[SRU][I][F][PATCH v2 1/2] KVM: s390: Simplify SIGP Set Arch handling

[frank.heimes at canonical.com]

From: Eric Farman <farman at linux.ibm.com>

BugLink: https://bugs.launchpad.net/bugs/1962578

The Principles of Operations describe the various reasons that
each individual SIGP orders might be rejected, and the status
bit that are set for each condition.

For example, for the Set Architecture order, it states:

  "If it is not true that all other CPUs in the configu-
   ration are in the stopped or check-stop state, ...
   bit 54 (incorrect state) ... is set to one."

However, it also states:

  "... if the CZAM facility is installed, ...
   bit 55 (invalid parameter) ... is set to one."

Since the Configuration-z/Architecture-Architectural Mode (CZAM)
facility is unconditionally presented, there is no need to examine
each VCPU to determine if it is started/stopped. It can simply be
rejected outright with the Invalid Parameter bit.

Fixes: b697e435aeee ("KVM: s390: Support Configuration z/Architecture Mode")
Signed-off-by: Eric Farman <farman at linux.ibm.com>
Reviewed-by: Thomas Huth <thuth at redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda at linux.ibm.com>
Reviewed-by: David Hildenbrand <david at redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger at de.ibm.com>
Link: https://lore.kernel.org/r/20211008203112.1979843-2-farman@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger at de.ibm.com>
(cherry picked from commit 8eeba194a32e0f50329354a696baaa2e3d9accc5)
Signed-off-by: Frank Heimes <frank.heimes at canonical.com>
---
 arch/s390/kvm/sigp.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
index 3dc921e853b6..8aaee2892ec3 100644
--- a/arch/s390/kvm/sigp.c
+++ b/arch/s390/kvm/sigp.c
@@ -151,22 +151,10 @@ static int __sigp_stop_and_store_status(struct kvm_vcpu *vcpu,
 static int __sigp_set_arch(struct kvm_vcpu *vcpu, u32 parameter,
 			   u64 *status_reg)
 {
-	unsigned int i;
-	struct kvm_vcpu *v;
-	bool all_stopped = true;
-
-	kvm_for_each_vcpu(i, v, vcpu->kvm) {
-		if (v == vcpu)
-			continue;
-		if (!is_vcpu_stopped(v))
-			all_stopped = false;
-	}
-
 	*status_reg &= 0xffffffff00000000UL;
 
 	/* Reject set arch order, with czam we're always in z/Arch mode. */
-	*status_reg |= (all_stopped ? SIGP_STATUS_INVALID_PARAMETER :
-					SIGP_STATUS_INCORRECT_STATE);
+	*status_reg |= SIGP_STATUS_INVALID_PARAMETER;
 	return SIGP_CC_STATUS_STORED;
 }
 
-- 
2.25.1