Re: [Xen-devel] [PATCH RFC 3/4] x86: add invpcid.h

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Feb 15, 2018 at 12:15:56PM +0000, Andrew Cooper wrote:
> On 15/02/18 12:10, Wei Liu wrote:
> > Provide the functions needed for different modes.
> >
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> >  xen/include/asm-x86/invpcid.h | 61 
> > +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 61 insertions(+)
> >  create mode 100644 xen/include/asm-x86/invpcid.h
> >
> > diff --git a/xen/include/asm-x86/invpcid.h b/xen/include/asm-x86/invpcid.h
> > new file mode 100644
> > index 0000000000..7c307ecfc3
> > --- /dev/null
> > +++ b/xen/include/asm-x86/invpcid.h
> > @@ -0,0 +1,61 @@
> > +#ifndef _ASM_X86_INVPCID_H_
> > +#define _ASM_X86_INVPCID_H_
> > +
> > +#include <xen/types.h>
> > +
> > +#define INVPCID_TYPE_INDIV_ADDR      0
> > +#define INVPCID_TYPE_SINGLE_CTXT     1
> > +#define INVPCID_TYPE_ALL_INCL_GLOBAL 2
> > +#define INVPCID_TYPE_ALL_NON_GLOBAL  3
> > +
> > +struct invpcid_desc {
> > +    uint64_t pcid:12;
> > +    uint64_t reserved:52;
> > +    uint64_t addr;
> > +};
> > +
> > +static inline void invpcid(unsigned long pcid, unsigned long addr,
> > +                           unsigned long type)
> > +{
> > +    struct invpcid_desc desc = { .pcid = pcid, .addr = addr };
> > +
> > +    asm volatile ("invpcid (%0), %1"
> > +                  : : "r" (&desc), "r" (type) : "memory" );
> 
> invpcid %[desc], %[type]
> 
> And you can use [desc] "m" (desc) for the constraint.  The structure
> will be built on the stack, meaning that an %rsp based memory reference
> is more efficient than forcing the use of a register.

NP.

> 
> We probably also need a -DHAVE_GAS_INVPCID, as INVPCID is newer than
> some of the instruction groups we already check for.
> 

Or we can just use the byte code directly -- it is the same for both 64
and 32 bit, then manually specify the ModRM byte. That's what Linux
does.

Wei.

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