[PATCH] altp2m: Allow the hostp2m to be shared

[PATCH] altp2m: Allow the hostp2m to be shared

[Tamas K Lengyel]

Don't propagate altp2m changes from ept_set_entry for memshare as memshare
already has the lock. We call altp2m propagate changes once memshare
successfully finishes. Also, allow the hostp2m entries to be of type
p2m_ram_shared.

Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
---
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
---
 xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
 xen/arch/x86/mm/p2m-ept.c     |  2 +-
 xen/arch/x86/mm/p2m.c         |  7 +++----
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index a522423..d5b4b2d 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -35,6 +35,7 @@
 #include <asm/p2m.h>
 #include <asm/atomic.h>
 #include <asm/event.h>
+#include <asm/altp2m.h>
 #include <xsm/xsm.h>
 
 #include "mm-locks.h"
@@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd, unsigned long sgfn, shr_handle_t
     /* We managed to free a domain page. */
     atomic_dec(&nr_shared_mfns);
     atomic_inc(&nr_saved_mfns);
+
+    if( altp2m_active(cd) )
+    {
+        p2m_access_t a;
+        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
+        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
+        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, PAGE_ORDER_4K,
+                                    p2m_ram_shared, a);
+    }
+
     ret = 0;
     
 err_out:
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 3cb6868..1ac3018 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -846,7 +846,7 @@ out:
     if ( is_epte_present(&old_entry) )
         ept_free_entry(p2m, &old_entry, target);
 
-    if ( rc == 0 && p2m_is_hostp2m(p2m) )
+    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
         p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt, p2ma);
 
     return rc;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index b3fce1b..d2aebf7 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
     /* Check host p2m if no valid entry in alternate */
     if ( !mfn_valid(mfn) )
     {
-        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
-                              P2M_ALLOC | P2M_UNSHARE, &page_order, NULL);
+        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order, NULL);
 
         rc = -ESRCH;
-        if ( !mfn_valid(mfn) || t != p2m_ram_rw )
+        if ( !mfn_valid(mfn) || (t != p2m_ram_rw && t != p2m_ram_shared) )
             return rc;
 
         /* If this is a superpage, copy that first */
@@ -1760,7 +1759,7 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
     }
 
     return ap2m->set_entry(ap2m, gfn_l, mfn, PAGE_ORDER_4K, t, a,
-                         (current->domain != d));
+                           (current->domain != d));
 }
 
 /*
-- 
2.1.4


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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[Konrad Rzeszutek Wilk]

Sadly I only have little nitpicks. Feel free to ignore them.

> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
> index a522423..d5b4b2d 100644
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -35,6 +35,7 @@
>  #include <asm/p2m.h>
>  #include <asm/atomic.h>
>  #include <asm/event.h>
> +#include <asm/altp2m.h>
>  #include <xsm/xsm.h>
>  
>  #include "mm-locks.h"
> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd, unsigned long sgfn, shr_handle_t
>      /* We managed to free a domain page. */
>      atomic_dec(&nr_shared_mfns);
>      atomic_inc(&nr_saved_mfns);
> +
> +    if( altp2m_active(cd) )

Missing space.
> +    {
> +        p2m_access_t a;

Newline.
> +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
> +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
> +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, PAGE_ORDER_4K,
> +                                    p2m_ram_shared, a);
> +    }
> +
>      ret = 0;
>      
>  err_out:
> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> index 3cb6868..1ac3018 100644
> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -846,7 +846,7 @@ out:
>      if ( is_epte_present(&old_entry) )
>          ept_free_entry(p2m, &old_entry, target);
>  
> -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
> +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
>          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt, p2ma);
>  
>      return rc;
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index b3fce1b..d2aebf7 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
>      /* Check host p2m if no valid entry in alternate */
>      if ( !mfn_valid(mfn) )
>      {
> -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
> -                              P2M_ALLOC | P2M_UNSHARE, &page_order, NULL);
> +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order, NULL);
>  
>          rc = -ESRCH;
> -        if ( !mfn_valid(mfn) || t != p2m_ram_rw )
> +        if ( !mfn_valid(mfn) || (t != p2m_ram_rw && t != p2m_ram_shared) )

Would it be easier to read if there were more of ()?

