Re: [Xen-devel] HVMlite ABI specification DRAFT A

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 04/02/2016 22:21, Samuel Thibault wrote:
> Boris Ostrovsky, on Thu 04 Feb 2016 14:18:46 -0500, wrote:
>> On 02/04/2016 02:09 PM, Samuel Thibault wrote:
>>> Roger Pau Monné, on Thu 04 Feb 2016 18:48:14 +0100, wrote:
>>>>     struct hvm_start_info {
>>>>     #define HVM_START_MAGIC_VALUE 0x336ec578
>>>>         uint32_t magic;             /* Contains the magic value 0x336ec578 
>>>>       */
>>>>                                     /* ("xEn3" with the 0x80 bit of the 
>>>> "E" set).*/
>>>>         uint32_t flags;             /* SIF_xxx flags.                      
>>>>       */
>>>>         uint32_t cmdline_paddr;     /* Physical address of the command 
>>>> line.     */
>>>>         uint32_t nr_modules;        /* Number of modules passed to the 
>>>> kernel.   */
>>>>         uint32_t modlist_paddr;     /* Physical address of an array of     
>>>>       */
>>>>                                     /* hvm_modlist_entry.                  
>>>>       */
>>>>     };
>>> Mmm, don't we also need a description of the initial page table, so that
>>> the guest kernel knows which part of the memory it shouldn't use until
>>> having initialized its own page table?  Or is there none in the guest
>>> physical memory at startup of HVMlite mode?
>> We start with paging off.
> So a 32bit hypervisor *has* to use segmentation to protect itself from
> domU?

This is an HVM domain, so uses hardware virtualisation extensions.  It
is not like a PV guest.

The HVMLite binary is free to choose its width and paging mode.  All
this document states is that the entry point shall be 32bit flat unpaged
mode.

~Andrew

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