Re: [Xen-devel] [PATCH 6/6] Change MMU_PT_UPDATE_RESERVE_AD to support update page table for foreign domain

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

I'd pack an extra domid into the top 16 bits of the foreigndom parameter to
mmu_update(). Bottom 16 bits remain foreign owner of data page. Upper 16
bits, if non-zero, are foreign owner of pt page (we could make this field +1
so that dom0 can be encoded as well).

 -- Keir

On 01/06/2009 07:24, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> I want to clarify that this patch need more discussion because there is no
> clear way to distinguish if the page table address (i.e. address passed in
> req[:2] ) is owned by the current domain or by the foreign domain. So I just
> try to check if mfn_valid(), but I suspect if this is the right method.
> 
> Thanks
> Yunhong Jiang
> 
> xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote:
>> foreign domain
>> 
>> Currently MMU_PT_UPDATE_RESERVE_AD support only update page
>> table for current domain. This patch add support for foreign
>> domain also.
>> 
>> Signed-off-by: Jiang, Yunhong <yunhong.jiang@xxxxxxxxx> Update
>> the page table update hypercall
>> 
>> diff -r f6457425560b xen/arch/x86/mm.c
>> --- a/xen/arch/x86/mm.c Wed May 27 03:22:43 2009 +0800
>> +++ b/xen/arch/x86/mm.c Wed May 27 03:40:38 2009 +0800 @@ -110,6
>> +110,7 @@ #include <asm/hypercall.h>
>> #include <asm/shared.h>
>> #include <public/memory.h>
>> +#include <public/sched.h>
>> #include <xsm/xsm.h>
>> #include <xen/trace.h>
>> 
>> @@ -2990,7 +2991,8 @@ int do_mmu_update(
>>     struct page_info *page;
>>     int rc = 0, okay = 1, i = 0;
>>     unsigned int cmd, done = 0;
>> -    struct domain *d = current->domain;
>> +    struct domain *d = current->domain, *pt_owner = NULL;
>> +    struct vcpu *v = current;
>>     struct domain_mmap_cache mapcache;
>> 
>>     if ( unlikely(count & MMU_UPDATE_PREEMPTED) )
>> @@ -3051,10 +3053,35 @@ int do_mmu_update(
>>             gmfn = req.ptr >> PAGE_SHIFT;
>>             mfn = gmfn_to_mfn(d, gmfn);
>> 
>> -            if ( unlikely(!get_page_from_pagenr(mfn, d)) )
>> +            if (!mfn_valid(mfn))
>> +                mfn = gmfn_to_mfn(FOREIGNDOM, gmfn);
>> +            if (!mfn_valid(mfn))
>>             {
>>                 MEM_LOG("Could not get page for normal update");
>> break; +            }
>> +
>> +            pt_owner =
>> page_get_owner_and_reference(mfn_to_page(mfn)); + +            if (
>> pt_owner != d ) +            {
>> +                if ( pt_owner == FOREIGNDOM )
>> +                {
>> +                    spin_lock(&FOREIGNDOM->shutdown_lock);
>> +                    if ( !IS_PRIV(d) ||
>> +                         !FOREIGNDOM->is_shut_down ||
>> +                          (FOREIGNDOM->shutdown_code !=
>> SHUTDOWN_suspend) ) +                    {
>> +                        spin_unlock(&FOREIGNDOM->shutdown_lock);
>> +                        rc = -EPERM;
>> +                        break;
>> +                    }
>> +                    v = FOREIGNDOM->vcpu[0];
>> +                }else
>> +                {
>> +                    rc = -EPERM;
>> +                    break;
>> +                }
>>             }
>> 
>>             va = map_domain_page_with_cache(mfn, &mapcache);
>> @@ -3070,24 +3097,21 @@ int do_mmu_update(
>>                 {
>>                     l1_pgentry_t l1e = l1e_from_intpte(req.val);
>>                     okay = mod_l1_entry(va, l1e, mfn,
>> -                                        cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD,
>> -                                        current);
>> +                                        cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, v);
>>                 }
>>                 break;
>>                 case PGT_l2_page_table:
>>                 {
>>                     l2_pgentry_t l2e = l2e_from_intpte(req.val);
>>                     okay = mod_l2_entry(va, l2e, mfn,
>> -                                        cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD,
>> -                                        current);
>> +                                        cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, v);
>>                 }
>>                 break;
>>                 case PGT_l3_page_table:
>>                 {
>>                     l3_pgentry_t l3e = l3e_from_intpte(req.val);
>>                     rc = mod_l3_entry(va, l3e, mfn,
>> -                                      cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, 1,
>> -                                      current);
>> +                                      cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, 1, v);
>>                     okay = !rc;
>>                 }
>>                 break;
>> @@ -3096,8 +3120,7 @@ int do_mmu_update(
>>                 {
>>                     l4_pgentry_t l4e = l4e_from_intpte(req.val);
>>                     rc = mod_l4_entry(va, l4e, mfn,
>> -                                      cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, 1,
>> -                                      current);
>> +                                      cmd ==
>> MMU_PT_UPDATE_PRESERVE_AD, 1, v);
>>                     okay = !rc;
>>                 }
>>                 break;
>> @@ -3105,7 +3128,7 @@ int do_mmu_update(
>>                 case PGT_writable_page:
>>                     perfc_incr(writable_mmu_updates);
>>                     okay = paging_write_guest_entry(
>> -                        current, va, req.val, _mfn(mfn));
>> +                        v, va, req.val, _mfn(mfn));
>>                 break; }
>>                 page_unlock(page);
>> @@ -3116,11 +3139,13 @@ int do_mmu_update(
>>             {
>>                 perfc_incr(writable_mmu_updates);
>>                 okay = paging_write_guest_entry(
>> -                    current, va, req.val, _mfn(mfn));
>> +                    v, va, req.val, _mfn(mfn));
>>                 put_page_type(page);
>>             }
>> 
>>             unmap_domain_page_with_cache(va, &mapcache);
>> +            if (pt_owner != d)
>> +                spin_unlock(&FOREIGNDOM->shutdown_lock);
>>             put_page(page); break;
>> 
>> diff -r f6457425560b xen/include/public/xen.h
>> --- a/xen/include/public/xen.h Wed May 27 03:22:43 2009 +0800
>> +++ b/xen/include/public/xen.h Wed May 27 03:26:46 2009 +0800
>> @@ -170,6 +170,8 @@ DEFINE_XEN_GUEST_HANDLE(xen_pfn_t);
>>  * table entry is valid/present, the mapped frame must belong
>> to the FD, if
>>  * an FD has been specified. If attempting to map an I/O page then the
>>  * caller assumes the privilege of the FD.
>> + * The page table entry normally belongs to the calling
>> domain. Otherwise it
>> + * should belong to the FD and the FD should be suspended already
>>  * FD == DOMID_IO: Permit /only/ I/O mappings, at the priv
>> level of the caller.
>>  * FD == DOMID_XEN: Map restricted areas of Xen's heap space.
>>  * ptr[:2]  -- Machine address of the page-table entry to modify.



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