>              return rc;
>  
>          /* If this is a superpage, copy that first */
> @@ -1760,7 +1759,7 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
>      }
>  
>      return ap2m->set_entry(ap2m, gfn_l, mfn, PAGE_ORDER_4K, t, a,
> -                         (current->domain != d));
> +                           (current->domain != d));

That looks like a cleanup? Perhaps a different patch?

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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[George Dunlap]

On 21/04/16 18:10, Tamas K Lengyel wrote:
> Don't propagate altp2m changes from ept_set_entry for memshare as memshare
> already has the lock. We call altp2m propagate changes once memshare
> successfully finishes. Also, allow the hostp2m entries to be of type
> p2m_ram_shared.
> 
> Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>

Sorry for the delay in reviewing -- trying to get my head back around
the altp2m code.  On the whole looks reasonable, but one question...

> ---
> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> Cc: Keir Fraser <keir@xen.org>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: Jun Nakajima <jun.nakajima@intel.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> ---
>  xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
>  xen/arch/x86/mm/p2m-ept.c     |  2 +-
>  xen/arch/x86/mm/p2m.c         |  7 +++----
>  3 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
> index a522423..d5b4b2d 100644
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -35,6 +35,7 @@
>  #include <asm/p2m.h>
>  #include <asm/atomic.h>
>  #include <asm/event.h>
> +#include <asm/altp2m.h>
>  #include <xsm/xsm.h>
>  
>  #include "mm-locks.h"
> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd, unsigned long sgfn, shr_handle_t
>      /* We managed to free a domain page. */
>      atomic_dec(&nr_shared_mfns);
>      atomic_inc(&nr_saved_mfns);
> +
> +    if( altp2m_active(cd) )
> +    {
> +        p2m_access_t a;
> +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
> +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
> +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, PAGE_ORDER_4K,
> +                                    p2m_ram_shared, a);
> +    }
> +
>      ret = 0;
>      
>  err_out:
> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> index 3cb6868..1ac3018 100644
> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -846,7 +846,7 @@ out:
>      if ( is_epte_present(&old_entry) )
>          ept_free_entry(p2m, &old_entry, target);
>  
> -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
> +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
>          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt, p2ma);
>  
>      return rc;
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index b3fce1b..d2aebf7 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
>      /* Check host p2m if no valid entry in alternate */
>      if ( !mfn_valid(mfn) )
>      {
> -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
> -                              P2M_ALLOC | P2M_UNSHARE, &page_order, NULL);
> +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order, NULL);

Why are you getting rid of P2M_ALLOC here?  What happens if the hp2m
entry is populate-on-demand?

 -George


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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[Tamas K Lengyel]

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On Wed, Apr 27, 2016 at 9:01 AM, George Dunlap <george.dunlap@citrix.com>
wrote:

> On 21/04/16 18:10, Tamas K Lengyel wrote:
> > Don't propagate altp2m changes from ept_set_entry for memshare as
> memshare
> > already has the lock. We call altp2m propagate changes once memshare
> > successfully finishes. Also, allow the hostp2m entries to be of type
> > p2m_ram_shared.
> >
> > Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
>
> Sorry for the delay in reviewing -- trying to get my head back around
> the altp2m code.  On the whole looks reasonable, but one question...
>
> > ---
> > Cc: George Dunlap <george.dunlap@eu.citrix.com>
> > Cc: Keir Fraser <keir@xen.org>
> > Cc: Jan Beulich <jbeulich@suse.com>
> > Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> > Cc: Jun Nakajima <jun.nakajima@intel.com>
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > ---
> >  xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
> >  xen/arch/x86/mm/p2m-ept.c     |  2 +-
> >  xen/arch/x86/mm/p2m.c         |  7 +++----
> >  3 files changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/xen/arch/x86/mm/mem_sharing.c
> b/xen/arch/x86/mm/mem_sharing.c
> > index a522423..d5b4b2d 100644
> > --- a/xen/arch/x86/mm/mem_sharing.c
> > +++ b/xen/arch/x86/mm/mem_sharing.c
> > @@ -35,6 +35,7 @@
> >  #include <asm/p2m.h>
> >  #include <asm/atomic.h>
> >  #include <asm/event.h>
> > +#include <asm/altp2m.h>
> >  #include <xsm/xsm.h>
> >
> >  #include "mm-locks.h"
> > @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd,
> unsigned long sgfn, shr_handle_t
> >      /* We managed to free a domain page. */
> >      atomic_dec(&nr_shared_mfns);
> >      atomic_inc(&nr_saved_mfns);
> > +
> > +    if( altp2m_active(cd) )
> > +    {
> > +        p2m_access_t a;
> > +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
> > +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
> > +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, PAGE_ORDER_4K,
> > +                                    p2m_ram_shared, a);
> > +    }
> > +
> >      ret = 0;
> >
> >  err_out:
> > diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> > index 3cb6868..1ac3018 100644
> > --- a/xen/arch/x86/mm/p2m-ept.c
> > +++ b/xen/arch/x86/mm/p2m-ept.c
> > @@ -846,7 +846,7 @@ out:
> >      if ( is_epte_present(&old_entry) )
> >          ept_free_entry(p2m, &old_entry, target);
> >
> > -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
> > +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
> >          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt,
> p2ma);
> >
> >      return rc;
> > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> > index b3fce1b..d2aebf7 100644
> > --- a/xen/arch/x86/mm/p2m.c
> > +++ b/xen/arch/x86/mm/p2m.c
> > @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d,
> struct p2m_domain *hp2m,
> >      /* Check host p2m if no valid entry in alternate */
> >      if ( !mfn_valid(mfn) )
> >      {
> > -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
> > -                              P2M_ALLOC | P2M_UNSHARE, &page_order,
> NULL);
> > +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order,
> NULL);
>
> Why are you getting rid of P2M_ALLOC here?  What happens if the hp2m
> entry is populate-on-demand?
>

