Patchwork [04/14] KVM: arm64/sve: sys_regs: Demote redundant vcpu_has_sve() checks to WARNs

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Submitter Dave Martin
Date April 12, 2019, 4:28 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/772001/
State New
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Dave Martin - April 12, 2019, 4:28 p.m.
Because of the logic in kvm_arm_sys_reg_{get,set}_reg() and
sve_id_visibility(), we should never call
{get,set}_id_aa64zfr0_el1() for a vcpu where !vcpu_has_sve(vcpu).

To avoid the code giving the impression that it is valid for these
functions to be called in this situation, and to help the compiler
make the right optimisation decisions, this patch adds WARN_ON()
for these cases.

Given the way the logic is spread out, this seems preferable to
dropping the checks altogether.

Suggested-by: Andrew Jones <>
Signed-off-by: Dave Martin <>
 arch/arm64/kvm/sys_regs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 09e9b06..7046c76 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1144,7 +1144,7 @@  static int get_id_aa64zfr0_el1(struct kvm_vcpu *vcpu,
 	u64 val;
-	if (!vcpu_has_sve(vcpu))
+	if (WARN_ON(!vcpu_has_sve(vcpu)))
 		return -ENOENT;
 	val = guest_id_aa64zfr0_el1(vcpu);
@@ -1159,7 +1159,7 @@  static int set_id_aa64zfr0_el1(struct kvm_vcpu *vcpu,
 	int err;
 	u64 val;
-	if (!vcpu_has_sve(vcpu))
+	if (WARN_ON(!vcpu_has_sve(vcpu)))
 		return -ENOENT;
 	err = reg_from_user(&val, uaddr, id);