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


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Juergen Gross <jgross@xxxxxxxx>
  • Date: Tue, 30 Oct 2018 13:12:07 +0100
  • Autocrypt: addr=jgross@xxxxxxxx; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb
  • Cc: hans@xxxxxxxxxxx, grub-devel@xxxxxxx, daniel.kiper@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxx, phcoder@xxxxxxxxx
  • Delivery-date: Tue, 30 Oct 2018 12:12:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 30/10/2018 12:23, Roger Pau Monné wrote:
> On Mon, Oct 29, 2018 at 03:19:34PM +0100, Juergen Gross wrote:
>> 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).
> 
> Ideally (and that's kind of far away from what we are now), I would
> like to have an interface to request Xen for a range of gfns available
> to map stuff in them (grants/foreign mappings/shared page...). That
> interface could be a simple hypercall that would return such range, or
> an hypercall that could be used to fetch something akin to an
> 'extended memory map' with specific Xen information (like such
> regions).
> 
> In both cases this requires Xen having a clearer picture of the p2m,
> because any of the above solutions cannot rely on scanning the p2m
> table in order to figure out what's where.
> 
> So the only change I would request is that if you use a RAM page you
> update the memory map stored in Xen to match the new layout, by using
> the XENMEM_set_memory_map hypercall.

Okay, this is simple.

Nevertheless I'm adding the already finished patch for scanning the
PCI devices to find MMIO areas.


Juergen

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