Re: [Xen-devel] [v6][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2014/8/1 6:29, Tian, Kevin wrote:
> > From: Chen, Tiejun
> > Sent: Tuesday, July 29, 2014 6:36 PM
> >
> > Its used conveniently to create RMRR mapping in shared EPT case.
> >
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> > ---
> >   xen/arch/x86/mm/p2m.c     | 29 +++++++++++++++++++++++++++++
> >   xen/include/asm-x86/p2m.h |  3 +++
> >   2 files changed, 32 insertions(+)
> >
> > v6:
> >
> > * Refactor set_identity_p2m_entry to make sense
> >
> > v5:
> >
> > * Rename this function as set_identity_p2m_entry()
> > * Get mfn directly inside set_identity_p2m_entry()
> >
> > v4:
> >
> > * new patch to combine get and set together to create RMRR mapping.
> >
> > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> > index 642ec28..06bed7a 100644
> > --- a/xen/arch/x86/mm/p2m.c
> > +++ b/xen/arch/x86/mm/p2m.c
> > @@ -858,6 +858,35 @@ int set_mmio_p2m_entry(struct domain *d, unsigned
> > long gfn, mfn_t mfn)
> >       return set_typed_p2m_entry(d, gfn, mfn, p2m_mmio_direct);
> >   }
> >
> > +int set_identity_p2m_entry(struct domain *d, unsigned long gfn)
> > +{
> > +    p2m_type_t p2mt;
> > +    p2m_access_t a;
> > +    mfn_t mfn;
> > +    struct p2m_domain *p2m = p2m_get_hostp2m(d);
> > +    int ret = -EBUSY;
> > +
> > +    gfn_lock(p2m, gfn, 0);
> > +
> > +    mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);
> > +
> > +    if ( !mfn_valid(mfn) )
> > +        ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K,
> > p2m_mmio_direct,
> > +                            p2m_access_rw);
> > +    else if ( mfn_x(mfn) == gfn &&
> > +              p2mt == p2m_mmio_direct &&
> > +              a == p2m_access_rw )
> > +        ret = 0;
> > +    else
> > +        printk(XENLOG_G_WARNING
> > +               "Cannot identity map d%d:%lx, already mapped to %lx.\n",
> > +               d->domain_id, gfn, mfn_x(mfn));
> what about !mfn_valid but the GFN has been used for emulated MMIOs? w/o
> a guest e820 view you can't avoid overlapping by just looking at mfn...
What about the follows based on this patch?

@@ -865,14 +865,26 @@ int set_identity_p2m_entry(struct domain *d, 
unsigned long gfn)
     mfn_t mfn;
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
     int ret = -EBUSY;
+    u64 base_addr, end_addr;

     gfn_lock(p2m, gfn, 0);

     mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);

     if ( !mfn_valid(mfn) )
+    {
+        base_addr = gfn << PAGE_ORDER_4K;
+        end_addr = base_addr + PAGE_MASK;
+        if ( (!page_is_ram_type(paddr_to_pfn(base_addr), 
RAM_TYPE_RESERVED)) ||
+             (!page_is_ram_type(paddr_to_pfn(end_add), 
RAM_TYPE_RESERVED)) )
+        {
+            gfn_unlock(p2m, gfn, 0);
+            return ret;
+        }
+
         ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K, 
p2m_mmio_direct,
                             p2m_access_rw);
+    }
     else if ( mfn_x(mfn) == gfn &&
               p2mt == p2m_mmio_direct &&
               a == p2m_access_rw )

Note this chunk of codes just show what I want to do, without test.

Thanks
Tiejun

> Thanks
> Kevin
>
> > +
> > +    gfn_unlock(p2m, gfn, 0);
> > +
> > +    return ret;
> > +}
> > +
> >   /* Returns: 0 for success, -errno for failure */
> >   int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn)
> >   {
> > diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> > index 0ddbadb..d130f9a 100644
> > --- a/xen/include/asm-x86/p2m.h
> > +++ b/xen/include/asm-x86/p2m.h
> > @@ -536,6 +536,9 @@ int p2m_is_logdirty_range(struct p2m_domain *,
> > unsigned long start,
> >   int set_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn);
> >   int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn);
> >
> > +/* Set identity addresses in the p2m table (for pass-through) */
> > +int set_identity_p2m_entry(struct domain *d, unsigned long gfn);
> > +
> >   /* Add foreign mapping to the guest's p2m table. */
> >   int p2m_add_foreign(struct domain *tdom, unsigned long fgfn,
> >                       unsigned long gpfn, domid_t foreign_domid);
> > --
> > 1.9.1
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