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Re: [RFC 2/6] roles: provide abstraction for the possible domain roles


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
  • Date: Thu, 3 Aug 2023 10:12:25 -0400
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 03 Aug 2023 14:12:49 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 8/2/23 03:51, Jan Beulich wrote:
On 01.08.2023 22:20, Daniel P. Smith wrote:
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -340,6 +340,14 @@ static int late_hwdom_init(struct domain *d)
      setup_io_bitmap(dom0);
  #endif
+ /*
+     * "dom0" may have been created under the unbounded role, demote it from
+     * that role, reducing it to the control domain role and any other roles it
+     * may have been given.
+     */
+    dom0->role &= ~(ROLE_UNBOUNDED_DOMAIN & ROLE_HARDWARE_DOMAIN);

This doesn't look to remove anything, when taking into account ...

Ugh, you are correct. It was meant to be a bitwise and of dom0-role with a mask that has every bit set except ROLE_UNBOUNDED_DOMAIN and ROLE_HARDWARE_DOMAIN. But being a bonehead, I bitwise and the two roles instead of or-ing them. I agree with your comment below, which will reduce to just masking a bitwise not of ROLE_HARDWARE_DOMAIN.

--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -467,8 +467,10 @@ struct domain
  #endif
      /* is node-affinity automatically computed? */
      bool             auto_node_affinity;
-    /* Is this guest fully privileged (aka dom0)? */
-    bool             is_privileged;
+#define ROLE_UNBOUNDED_DOMAIN  (1U<<0)
+#define ROLE_CONTROL_DOMAIN    (1U<<1)
+#define ROLE_HARDWARE_DOMAIN   (1U<<2)

... that each of the constants has just a single bit set. Seeing the
& there I was expecting something like

#define ROLE_UNBOUNDED_DOMAIN  (ROLE_CONTROL_DOMAIN | ROLE_HARDWARE_DOMAIN)

instead.

Agree, instead of consuming one the limited number of bits for a role that represents a domain having all roles, just or all the roles together. Then I can reclaim one of the bits of the flag field.

v/r,
dps




 


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