Re: [Xen-devel] [PATCH V4] x86/ioreq_server: Make p2m_finish_type_change actually work

[George Dunlap]

On Fri, May 12, 2017 at 3:42 AM, Xiong Zhang  wrote:
> Commit 6d774a951696 ("x86/ioreq server: synchronously reset outstanding
> p2m_ioreq_server entries when an ioreq server unmaps") introduced
> p2m_finish_type_change(), which was meant to synchronously finish a
> previously initiated type change over a gpfn range.  It did this by
> calling get_entry(), checking if it was the appropriate type, and then
> calling set_entry().
>
> Unfortunately, a previous commit (1679e0df3df6 "x86/ioreq server:
> asynchronously reset outstanding p2m_ioreq_server entries") modified
> get_entry() to always return the new type after the type change, meaning
> that p2m_finish_type_change() never changed any entries.  Which means
> when an ioreq server was detached and then re-attached (as happens in
> XenGT on reboot) the re-attach failed.
>
> Fix this by using the existing p2m-specific recalculation logic instead
> of doing a read-check-write loop.
>
> Fix: 'commit 6d774a951696 ("x86/ioreq server: synchronously reset
>   outstanding p2m_ioreq_server entries when an ioreq server unmaps")'
>
> Signed-off-by: Xiong Zhang 
> Signed-off-by: Yu Zhang 
> Reviewed-by: George Dunlap 
> ---
> v1: Add ioreq_pre_recalc query flag to get the old p2m_type.(Jan)
> v2: Add p2m->recalc() hook to change gfn p2m_type. (George)
> v3: Make commit message clearer. (George)
> Keep the name of p2m-specific recal function unchanged. (Jan)
> v4: Move version info below S-o-B and handle return value of
> p2m->recalc. (Jan)

Sorry to be picky, but the handling of the return value introduces
another way the patch could be incorrect, so you should have dropped
my R-b.

I'll respond to v5.

 -George

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Re: [Xen-devel] [PATCH V4] x86/ioreq_server: Make p2m_finish_type_change actually work

[Julien Grall]

Hi,

On 11/05/17 12:12, Jan Beulich wrote:

On 12.05.17 at 04:42,  wrote:

Commit 6d774a951696 ("x86/ioreq server: synchronously reset outstanding
p2m_ioreq_server entries when an ioreq server unmaps") introduced
p2m_finish_type_change(), which was meant to synchronously finish a
previously initiated type change over a gpfn range.  It did this by
calling get_entry(), checking if it was the appropriate type, and then
calling set_entry().

Unfortunately, a previous commit (1679e0df3df6 "x86/ioreq server:
asynchronously reset outstanding p2m_ioreq_server entries") modified
get_entry() to always return the new type after the type change, meaning
that p2m_finish_type_change() never changed any entries.  Which means
when an ioreq server was detached and then re-attached (as happens in
XenGT on reboot) the re-attach failed.

Fix this by using the existing p2m-specific recalculation logic instead
of doing a read-check-write loop.

Fix: 'commit 6d774a951696 ("x86/ioreq server: synchronously reset
  outstanding p2m_ioreq_server entries when an ioreq server unmaps")'

Signed-off-by: Xiong Zhang 
Signed-off-by: Yu Zhang 
Reviewed-by: George Dunlap 


Reviewed-by: Jan Beulich 
albeit I'm not overly happy with ...


+int p2m_finish_type_change(struct domain *d,
+   gfn_t first_gfn, unsigned long max_nr)
 {
 struct p2m_domain *p2m = p2m_get_hostp2m(d);
-p2m_type_t t;
 unsigned long gfn = gfn_x(first_gfn);
 unsigned long last_gfn = gfn + max_nr - 1;
-
-ASSERT(ot != nt);
-ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
+int rc = 0;

 p2m_lock(p2m);

 last_gfn = min(last_gfn, p2m->max_mapped_pfn);
 while ( gfn <= last_gfn )
 {
-get_gfn_query_unlocked(d, gfn, );
-
-if ( t == ot )
-p2m_change_type_one(d, gfn, t, nt);
+rc = p2m->recalc(p2m, gfn);
+/*
+ * ept->recalc could return 0/1/-ENOMEM. pt->recalc could return
+ * 0/-ENOMEM/-ENOENT, -ENOENT isn't an error as we are looping
+ * gfn here.
+ */
+if ( rc == -ENOENT)


NIT: space missing before )


+rc = 0;
+else if ( rc < 0 )
+{
+gdprintk(XENLOG_ERR, "p2m->recalc failed! Dom%d gfn=%lx\n",
+ d->domain_id, gfn);


... a message being logged here.