There is a check further down here that only allows p2m_ram_rw and
p2m_ram_shared. On the non-altp2m path mem_access doesn't request P2M_ALLOC
either (but doesn't check the type), so I would say mem_access is not
compatible with PoD.

Tamas

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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[George Dunlap]

On 27/04/16 16:18, Tamas K Lengyel wrote:
> On Wed, Apr 27, 2016 at 9:01 AM, George Dunlap <george.dunlap@citrix.com>
> wrote:
> 
>> On 21/04/16 18:10, Tamas K Lengyel wrote:
>>> Don't propagate altp2m changes from ept_set_entry for memshare as
>> memshare
>>> already has the lock. We call altp2m propagate changes once memshare
>>> successfully finishes. Also, allow the hostp2m entries to be of type
>>> p2m_ram_shared.
>>>
>>> Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
>>
>> Sorry for the delay in reviewing -- trying to get my head back around
>> the altp2m code.  On the whole looks reasonable, but one question...
>>
>>> ---
>>> Cc: George Dunlap <george.dunlap@eu.citrix.com>
>>> Cc: Keir Fraser <keir@xen.org>
>>> Cc: Jan Beulich <jbeulich@suse.com>
>>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
>>> Cc: Jun Nakajima <jun.nakajima@intel.com>
>>> Cc: Kevin Tian <kevin.tian@intel.com>
>>> ---
>>>  xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
>>>  xen/arch/x86/mm/p2m-ept.c     |  2 +-
>>>  xen/arch/x86/mm/p2m.c         |  7 +++----
>>>  3 files changed, 15 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/xen/arch/x86/mm/mem_sharing.c
>> b/xen/arch/x86/mm/mem_sharing.c
>>> index a522423..d5b4b2d 100644
>>> --- a/xen/arch/x86/mm/mem_sharing.c
>>> +++ b/xen/arch/x86/mm/mem_sharing.c
>>> @@ -35,6 +35,7 @@
>>>  #include <asm/p2m.h>
>>>  #include <asm/atomic.h>
>>>  #include <asm/event.h>
>>> +#include <asm/altp2m.h>
>>>  #include <xsm/xsm.h>
>>>
>>>  #include "mm-locks.h"
>>> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd,
>> unsigned long sgfn, shr_handle_t
>>>      /* We managed to free a domain page. */
>>>      atomic_dec(&nr_shared_mfns);
>>>      atomic_inc(&nr_saved_mfns);
>>> +
>>> +    if( altp2m_active(cd) )
>>> +    {
>>> +        p2m_access_t a;
>>> +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
>>> +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
>>> +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn, PAGE_ORDER_4K,
>>> +                                    p2m_ram_shared, a);
>>> +    }
>>> +
>>>      ret = 0;
>>>
>>>  err_out:
>>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
>>> index 3cb6868..1ac3018 100644
>>> --- a/xen/arch/x86/mm/p2m-ept.c
>>> +++ b/xen/arch/x86/mm/p2m-ept.c
>>> @@ -846,7 +846,7 @@ out:
>>>      if ( is_epte_present(&old_entry) )
>>>          ept_free_entry(p2m, &old_entry, target);
>>>
>>> -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
>>> +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
>>>          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt,
>> p2ma);
>>>
>>>      return rc;
>>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
>>> index b3fce1b..d2aebf7 100644
>>> --- a/xen/arch/x86/mm/p2m.c
>>> +++ b/xen/arch/x86/mm/p2m.c
>>> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d,
>> struct p2m_domain *hp2m,
>>>      /* Check host p2m if no valid entry in alternate */
>>>      if ( !mfn_valid(mfn) )
>>>      {
>>> -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
>>> -                              P2M_ALLOC | P2M_UNSHARE, &page_order,
>> NULL);
>>> +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order,
>> NULL);
>>
>> Why are you getting rid of P2M_ALLOC here?  What happens if the hp2m
>> entry is populate-on-demand?
>>
> 
> There is a check further down here that only allows p2m_ram_rw and
> p2m_ram_shared. 

