[v6][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

[v6][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

[Tiejun Chen]

Its used conveniently to create RMRR mapping in shared EPT case.

Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
---
 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));
+
+    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

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

[Chen, Tiejun]

Please ignore this since another patch is missed in this thread.

Sorry for any convenience.

Thanks
Tiejun

On 2014/7/30 9:26, Tiejun Chen wrote:
> Its used conveniently to create RMRR mapping in shared EPT case.
>
> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
> ---
>   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));
> +
> +    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);
>

[v6][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

[Tiejun Chen]

Its used conveniently to create RMRR mapping in shared EPT case.

Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
---
 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));
+
+    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

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

[Tian, Kevin]

> 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@intel.com>
> ---
>  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...

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

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

[Chen, Tiejun]

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@intel.com>
>> ---
>>   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
>
>

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

[Jan Beulich]

>>> On 01.08.14 at 00:29, <kevin.tian@intel.com> 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@intel.com>
>> ---
>>  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 good would looking at the guest's E820 table do here? Both
emulated MMIO ranges and the (supposed) exclusion ranges needed
for the RMRR would just be holes.

Jan

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

[Jan Beulich]

>>> On 01.08.14 at 04:25, <tiejun.chen@intel.com> wrote:
> On 2014/8/1 6:29, Tian, Kevin wrote:
>> 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;
> +        }
> +

That you're looking at the host E820, whereas Kevin asked about the
guest one. But see also my other reply just sent to him.

Jan

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

[Tian, Kevin]

> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: Thursday, July 31, 2014 11:42 PM
> 
> >>> On 01.08.14 at 00:29, <kevin.tian@intel.com> 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@intel.com>
> >> ---
> >>  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 good would looking at the guest's E820 table do here? Both
> emulated MMIO ranges and the (supposed) exclusion ranges needed
> for the RMRR would just be holes.
> 

You are right. E820 is memory oriented so we don't know whether the hole
has been used for emulated MMIO ranges...

Thanks
Kevin