Also I'm sure it was pointed out before that if this is meant for
4.9 (which I assume it is) you should have Cc-ed Julien (now
added).


Xiong Zhang, can you confirm this is meant for Xen 4.9?

Cheers,

--
Julien Grall

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Re: [Xen-devel] [PATCH V4] x86/ioreq_server: Make p2m_finish_type_change actually work

[Jan Beulich]

>>> On 12.05.17 at 04:42,  wrote:
> Commit 6d774a951696 ("x86/ioreq server: synchronously reset outstanding
> p2m_ioreq_server entries when an ioreq server unmaps") introduced
> p2m_finish_type_change(), which was meant to synchronously finish a
> previously initiated type change over a gpfn range.  It did this by
> calling get_entry(), checking if it was the appropriate type, and then
> calling set_entry().
> 
> Unfortunately, a previous commit (1679e0df3df6 "x86/ioreq server:
> asynchronously reset outstanding p2m_ioreq_server entries") modified
> get_entry() to always return the new type after the type change, meaning
> that p2m_finish_type_change() never changed any entries.  Which means
> when an ioreq server was detached and then re-attached (as happens in
> XenGT on reboot) the re-attach failed.
> 
> Fix this by using the existing p2m-specific recalculation logic instead
> of doing a read-check-write loop.
> 
> Fix: 'commit 6d774a951696 ("x86/ioreq server: synchronously reset
>   outstanding p2m_ioreq_server entries when an ioreq server unmaps")'
> 
> Signed-off-by: Xiong Zhang 
> Signed-off-by: Yu Zhang 
> Reviewed-by: George Dunlap 

Reviewed-by: Jan Beulich 
albeit I'm not overly happy with ...

> +int p2m_finish_type_change(struct domain *d,
> +   gfn_t first_gfn, unsigned long max_nr)
>  {
>  struct p2m_domain *p2m = p2m_get_hostp2m(d);
> -p2m_type_t t;
>  unsigned long gfn = gfn_x(first_gfn);
>  unsigned long last_gfn = gfn + max_nr - 1;
> -
> -ASSERT(ot != nt);
> -ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
> +int rc = 0;
>  
>  p2m_lock(p2m);
>  
>  last_gfn = min(last_gfn, p2m->max_mapped_pfn);
>  while ( gfn <= last_gfn )
>  {
> -get_gfn_query_unlocked(d, gfn, );
> -
> -if ( t == ot )
> -p2m_change_type_one(d, gfn, t, nt);
> +rc = p2m->recalc(p2m, gfn);
> +/* 
> + * ept->recalc could return 0/1/-ENOMEM. pt->recalc could return
> + * 0/-ENOMEM/-ENOENT, -ENOENT isn't an error as we are looping
> + * gfn here.
> + */
> +if ( rc == -ENOENT)
> +rc = 0;
> +else if ( rc < 0 )
> +{
> +gdprintk(XENLOG_ERR, "p2m->recalc failed! Dom%d gfn=%lx\n",
> + d->domain_id, gfn);

... a message being logged here.

Also I'm sure it was pointed out before that if this is meant for
4.9 (which I assume it is) you should have Cc-ed Julien (now
added).

Jan


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[Xen-devel] [PATCH V4] x86/ioreq_server: Make p2m_finish_type_change actually work

[Xiong Zhang]

Commit 6d774a951696 ("x86/ioreq server: synchronously reset outstanding
p2m_ioreq_server entries when an ioreq server unmaps") introduced
p2m_finish_type_change(), which was meant to synchronously finish a
previously initiated type change over a gpfn range.  It did this by
calling get_entry(), checking if it was the appropriate type, and then
calling set_entry().

Unfortunately, a previous commit (1679e0df3df6 "x86/ioreq server:
asynchronously reset outstanding p2m_ioreq_server entries") modified
get_entry() to always return the new type after the type change, meaning
that p2m_finish_type_change() never changed any entries.  Which means
when an ioreq server was detached and then re-attached (as happens in
XenGT on reboot) the re-attach failed.

