13 Mar 2017, Wei Chen wrote:
> > We may have to isolate the SError between the context switch of
> > 2 vCPUs or may have to prevent slipping hypervisor SError to guest.
> 
> I thought the problem is not the risk of slipping hypervisor SErrors to
> guest, but the risk of slipping previous guest SErrors to the next
> guest. Is that right?

I can see from the following patches that both situations are a risk.
Although the patch could benefit from a better commit description:

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>



> > So we need a helper to synchronize SError before context switching
> > or returning to guest.
> > 
> > This function will be used by the later patches in this series, we
> > use "#if 0" to disable it temporarily to remove compiler warnning.
> > 
> > Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> > ---
> >  xen/arch/arm/traps.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> > index 44a0281..ee7865b 100644
> > --- a/xen/arch/arm/traps.c
> > +++ b/xen/arch/arm/traps.c
> > @@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct 
> > cpu_user_regs *regs)
> >      }
> >  }
> >  
> > +#if 0
> > +static void synchronize_serror(void)
> > +{
> > +    /* Synchronize against in-flight ld/st. */
> > +    dsb(sy);
> > +
> > +    /* A single instruction exception window */
> > +    isb();
> > +}
> > +#endif
> > +
> >  asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
> >  {
> >      enter_hypervisor_head(regs);
> > -- 
> > 2.7.4
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > https://lists.xen.org/xen-devel
> > 
> 

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