So what P2M_ALLOC means is, "If this is entry is PoD, then please
populate it so I get a ram page."  So the only way you can get a
p2m_populate_on_demand type returned is if you remove this flag.  Leave
it and (assuming there's enough ram to go around), you'll always get
p2m_ram_rw.  :-)

> On the non-altp2m path mem_access doesn't request P2M_ALLOC
> either (but doesn't check the type), so I would say mem_access is not
> compatible with PoD.

Off the top of my head I can't see a reason why they couldn't co-exist
in principle, if you added P2M_ALLOC in a few key places.

 -George


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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[Tamas K Lengyel]

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On Wed, Apr 27, 2016 at 9:31 AM, George Dunlap <george.dunlap@citrix.com>
wrote:

> On 27/04/16 16:18, Tamas K Lengyel wrote:
> > On Wed, Apr 27, 2016 at 9:01 AM, George Dunlap <george.dunlap@citrix.com
> >
> > wrote:
> >
> >> On 21/04/16 18:10, Tamas K Lengyel wrote:
> >>> Don't propagate altp2m changes from ept_set_entry for memshare as
> >> memshare
> >>> already has the lock. We call altp2m propagate changes once memshare
> >>> successfully finishes. Also, allow the hostp2m entries to be of type
> >>> p2m_ram_shared.
> >>>
> >>> Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
> >>
> >> Sorry for the delay in reviewing -- trying to get my head back around
> >> the altp2m code.  On the whole looks reasonable, but one question...
> >>
> >>> ---
> >>> Cc: George Dunlap <george.dunlap@eu.citrix.com>
> >>> Cc: Keir Fraser <keir@xen.org>
> >>> Cc: Jan Beulich <jbeulich@suse.com>
> >>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> >>> Cc: Jun Nakajima <jun.nakajima@intel.com>
> >>> Cc: Kevin Tian <kevin.tian@intel.com>
> >>> ---
> >>>  xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
> >>>  xen/arch/x86/mm/p2m-ept.c     |  2 +-
> >>>  xen/arch/x86/mm/p2m.c         |  7 +++----
> >>>  3 files changed, 15 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/xen/arch/x86/mm/mem_sharing.c
> >> b/xen/arch/x86/mm/mem_sharing.c
> >>> index a522423..d5b4b2d 100644
> >>> --- a/xen/arch/x86/mm/mem_sharing.c
> >>> +++ b/xen/arch/x86/mm/mem_sharing.c
> >>> @@ -35,6 +35,7 @@
> >>>  #include <asm/p2m.h>
> >>>  #include <asm/atomic.h>
> >>>  #include <asm/event.h>
> >>> +#include <asm/altp2m.h>
> >>>  #include <xsm/xsm.h>
> >>>
> >>>  #include "mm-locks.h"
> >>> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd,
> >> unsigned long sgfn, shr_handle_t
> >>>      /* We managed to free a domain page. */
> >>>      atomic_dec(&nr_shared_mfns);
> >>>      atomic_inc(&nr_saved_mfns);
> >>> +
> >>> +    if( altp2m_active(cd) )
> >>> +    {
> >>> +        p2m_access_t a;
> >>> +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
> >>> +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
> >>> +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn,
> PAGE_ORDER_4K,
> >>> +                                    p2m_ram_shared, a);
> >>> +    }
> >>> +
> >>>      ret = 0;
> >>>
> >>>  err_out:
> >>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> >>> index 3cb6868..1ac3018 100644
> >>> --- a/xen/arch/x86/mm/p2m-ept.c
> >>> +++ b/xen/arch/x86/mm/p2m-ept.c
> >>> @@ -846,7 +846,7 @@ out:
> >>>      if ( is_epte_present(&old_entry) )
> >>>          ept_free_entry(p2m, &old_entry, target);
> >>>
> >>> -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
> >>> +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
> >>>          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt,
> >> p2ma);
> >>>
> >>>      return rc;
> >>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> >>> index b3fce1b..d2aebf7 100644
> >>> --- a/xen/arch/x86/mm/p2m.c
> >>> +++ b/xen/arch/x86/mm/p2m.c
> >>> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d,
> >> struct p2m_domain *hp2m,
> >>>      /* Check host p2m if no valid entry in alternate */
> >>>      if ( !mfn_valid(mfn) )
> >>>      {
> >>> -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
> >>> -                              P2M_ALLOC | P2M_UNSHARE, &page_order,
> >> NULL);
> >>> +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order,
> >> NULL);
> >>
> >> Why are you getting rid of P2M_ALLOC here?  What happens if the hp2m
> >> entry is populate-on-demand?
> >>
> >
> > There is a check further down here that only allows p2m_ram_rw and
> > p2m_ram_shared.
>
> So what P2M_ALLOC means is, "If this is entry is PoD, then please
> populate it so I get a ram page."  So the only way you can get a
> p2m_populate_on_demand type returned is if you remove this flag.  Leave
> it and (assuming there's enough ram to go around), you'll always get
> p2m_ram_rw.  :-)
>
> > On the non-altp2m path mem_access doesn't request P2M_ALLOC
> > either (but doesn't check the type), so I would say mem_access is not
> > compatible with PoD.
>
> Off the top of my head I can't see a reason why they couldn't co-exist
> in principle, if you added P2M_ALLOC in a few key places.
>

