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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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.

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

~Andrew

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