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[J,1/2,v3] KVM: s390: Simplify SIGP Set Arch handling

Message ID 20220204151151.450613-2-frank.heimes@canonical.com
State New
Headers show
Series KVM: Improve SIGP architectural compliance (LP: 1959735) | expand

Commit Message

Frank Heimes Feb. 4, 2022, 3:11 p.m. UTC 
From: Eric Farman <farman@linux.ibm.com>

BugLink: https://bugs.launchpad.net/bugs/1959735

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

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;
 }