[PATCH] xen/domain: enable VCPUOP_register_runstate_phys_area hypercall

[PATCH] xen/domain: enable VCPUOP_register_runstate_phys_area hypercall

[torsten.oehlenschlager]

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ice@blossom ..............................................................................................................................................................................…/xen 🌸 enable-runstate-phys-area ?
❯ cat 0001-xen-domain-enable-VCPUOP_register_runstate_phys_area.patch
From 416992b30258d34b7cc7bc4f7875719f47618147 Mon Sep 17 00:00:00 2001
From: melanie <torsten.oehlenschlager@tutanota.de>
Date: Fri, 12 Dec 2025 20:55:50 +0000
Subject: [PATCH] xen/domain: enable VCPUOP_register_runstate_phys_area
hypercall

The XENFEAT_runstate_phys_area feature is unconditionally advertised to
guests via XENVER_get_features ( see xen/common/kernel.c ),  but the
corresponding VCPUOP_register_runstate_phys_area hypercall was disabled
with a placeholder check that always returned -ENOSYS!

Remove the dead code to enable the hypercall,  making the implementation
consistent with the advertised feature.

Signed-off-by: melanie <torsten.oehlenschlager@tutanota.de>
---
xen/common/domain.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 93c71bc766..3ae8d41cf2 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -2284,10 +2284,6 @@ long common_vcpu_op(int cmd, struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg)
     {
         struct vcpu_register_runstate_memory_area area;

-        rc = -ENOSYS;
-        if ( 0 /* TODO: Dom's XENFEAT_runstate_phys_area setting */ )
-            break;
-
         rc = -EFAULT;
         if ( copy_from_guest(&area.addr.p, arg, 1) )
             break;
--

-- 

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Re: [PATCH] xen/domain: enable VCPUOP_register_runstate_phys_area hypercall

[Jan Beulich]

On 12.12.2025 22:01, torsten.oehlenschlager@tutanota.de wrote:
> ice@blossom ..............................................................................................................................................................................…/xen 🌸 enable-runstate-phys-area ?
> ❯ cat 0001-xen-domain-enable-VCPUOP_register_runstate_phys_area.patch

I don't quite understand what this is.

> From 416992b30258d34b7cc7bc4f7875719f47618147 Mon Sep 17 00:00:00 2001
> From: melanie <torsten.oehlenschlager@tutanota.de>
> Date: Fri, 12 Dec 2025 20:55:50 +0000
> Subject: [PATCH] xen/domain: enable VCPUOP_register_runstate_phys_area
> hypercall
> 
> The XENFEAT_runstate_phys_area feature is unconditionally advertised to
> guests via XENVER_get_features ( see xen/common/kernel.c ),  but the
> corresponding VCPUOP_register_runstate_phys_area hypercall was disabled
> with a placeholder check that always returned -ENOSYS!

Well, no. The check you remove ...

> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -2284,10 +2284,6 @@ long common_vcpu_op(int cmd, struct vcpu *v, XEN_GUEST_HANDLE_PARAM(void) arg)
>      {
>          struct vcpu_register_runstate_memory_area area;
> 
> -        rc = -ENOSYS;
> -        if ( 0 /* TODO: Dom's XENFEAT_runstate_phys_area setting */ )
> -            break;

... is dead code, yes, but it certainly didn't cause the function to
return -ENOSYS. See commit 48a3fd14327f ("domain: expose newly introduced
hypercalls as XENFEAT"), which in a change like this the description surely
should have referenced.

Jan