Re: [Xen-devel] [PATCH v4 1/3] x86/hypervisor: pass flags to hypervisor_flush_tlb

[Wei Liu <wl@xxxxxxx>]

On Tue, Mar 10, 2020 at 10:58:09AM +0100, Jan Beulich wrote:
> On 09.03.2020 18:25, Wei Liu wrote:
> > On Mon, Mar 09, 2020 at 05:38:12PM +0100, Jan Beulich wrote:
> >> On 19.02.2020 12:44, Wei Liu wrote:
> >>> --- a/xen/include/asm-x86/flushtlb.h
> >>> +++ b/xen/include/asm-x86/flushtlb.h
> >>> @@ -123,6 +123,9 @@ void switch_cr3_cr4(unsigned long cr3, unsigned long 
> >>> cr4);
> >>>   /* Flush all HVM guests linear TLB (using ASID/VPID) */
> >>>  #define FLUSH_GUESTS_TLB 0x4000
> >>>  
> >>> +#define FLUSH_TLB_FLAGS_MASK (FLUSH_TLB | FLUSH_TLB_GLOBAL | 
> >>> FLUSH_VA_VALID | \
> >>> +                              FLUSH_ORDER_MASK)
> >>
> >> I don't think FLUSH_ORDER_MASK should be part of this, as it's not
> >> exclusively TLB-flush related.
> > 
> > My intention was to capture all flags pertinent to TLB flushes. I didn't
> > mean they were exclusively TLB flush related.
> 
> That's what I understood, but the result is leading to possible ambiguity.
> Thinking about it again, ...
> 
> > I can remove the order mask from the list of flags. Not a big deal.
> 
> ... I'm afraid I also have to ask for FLUSH_VA_VALID to be dropped,
> as that one's not TLB flush related at all. Instead it identifies
> whether the linear address provided _still has_ a valid mapping
> (rather than there being an address provided at all), such that
> CLFLUSH bases cache flushing would be usable. At that point I
> wonder whether the separate constant is still of much use at all.

Sure, I don't mind dropping it altogether.

Wei.

> 
> Jan

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