On 4/5/2017 10:41 PM, George Dunlap wrote:
On Sun, Apr 2, 2017 at 1:24 PM, Yu Zhang <yu.c.zh...@linux.intel.com> wrote:
After an ioreq server has unmapped, the remaining p2m_ioreq_server
entries need to be reset back to p2m_ram_rw. This patch does this
asynchronously with the current p2m_change_entry_type_global()
interface.
New field entry_count is introduced in struct p2m_domain, to record
the number of p2m_ioreq_server p2m page table entries. One nature of
these entries is that they only point to 4K sized page frames, because
all p2m_ioreq_server entries are originated from p2m_ram_rw ones in
p2m_change_type_one(). We do not need to worry about the counting for
2M/1G sized pages.
Assuming that all p2m_ioreq_server entries are *created* by
p2m_change_type_one() may valid, but can you assume that they are only
ever *removed* by p2m_change_type_one() (or recalculation)?
What happens, for instance, if a guest balloons out one of the ram
pages? I don't immediately see anything preventing a p2m_ioreq_server
page from being ballooned out, nor anything on the
decrease_reservation() path decreasing p2m->ioreq.entry_count. Or did
I miss something?
Other than that, only one minor comment...
Thanks for your thorough consideration, George. But I do not think we need to
worry about this:
If the emulation is in process, the balloon driver cannot get a
p2m_ioreq_server page - because
it is already allocated.
And even when emulation is finished, the balloon driver successfully get this
page, and triggers
decrease_reservation, the purpose is to remove the current mapping relation
between the gfn
and mfn in p2m. So IIUC, p2m_remove_page() will be triggered if everything is
goes fine, and then
p2m_set_entry(), which will trigger the recalc logic eventually, either in
ept_set_entry() or
p2m_pt_set_entry(). Then the entry_count will be updated in the recalc logic.
diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index a57b385..6ec950a 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -187,6 +187,15 @@ out:
*/
static int hap_enable_log_dirty(struct domain *d, bool_t log_global)
{
+ struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+ /*
+ * Refuse to turn on global log-dirty mode if
+ * there's outstanding p2m_ioreq_server pages.
Grammar nit: if *there are* outstanding pages.
Oh, right. Thanks
B.R.
Yu
-George
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
