[Xen-devel] Re: [RFC, PATCH 3/24] i386 Vmi interface definition

[Chris Wright <chrisw@xxxxxxxxxxxx>]

* Zachary Amsden (zach@xxxxxxxxxx) wrote:
> Master definition of VMI interface, including calls, constants, and
> interface version.

> +/* VROM call table definitions */
> +#define VROM_CALL_LEN             32
> +
> +typedef struct VROMCallEntry {
> +   char f[VROM_CALL_LEN];
> +} VROMCallEntry;

And the call entry is meant to be handled in whatever mechanism hypervisor
prefers for its entry points (ABI constraints notwithstanding) as in,
arbitrary software interrupt, or call gate, etc?  I guess for transparent
it has to, since those would be local calls.   Quite similar to the
hypercall entry point that Xen places on the hypercall_page, so easily
compatible.

> +typedef struct VROMHeader {
> +   VMI_UINT16          romSignature;             // option ROM signature
> +   VMI_INT8            romLength;                // ROM length in 512 byte 
> chunks
> +   unsigned char       romEntry[4];              // 16-bit code entry point
> +   VMI_UINT8           romPad0;                  // 4-byte align pad
> +   VMI_UINT32          vRomSignature;            // VROM identification 
> signature
> +   VMI_UINT8           APIVersionMinor;          // Minor version of API
> +   VMI_UINT8           APIVersionMajor;          // Major version of API
> +   VMI_UINT8           reserved0;                // Reserved for expansion
> +   VMI_UINT8           reserved1;                // Reserved for expansion
> +   VMI_UINT32          reserved2;                // Reserved for expansion
> +   VMI_UINT32          reserved3;                // Reserved for private use
> +   VMI_UINT16          pciHeaderOffset;          // Offset to PCI OPROM 
> header
> +   VMI_UINT16          pnpHeaderOffset;          // Offset to PnP OPROM 
> header
> +   VMI_UINT32          romPad3;                  // PnP reserverd / VMI 
> reserved
> +   VROMCallEntry       romCallReserved[3];       // Reserved call slots
> +} VROMHeader;

The document is slightly more descriptive.  The above reserved slots
are shown as:

        char            reserved[32];
        char            elfHeader[64];

But that's only 3 (0-2).  I think I'm missing some small bit of magic.

> +typedef struct VROMCallTable {
> +   VROMCallEntry    vromCall[128];           // @ 0x80: ROM calls 4-127
> +} VROMCallTable;

That comment eludes me.  Are 0-3 special somehow (IOW, I thought it was
just 0-2 as per above), and is it suggesting int 0x80?

> +// Historical 3.X revisions
> +//#define MIN_VMI_API_REV_MINOR              1 /* GetFlags_CLI is used */
> +//#define MIN_VMI_API_REV_MINOR              2 /* STI_SYSEXIT is used */
> +//#define MIN_VMI_API_REV_MINOR              3 /* IN/OUT are used */
> +//#define MIN_VMI_API_REV_MINOR         4 /* Deferred calls used */
> +//#define MIN_VMI_API_REV_MINOR              5 /* SetIOPLMask is used */
> +
> +// 4.X revisions
> +//#define MIN_VMI_API_REV_MINOR              0 /* IN/OUT binary compat */

Probably not the best format for keeping changelog entries.  Although
it's worth keeping the info somehwere in documentation perhaps.

thanks,
-chris

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