Re: [Xen-devel] [PATCH v4 13/19] xen: setup Xen specific data for PVH

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Fri, Nov 02, 2018 at 01:37:32PM +0100, Juergen Gross wrote:
> Initialize the needed Xen specific data. This is:
>
> - the Xen start of day page containing the console and Xenstore ring
>   page PFN and event channel
> - the grant table
> - the shared info page
>
> Write back the possibly modified memory map to the hypervisor in case
> the guest is reading it from there again.
>
> Set the RSDP address for the guest from the start_info page passed
> as boot parameter.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> V4: write back memory map to Xen (Roger Pau Monné)
> ---
>  grub-core/kern/i386/xen/pvh.c | 119 
> ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 119 insertions(+)
>
> diff --git a/grub-core/kern/i386/xen/pvh.c b/grub-core/kern/i386/xen/pvh.c
> index 442351d1d..d74301f92 100644
> --- a/grub-core/kern/i386/xen/pvh.c
> +++ b/grub-core/kern/i386/xen/pvh.c
> @@ -27,6 +27,7 @@
>  #include <grub/i386/linux.h>
>  #include <grub/machine/kernel.h>
>  #include <grub/machine/memory.h>
> +#include <xen/hvm/params.h>
>  #include <xen/memory.h>
>
>  #define XEN_CONSOLE_PORT      0xe9
> @@ -39,6 +40,7 @@ static char hypercall_page[GRUB_XEN_PAGE_SIZE]
>    __attribute__ ((aligned (GRUB_XEN_PAGE_SIZE)));
>
>  static grub_uint32_t xen_cpuid_base;
> +static struct start_info grub_xen_start_page;
>  static struct grub_e820_mmap_entry map[XEN_MEMORY_MAP_SIZE];
>  static unsigned int nr_map_entries;
>
> @@ -100,6 +102,36 @@ grub_xen_hypercall (grub_uint32_t callno, grub_uint32_t 
> a0,
>    return __res;
>  }
>
> +static grub_uint32_t
> +grub_xen_get_param (int idx)
> +{
> +  struct xen_hvm_param xhv;
> +  int r;
> +
> +  xhv.domid = DOMID_SELF;
> +  xhv.index = idx;
> +  r = grub_xen_hypercall (__HYPERVISOR_hvm_op, HVMOP_get_param,
> +                       (grub_uint32_t) (&xhv), 0, 0, 0, 0);
> +  if (r < 0)
> +    grub_xen_panic ("Could not get parameter from Xen.\n");

I would replace "." with "!" here and in the other grub_xen_panic() calls.

> +  return xhv.value;
> +}
> +
> +static void *
> +grub_xen_add_physmap (unsigned int space, void *addr)
> +{
> +  struct xen_add_to_physmap xatp;
> +
> +  xatp.domid = DOMID_SELF;
> +  xatp.idx = 0;
> +  xatp.space = space;
> +  xatp.gpfn = (grub_addr_t) addr >> GRUB_XEN_LOG_PAGE_SIZE;
> +  if (grub_xen_hypercall (__HYPERVISOR_memory_op, XENMEM_add_to_physmap,
> +                       (grub_uint32_t) (&xatp), 0, 0, 0, 0))
> +    grub_xen_panic ("Memory_op hypercall failed.\n");
> +  return addr;
> +}
> +
>  static void
>  grub_xen_sort_mmap (void)
>  {
> @@ -255,12 +287,99 @@ grub_xen_get_mmap (void)
>    grub_xen_sort_mmap ();
>  }
>
> +static void
> +grub_xen_set_mmap (void)
> +{
> +  struct xen_foreign_memory_map memmap;
> +
> +  memmap.domid = DOMID_SELF;
> +  memmap.map.nr_entries = nr_map_entries;
> +  set_xen_guest_handle (memmap.map.buffer, map);
> +  grub_xen_hypercall (__HYPERVISOR_memory_op, XENMEM_set_memory_map,
> +                   (grub_uint32_t) (&memmap), 0, 0, 0, 0);
> +}
> +
> +static grub_uint64_t
> +grub_xen_find_page (grub_uint64_t start)
> +{
> +  unsigned int i, j;
> +  grub_uint64_t last = start;
> +
> +  /* Try to find a e820 map hole below 4G. */
> +  for (i = 0; i < nr_map_entries; i++)
> +    {
> +      if (last > map[i].addr + map[i].len)
> +     continue;
> +      if (last < map[i].addr)
> +     return last;
> +      if ((map[i].addr >> 32) || ((map[i].addr + map[i].len) >> 32))
> +     break;
> +      last = map[i].addr + map[i].len;
> +    }

