Re: [Xen-devel] [PATCH v4 25/31] xen: allow HVM guests to use XENMEM_memory_map

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

El 07/08/15 a les 14.22, Wei Liu ha escrit:
> On Fri, Aug 07, 2015 at 12:18:02PM +0200, Roger Pau Monne wrote:
>> Enable this hypercall for HVM guests in order to fetch the e820 memory
>> map in the absence of an emulated BIOS. The memory map is populated and
>> notified to Xen in arch_setup_meminit_hvm.
>>
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>> Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> ---
>>  tools/libxc/xc_dom_x86.c | 29 ++++++++++++++++++++++++++++-
>>  1 file changed, 28 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
>> index b587b12..87bce6e 100644
>> --- a/tools/libxc/xc_dom_x86.c
>> +++ b/tools/libxc/xc_dom_x86.c
>> @@ -1205,6 +1205,7 @@ static int check_mmio_hole(uint64_t start, uint64_t 
>> memsize,
>>          return 1;
>>  }
>>  
>> +#define MAX_E820_ENTRIES    128
>>  static int meminit_hvm(struct xc_dom_image *dom)
>>  {
>>      unsigned long i, vmemid, nr_pages = dom->total_pages;
>> @@ -1225,6 +1226,8 @@ static int meminit_hvm(struct xc_dom_image *dom)
>>      unsigned int nr_vmemranges, nr_vnodes;
>>      xc_interface *xch = dom->xch;
>>      uint32_t domid = dom->guest_domid;
>> +    struct e820entry entries[MAX_E820_ENTRIES];
>> +    int e820_index = 0;
>>  
>>      if ( nr_pages > target_pages )
>>          memflags |= XENMEMF_populate_on_demand;
>> @@ -1275,6 +1278,13 @@ static int meminit_hvm(struct xc_dom_image *dom)
>>          vnode_to_pnode = dom->vnode_to_pnode;
>>      }
>>  
>> +    /* Add one additional memory range to account for the VGA hole */
>> +    if ( (nr_vmemranges + (dom->emulation ? 1 : 0)) > MAX_E820_ENTRIES )
>> +    {
>> +        DOMPRINTF("Too many memory ranges");
>> +        goto error_out;
>> +    }
>> +
>>      total_pages = 0;
>>      p2m_size = 0;
>>      for ( i = 0; i < nr_vmemranges; i++ )
>> @@ -1363,9 +1373,13 @@ static int meminit_hvm(struct xc_dom_image *dom)
>>       * Under 2MB mode, we allocate pages in batches of no more than 8MB to 
>>       * ensure that we can be preempted and hence dom0 remains responsive.
>>       */
>> -    if ( dom->emulation )
>> +    if ( dom->emulation ) {
>>          rc = xc_domain_populate_physmap_exact(
>>              xch, domid, 0xa0, 0, memflags, &dom->p2m_host[0x00]);
>> +        entries[e820_index].addr = 0;
>> +        entries[e820_index].size = 0xa0 << PAGE_SHIFT;
>> +        entries[e820_index++].type = E820_RAM;
>> +    }
>>  
>>      stat_normal_pages = 0;
>>      for ( vmemid = 0; vmemid < nr_vmemranges; vmemid++ )
>> @@ -1392,6 +1406,12 @@ static int meminit_hvm(struct xc_dom_image *dom)
>>          else
>>              cur_pages = vmemranges[vmemid].start >> PAGE_SHIFT;
>>  
>> +        /* Build an e820 map. */
>> +        entries[e820_index].addr = cur_pages << PAGE_SHIFT;
>> +        entries[e820_index].size = vmemranges[vmemid].end -
>> +                                   entries[e820_index].addr;
>> +        entries[e820_index++].type = E820_RAM;
>> +
>>          while ( (rc == 0) && (end_pages > cur_pages) )
>>          {
>>              /* Clip count to maximum 1GB extent. */
>> @@ -1509,6 +1529,13 @@ static int meminit_hvm(struct xc_dom_image *dom)
>>      DPRINTF("  2MB PAGES: 0x%016lx\n", stat_2mb_pages);
>>      DPRINTF("  1GB PAGES: 0x%016lx\n", stat_1gb_pages);
>>  
>> +    rc = xc_domain_set_memory_map(xch, domid, entries, e820_index);
>> +    if ( rc != 0 )
>> +    {
>> +        DOMPRINTF("unable to set memory map.");
>> +        goto error_out;
>> +    }
>> +
> 
> I think in RDM series there is already a memory map generated in libxl.
> 
> You might want to move this to libxl, which is supposed to be the
> arbitrator of what a guest should look like.
> 
> What do you think?

I would like to do that, the only problem I see is that libxl doesn't
have any notion of the "special pages", so it doesn't know the size of
the hole it has to made. I guess one solution would be moving the
defines at the top of xc_dom_x86.c to a public libxc header so libxl can
pick up the size and position of the hole.

Roger.


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