Re: [Xen-devel] [PATCH v2 12/18] xen: setup Xen specific data for PVH

[Juergen Gross <jgross@xxxxxxxx>]

On 29/10/2018 13:57, Roger Pau Monné wrote:
> On Fri, Oct 19, 2018 at 06:39:50PM +0200, Juergen Gross wrote:
>> On 19/10/2018 18:10, Roger Pau Monné wrote:
>>> On Tue, Oct 09, 2018 at 01:03:11PM +0200, 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
>>>>
>>>> Set the RSDP address for the guest from the start_info page passed
>>>> as boot parameter.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>> ---
>>>>  grub-core/kern/i386/xen/pvh.c | 107 
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 107 insertions(+)
>>>>
>>>> diff --git a/grub-core/kern/i386/xen/pvh.c b/grub-core/kern/i386/xen/pvh.c
>>>> index b4933b454..93ed68245 100644
>>>> --- a/grub-core/kern/i386/xen/pvh.c
>>>> +++ b/grub-core/kern/i386/xen/pvh.c
>>>> @@ -24,6 +24,7 @@
>>>>  #include <grub/xen.h>
>>>>  #include <grub/i386/linux.h>
>>>>  #include <grub/machine/kernel.h>
>>>> +#include <xen/hvm/params.h>
>>>>  #include <xen/memory.h>
>>>>  
>>>>  struct xen_machine_mmap_entry
>>>> @@ -39,6 +40,7 @@ static struct { char _entry[32]; } hypercall_page[128]
>>>>    __attribute__ ((aligned (GRUB_XEN_PAGE_SIZE)));
>>>>  
>>>>  static grub_uint32_t xen_cpuid_base;
>>>> +static struct start_info grub_xen_start_page;
>>>>  static struct xen_machine_mmap_entry map[128];
>>>>  static unsigned int nr_map_entries;
>>>>  
>>>> @@ -104,6 +106,36 @@ 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_early_halt ();
>>>> +  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_early_halt ();
>>>> +  return addr;
>>>> +}
>>>> +
>>>>  static void
>>>>  grub_xen_sort_mmap (void)
>>>>  {
>>>> @@ -190,12 +222,87 @@ grub_xen_get_mmap (void)
>>>>    grub_xen_sort_mmap ();
>>>>  }
>>>>  
>>>> +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. */
>>>
>>> Doing this is kind of dangerous, what if you end up placing something
>>> on top of an MMIO region (either emulated or from a real passthrough
>>> device)?
>>
>> Shouldn't those be marked as "Reserved" in the memory map?
> 
> I don't think BARs are guaranteed to be in areas marked as reserved in
> the memory map. Unless you also scan for PCI devices and make sure
> there's no device with a BAR in the area you are attempting to
> populate I think the above is not safe.

So either I can add scanning the PCI bus (which wouldn't be too
hard IMO), or we require Xen tools to add memory map entries with
"Reserved" attribute for passed-through PCI device's MMIO-areas
(we can still do that as PCI pass-through for PVH isn't possible
yet AFAIK).


Juergen

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