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Re: [PATCH v1 1/2] domctl: Handle XEN_DOMCTL_getpageframeinfo3 without the domctl lock


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
  • Date: Thu, 11 Jun 2026 10:25:39 -0400
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  • Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • Delivery-date: Thu, 11 Jun 2026 14:25:55 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 6/11/26 10:23 AM, Roger Pau Monné wrote:
On Thu, Jun 11, 2026 at 09:11:15AM -0400, Daniel P. Smith wrote:
On 6/9/26 11:15 AM, Ross Lagerwall wrote:
It does not have side effects and is protected from concurrent changes
by the P2M read lock therefore skip taking the domctl lock.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
   xen/arch/x86/domctl.c | 4 ++++
   xen/common/domctl.c   | 1 +
   2 files changed, 5 insertions(+)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 83bf51e498df..0e9a2532887e 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -301,6 +301,10 @@ long arch_do_domctl(
           /* Games to allow this code block to handle a compat guest. */
           void __user *guest_handle = domctl->u.getpageframeinfo3.array.p;
+        ret = xsm_domctl(XSM_OTHER, d, domctl);
+        if ( ret )
+            break;
+
           if ( unlikely(num > 1024) ||
                unlikely(num != domctl->u.getpageframeinfo3.num) )
           {
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 3efa5b9d55b9..35144d95b808 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -555,6 +555,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
       case XEN_DOMCTL_gsi_permission:
       case XEN_DOMCTL_bind_pt_irq:
       case XEN_DOMCTL_unbind_pt_irq:
+    case XEN_DOMCTL_getpageframeinfo3:
           ret = arch_do_domctl(op, d, u_domctl);
           goto domctl_out_unlock_domonly;
I would respectfully ask to be mindful when XSM hooks are being manipulated
in a patch that a review from an XSM maintainer should be sought before
committing a patch. In this case case the change itself is good, though I
would have liked the opportunity to comment that the commit message should
have had some explanation on the xsm change.

I've already replied to 2/2, but would like to re-instate my apology
here so it doesn't seem like this went unnoticed:

Sorry, this was already picked up in a rush to get it into 4.22 and I
didn't realize it was missing an XSM maintainer Ack.  That's entirely
my fault, there was no intention to bypass or overrule your opinion.

No worries, thank you for the apologies.
.




 


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