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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

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?

Wei.


>      rc = 0;
>      goto out;
>   error_out:
> -- 
> 1.9.5 (Apple Git-50.3)

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