Sure, I just rather do that in a separate patch and for now have the
mem_access paths behaving the same way before doing that adjustment.

Tamas

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Re: [PATCH] altp2m: Allow the hostp2m to be shared

[George Dunlap]

On 27/04/16 16:37, Tamas K Lengyel wrote:
> On Wed, Apr 27, 2016 at 9:31 AM, George Dunlap <george.dunlap@citrix.com>
> wrote:
> 
>> On 27/04/16 16:18, Tamas K Lengyel wrote:
>>> On Wed, Apr 27, 2016 at 9:01 AM, George Dunlap <george.dunlap@citrix.com
>>>
>>> wrote:
>>>
>>>> On 21/04/16 18:10, Tamas K Lengyel wrote:
>>>>> Don't propagate altp2m changes from ept_set_entry for memshare as
>>>> memshare
>>>>> already has the lock. We call altp2m propagate changes once memshare
>>>>> successfully finishes. Also, allow the hostp2m entries to be of type
>>>>> p2m_ram_shared.
>>>>>
>>>>> Signed-off-by: Tamas K Lengyel <tamas@tklengyel.com>
>>>>
>>>> Sorry for the delay in reviewing -- trying to get my head back around
>>>> the altp2m code.  On the whole looks reasonable, but one question...
>>>>
>>>>> ---
>>>>> Cc: George Dunlap <george.dunlap@eu.citrix.com>
>>>>> Cc: Keir Fraser <keir@xen.org>
>>>>> Cc: Jan Beulich <jbeulich@suse.com>
>>>>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
>>>>> Cc: Jun Nakajima <jun.nakajima@intel.com>
>>>>> Cc: Kevin Tian <kevin.tian@intel.com>
>>>>> ---
>>>>>  xen/arch/x86/mm/mem_sharing.c | 11 +++++++++++
>>>>>  xen/arch/x86/mm/p2m-ept.c     |  2 +-
>>>>>  xen/arch/x86/mm/p2m.c         |  7 +++----
>>>>>  3 files changed, 15 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/xen/arch/x86/mm/mem_sharing.c
>>>> b/xen/arch/x86/mm/mem_sharing.c
>>>>> index a522423..d5b4b2d 100644
>>>>> --- a/xen/arch/x86/mm/mem_sharing.c
>>>>> +++ b/xen/arch/x86/mm/mem_sharing.c
>>>>> @@ -35,6 +35,7 @@
>>>>>  #include <asm/p2m.h>
>>>>>  #include <asm/atomic.h>
>>>>>  #include <asm/event.h>
>>>>> +#include <asm/altp2m.h>
>>>>>  #include <xsm/xsm.h>
>>>>>
>>>>>  #include "mm-locks.h"
>>>>> @@ -1026,6 +1027,16 @@ int mem_sharing_share_pages(struct domain *sd,
>>>> unsigned long sgfn, shr_handle_t
>>>>>      /* We managed to free a domain page. */
>>>>>      atomic_dec(&nr_shared_mfns);
>>>>>      atomic_inc(&nr_saved_mfns);
>>>>> +
>>>>> +    if( altp2m_active(cd) )
>>>>> +    {
>>>>> +        p2m_access_t a;
>>>>> +        struct p2m_domain *p2m = p2m_get_hostp2m(cd);
>>>>> +        p2m->get_entry(p2m, cgfn, NULL, &a, 0, NULL, NULL);
