[Public]
> -----Original Message-----
> From: Jan Beulich <[email protected]>
> Sent: Thursday, October 30, 2025 9:35 PM
> To: Penny, Zheng <[email protected]>
> Cc: Huang, Ray <[email protected]>; [email protected]; Andrew
> Cooper <[email protected]>; Roger Pau Monné <[email protected]>;
> [email protected]
> Subject: Re: [PATCH v3 27/28] xen/domctl: make HVM_PARAM_IDENT_PT
> conditional upon CONFIG_MGMT_HYPERCALLS
>
> On 13.10.2025 12:15, Penny Zheng wrote:
> > Helper domctl_lock_{acquire,release} is domctl_lock, which
> > HVM_PARAM_IDENT_PT uses to ensure synchronization and hence being a
> toolstack-only operation.
> > So we shall make HVM_PARAM_IDENT_PT conditional upon
> > CONFIG_MGMT_HYPERCALLS, returning -EOPNOTSUPP when
> MGMT_HYPERCALLS=n.
> >
> > Suggested-by: Jan Beulich <[email protected]>
>
> I fear this isn't quite what I suggested. The param get/set are XSM_TARGET,
> i.e.
> can be used by DM as well. The particular one here shouldn't be used by a DM,
> but
> that's a different question. Similarly in principle the PVH Dom0 building
> code should
> be able to use this path; it doesn't right now in favor of some open- coding.
>
> What iirc I did suggest was that the serialization isn't needed when no
> domctl can
> be used to otherwise alter (relevant) guest state.
Ah, true, serialization isn't needed when MGMT_HYPERCALLS=n, as no domctl-op
could alter the guest state at the same time.
Then maybe adding IS_ENABLED() checking is enough:
```
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 5a50721bd0..4e1b3ee5f4 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4324,7 +4324,7 @@ static int hvm_set_param(struct domain *d, uint32_t
index, uint64_t value)
* the domctl_lock.
*/
rc = -ERESTART;
- if ( !domctl_lock_acquire() )
+ if ( IS_ENABLED(CONFIG_MGMT_HYPERCALLS) && !domctl_lock_acquire() )
break;
rc = 0;
@@ -4334,7 +4334,8 @@ static int hvm_set_param(struct domain *d, uint32_t
index, uint64_t value)
paging_update_cr3(v, false);
domain_unpause(d);
- domctl_lock_release();
+ if ( IS_ENABLED(CONFIG_MGMT_HYPERCALLS) )
+ domctl_lock_release();
break;
case HVM_PARAM_DM_DOMAIN:
/* The only value this should ever be set to is DOMID_SELF */
```
>
> Jan
