[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86: use invpcid to do global flushing
>>> Juergen Gross <jgross@xxxxxxxx> 03/09/18 7:05 PM >>> >On 09/03/18 16:29, Jan Beulich wrote: >>>>> On 05.03.18 at 10:50, <wei.liu2@xxxxxxxxxx> wrote: >>> @@ -120,11 +121,24 @@ unsigned int flush_area_local(const void *va, >>> unsigned int flags) >>> else >>> { >>> u32 t = pre_flush(); >>> - unsigned long cr4 = read_cr4(); >>> >>> - write_cr4(cr4 & ~X86_CR4_PGE); >>> - barrier(); >>> - write_cr4(cr4); >>> + if ( !cpu_has_invpcid ) >>> + { >>> + unsigned long cr4 = read_cr4(); >>> + >>> + write_cr4(cr4 & ~X86_CR4_PGE); >>> + barrier(); >>> + write_cr4(cr4); >>> + } >>> + else >>> + { >>> + /* >>> + * Using invpcid to flush all mappings works >>> + * regardless of whether PCID is enabled or not. >>> + * It is faster than read-modify-write CR4. >>> + */ >>> + invpcid_flush_all(); >>> + } >> >> As just validly indicated by Jürgen, this is where my comment I >> gave to one of his patches actually belongs: This is correct for >> FLUSH_TLB_GLOBAL, but goes too far for FLUSH_TLB. > >And again it was so even before this patch. Not exactly - "before this patch" should include the state things were in before 32-bit code got removed. And that's where we had a proper separation between flushes including and excluding global entries. And now that we regain that ability, we should leverage it. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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