[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v7 4/5] ix86/ioreq server: Asynchronously reset outstanding p2m_ioreq_server entries.





On 3/11/2017 12:03 AM, Jan Beulich wrote:
On 08.03.17 at 16:33, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -954,6 +954,26 @@ int p2m_change_type_one(struct domain *d, unsigned long 
gfn,
                           p2m->default_access)
           : -EBUSY;
+ if ( !rc )
+    {
+        switch ( nt )
+        {
+        case p2m_ram_rw:
+            if ( ot == p2m_ioreq_server )
+            {
+                p2m->ioreq.entry_count--;
+                ASSERT(p2m->ioreq.entry_count >= 0);
+            }
+            break;
+        case p2m_ioreq_server:
+            if ( ot == p2m_ram_rw )
+                p2m->ioreq.entry_count++;
I don't think the conditional is needed here. If anything it should be
an ASSERT() imo, as other transitions to p2m_ioreq_server should
not be allowed.

Thanks, Jan. I'll use ASSERT.

But there's a wider understanding issue I'm having here: What is
an "entry" here? Commonly I would assume this to refer to an
individual (4k) page, but it looks like you really mean table entry,
i.e. possibly representing a 2M or 1G page.

Well, it should be an entry pointing to a 4K page(only).
For p2m_ioreq_server, we shall not meet huge page. Because they are changed from p2m_ram_rw pages in set_mem_type() -> p2m_change_type_one(), which calls p2m_set_entry() with PAGE_ORDER_4K specified.


Thanks
Yu
Jan




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.