Re: [Xen-devel] [PATCH v4 7/7] x86/tlb: use Xen L0 assisted TLB flush when available

[Wei Liu <wl@xxxxxxx>]

On Tue, Feb 11, 2020 at 03:06:21PM +0100, Roger Pau Monné wrote:
> On Tue, Feb 11, 2020 at 10:34:24AM +0000, Wei Liu wrote:
> > On Mon, Feb 10, 2020 at 06:28:29PM +0100, Roger Pau Monne wrote:
> > [...]
> > >  
> > >  struct hypervisor_ops {
> > > @@ -32,6 +34,8 @@ struct hypervisor_ops {
> > >      void (*resume)(void);
> > >      /* Fix up e820 map */
> > >      void (*e820_fixup)(struct e820map *e820);
> > > +    /* L0 assisted TLB flush */
> > > +    int (*flush_tlb)(const cpumask_t *mask, const void *va, unsigned int 
> > > order);
> > >  };
> > >  
> > >  #ifdef CONFIG_GUEST
> > > @@ -41,6 +45,14 @@ void hypervisor_setup(void);
> > >  int hypervisor_ap_setup(void);
> > >  void hypervisor_resume(void);
> > >  void hypervisor_e820_fixup(struct e820map *e820);
> > > +/*
> > > + * L0 assisted TLB flush.
> > > + * mask: cpumask of the dirty vCPUs that should be flushed.
> > > + * va: linear address to flush, or NULL for global flushes.
> > 
> > I was in the middle of writing my patch and noticed this.
> > 
> > I think NULL means "flushing the entire address space" here?
> 
> Yes, that's right. I didn't add a way to differentiate between global
> (ie: PGE mappings included) flushes and non-global flushes, so all
> calls are assumed to imply flushes of global mappings.
> 
> It might be better if you adapt it yourself to whatever is more suited
> for HyperV which has more selective flushes available. Xen only has an
> hypercall to request a global flush on all vCPUs.

OK. Thanks for confirming.

I will change this comment in my patch.

Wei.

> 
> Thanks, Roger.

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