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KVM: x86/xen: Consolidate checks on Xen vCPU ID for singleshot timer hypercalls

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Hoist the checks on the Xen vCPU ID when handling set_singleshot_timer and
stop_singleshot_timer hypercalls out of their individual if-statements,
so that both checks on the ID are in common code.  kvm_xen_hcall_vcpu_op()
is already doubly committed to handling only singleshot timer hypercalls,
and even if that were to change in the future, the function could simply
be renamed and turned into a helper specifically for timer hypercalls.

Opportunistically add a comment to explain why the check exists; the code
looks rather nonsensical without the knowledge that @vcpu_id is a common
param for all per-vCPU hypercalls.

No functional change intended.

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Link: https://patch.msgid.link/20260630225619.511632-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-06-30 15:56:12 -07:00
parent e4ffb0ceb9
commit 32d7943e51
1 changed files with 11 additions and 9 deletions
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20
arch/x86/kvm/xen.c
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@ -1614,12 +1614,18 @@ static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
if (!kvm_xen_timer_enabled(vcpu))
return false;
if (cmd == VCPUOP_set_singleshot_timer) {
if (vcpu->arch.xen.vcpu_id != vcpu_id) {
*r = -EINVAL;
return true;
}
/*
* Reject the hypercall if the guest is trying to start/stop the timer
* for a different vCPU. Xen per-vCPU hypercalls take a target vCPU as
* a common parameter, as all per-vCPU hypercalls *except* single-shot
* timer updates can be cross-vCPU.
*/
if (vcpu->arch.xen.vcpu_id != vcpu_id) {
*r = -EINVAL;
return true;
}
if (cmd == VCPUOP_set_singleshot_timer) {
/*
* The only difference for 32-bit compat is the 4 bytes of
* padding after the interesting part of the structure. So
@ -1644,10 +1650,6 @@ static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
kvm_xen_start_timer(vcpu, oneshot.timeout_abs_ns, false);
} else {
if (vcpu->arch.xen.vcpu_id != vcpu_id) {
*r = -EINVAL;
return true;
}
kvm_xen_stop_timer(vcpu);
}