It took me some time to get why it works. AIUI this is due to proper
start/end alignment. Right? So, please say about that in the comment.

And I would like to hear a word from Roger here too. If he is OK
with the patch you can add my RB too.

Daniel

> +    if (i == nr_map_entries)
> +      return last;
> +
> +  /* No hole found, use the highest RAM page below 4G and reserve it. */
> +  if (nr_map_entries == ARRAY_SIZE (map))
> +    grub_xen_panic ("Memory map size limit reached.\n");
> +  for (i = 0, j = 0; i < nr_map_entries; i++)
> +    {
> +      if (map[i].type != GRUB_MEMORY_AVAILABLE)
> +     continue;
> +      if (map[i].addr >> 32)
> +     break;
> +      j = i;
> +      if ((map[i].addr + map[i].len) >> 32)
> +     break;
> +    }
> +  if (map[j].type != GRUB_MEMORY_AVAILABLE)
> +    grub_xen_panic ("No free memory page found.\n");
> +  if ((map[j].addr + map[j].len) >> 32)
> +    last = (1ULL << 32) - GRUB_XEN_PAGE_SIZE;
> +  else
> +    last = map[j].addr + map[j].len - GRUB_XEN_PAGE_SIZE;
> +  map[nr_map_entries].addr = last;
> +  map[nr_map_entries].len = GRUB_XEN_PAGE_SIZE;
> +  map[nr_map_entries].type = GRUB_MEMORY_RESERVED;
> +  nr_map_entries++;
> +  grub_xen_sort_mmap ();
> +
> +  return last;
> +}
> +
>  void
>  grub_xen_setup_pvh (void)
>  {
> +  grub_addr_t par;
> +
>    grub_xen_cpuid_base ();
>    grub_xen_setup_hypercall_page ();
>    grub_xen_get_mmap ();
> +
> +  /* Setup Xen data. */
> +  grub_xen_start_page_addr = &grub_xen_start_page;
> +
> +  par = grub_xen_get_param (HVM_PARAM_CONSOLE_PFN);
> +  grub_xen_start_page_addr->console.domU.mfn = par;
> +  grub_xen_xcons = (void *) (grub_addr_t) (par << GRUB_XEN_LOG_PAGE_SIZE);
> +  par = grub_xen_get_param (HVM_PARAM_CONSOLE_EVTCHN);
> +  grub_xen_start_page_addr->console.domU.evtchn = par;
> +
> +  par = grub_xen_get_param (HVM_PARAM_STORE_PFN);
> +  grub_xen_start_page_addr->store_mfn = par;
> +  grub_xen_xenstore = (void *) (grub_addr_t) (par << GRUB_XEN_LOG_PAGE_SIZE);
> +  par = grub_xen_get_param (HVM_PARAM_STORE_EVTCHN);
> +  grub_xen_start_page_addr->store_evtchn = par;
> +
> +  par = grub_xen_find_page (0);
> +  grub_xen_grant_table = grub_xen_add_physmap (XENMAPSPACE_grant_table,
> +                                            (void *) par);
> +  par = grub_xen_find_page (par + GRUB_XEN_PAGE_SIZE);
> +  grub_xen_shared_info = grub_xen_add_physmap (XENMAPSPACE_shared_info,
> +                                            (void *) par);
> +  grub_xen_set_mmap ();
> +
> +  grub_rsdp_addr = pvh_start_info->rsdp_paddr;
>  }
>
>  grub_err_t
> --
> 2.16.4

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