>>>>> +        p2m_altp2m_propagate_change(cd, _gfn(cgfn), smfn,
>> PAGE_ORDER_4K,
>>>>> +                                    p2m_ram_shared, a);
>>>>> +    }
>>>>> +
>>>>>      ret = 0;
>>>>>
>>>>>  err_out:
>>>>> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
>>>>> index 3cb6868..1ac3018 100644
>>>>> --- a/xen/arch/x86/mm/p2m-ept.c
>>>>> +++ b/xen/arch/x86/mm/p2m-ept.c
>>>>> @@ -846,7 +846,7 @@ out:
>>>>>      if ( is_epte_present(&old_entry) )
>>>>>          ept_free_entry(p2m, &old_entry, target);
>>>>>
>>>>> -    if ( rc == 0 && p2m_is_hostp2m(p2m) )
>>>>> +    if ( rc == 0 && p2m_is_hostp2m(p2m) && p2mt != p2m_ram_shared )
>>>>>          p2m_altp2m_propagate_change(d, _gfn(gfn), mfn, order, p2mt,
>>>> p2ma);
>>>>>
>>>>>      return rc;
>>>>> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
>>>>> index b3fce1b..d2aebf7 100644
>>>>> --- a/xen/arch/x86/mm/p2m.c
>>>>> +++ b/xen/arch/x86/mm/p2m.c
>>>>> @@ -1739,11 +1739,10 @@ int p2m_set_altp2m_mem_access(struct domain *d,
>>>> struct p2m_domain *hp2m,
>>>>>      /* Check host p2m if no valid entry in alternate */
>>>>>      if ( !mfn_valid(mfn) )
>>>>>      {
>>>>> -        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a,
>>>>> -                              P2M_ALLOC | P2M_UNSHARE, &page_order,
>>>> NULL);
>>>>> +        mfn = hp2m->get_entry(hp2m, gfn_l, &t, &old_a, 0, &page_order,
>>>> NULL);
>>>>
>>>> Why are you getting rid of P2M_ALLOC here?  What happens if the hp2m
>>>> entry is populate-on-demand?
>>>>
>>>
>>> There is a check further down here that only allows p2m_ram_rw and
>>> p2m_ram_shared.
>>
>> So what P2M_ALLOC means is, "If this is entry is PoD, then please
>> populate it so I get a ram page."  So the only way you can get a
>> p2m_populate_on_demand type returned is if you remove this flag.  Leave
>> it and (assuming there's enough ram to go around), you'll always get
>> p2m_ram_rw.  :-)
>>
>>> On the non-altp2m path mem_access doesn't request P2M_ALLOC
>>> either (but doesn't check the type), so I would say mem_access is not
>>> compatible with PoD.
>>
>> Off the top of my head I can't see a reason why they couldn't co-exist
>> in principle, if you added P2M_ALLOC in a few key places.
>>
> 
> Sure, I just rather do that in a separate patch and for now have the
> mem_access paths behaving the same way before doing that adjustment.

Ok, in that case please add a few sentences in the changelog addressing
the change.

Thanks,
 -George


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