Fix this by using the existing p2m-specific recalculation logic instead
of doing a read-check-write loop.

Fix: 'commit 6d774a951696 ("x86/ioreq server: synchronously reset
  outstanding p2m_ioreq_server entries when an ioreq server unmaps")'

Signed-off-by: Xiong Zhang 
Signed-off-by: Yu Zhang 
Reviewed-by: George Dunlap 
---
v1: Add ioreq_pre_recalc query flag to get the old p2m_type.(Jan)
v2: Add p2m->recalc() hook to change gfn p2m_type. (George)
v3: Make commit message clearer. (George)
Keep the name of p2m-specific recal function unchanged. (Jan)
v4: Move version info below S-o-B and handle return value of
p2m->recalc. (Jan)
---
 xen/arch/x86/hvm/dm.c |  5 +++--
 xen/arch/x86/mm/p2m-ept.c |  1 +
 xen/arch/x86/mm/p2m-pt.c  |  1 +
 xen/arch/x86/mm/p2m.c | 35 +++
 xen/include/asm-x86/p2m.h |  7 ---
 5 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index d72b7bd..99bf66a 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -412,8 +412,9 @@ static int dm_op(domid_t domid,
 first_gfn <= p2m->max_mapped_pfn )
 {
 /* Iterate p2m table for 256 gfns each time. */
-p2m_finish_type_change(d, _gfn(first_gfn), 256,
-   p2m_ioreq_server, p2m_ram_rw);
+rc = p2m_finish_type_change(d, _gfn(first_gfn), 256);
+if ( rc < 0 )
+break;
 
 first_gfn += 256;
 
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index f37a1f2..09efba7 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -1238,6 +1238,7 @@ int ept_p2m_init(struct p2m_domain *p2m)
 
 p2m->set_entry = ept_set_entry;
 p2m->get_entry = ept_get_entry;
+p2m->recalc = resolve_misconfig;
 p2m->change_entry_type_global = ept_change_entry_type_global;
 p2m->change_entry_type_range = ept_change_entry_type_range;
 p2m->memory_type_changed = ept_memory_type_changed;
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 5079b59..2eddeee 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -1153,6 +1153,7 @@ void p2m_pt_init(struct p2m_domain *p2m)
 {
 p2m->set_entry = p2m_pt_set_entry;
 p2m->get_entry = p2m_pt_get_entry;
+p2m->recalc = do_recalc;
 p2m->change_entry_type_global = p2m_pt_change_entry_type_global;
 p2m->change_entry_type_range = p2m_pt_change_entry_type_range;
 p2m->write_p2m_entry = paging_write_p2m_entry;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 1d57e5c..668c5a6 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1011,33 +1011,44 @@ void p2m_change_type_range(struct domain *d,
 p2m_unlock(p2m);
 }
 
-/* Synchronously modify the p2m type for a range of gfns from ot to nt. */
-void p2m_finish_type_change(struct domain *d,
-gfn_t first_gfn, unsigned long max_nr,
-p2m_type_t ot, p2m_type_t nt)
+/*
+ * Finish p2m type change for gfns which are marked as need_recalc in a range.
+ * Returns: 0/1 for success, negative for failure
+ */
+int p2m_finish_type_change(struct domain *d,
+   gfn_t first_gfn, unsigned long max_nr)
 {
 struct p2m_domain *p2m = p2m_get_hostp2m(d);
-p2m_type_t t;
 unsigned long gfn = gfn_x(first_gfn);
 unsigned long last_gfn = gfn + max_nr - 1;
-
-ASSERT(ot != nt);
-ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
+int rc = 0;
 
 p2m_lock(p2m);
 
 last_gfn = min(last_gfn, p2m->max_mapped_pfn);
 while ( gfn <= last_gfn )
 {
-get_gfn_query_unlocked(d, gfn, );
-
-if ( t == ot )
-p2m_change_type_one(d, gfn, t, nt);
+rc = p2m->recalc(p2m, gfn);
+/* 
+ * ept->recalc could return 0/1/-ENOMEM. pt->recalc could return
+ * 0/-ENOMEM/-ENOENT, -ENOENT isn't an error as we are looping
+ * gfn here.
+ */
+if ( rc == -ENOENT)
+rc = 0;
+else if ( rc < 0 )
+