[PATCH RFC 01/11] KVM: x86: xen: Remove unneeded xen context from struct kvm_arch when !CONFIG_KVM_XEN

From: Vitaly Kuznetsov
Date: Tue Oct 10 2023 - 12:04:06 EST


Saving a few bytes of memory per KVM VM is certainly great but what's more
important is the ability to see where the code accesses Xen emulation
context while CONFIG_KVM_XEN is not enabled. Currently, kvm_cpu_get_extint()
is the only such place and it is harmless: kvm_xen_has_interrupt() always
returns '0' when !CONFIG_KVM_XEN.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 5 +++++
arch/x86/kvm/irq.c | 2 ++
2 files changed, 7 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 17715cb8731d..e5d4b8a44630 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1126,6 +1126,7 @@ struct msr_bitmap_range {
unsigned long *bitmap;
};

+#ifdef CONFIG_KVM_XEN
/* Xen emulation context */
struct kvm_xen {
struct mutex xen_lock;
@@ -1137,6 +1138,7 @@ struct kvm_xen {
struct idr evtchn_ports;
unsigned long poll_mask[BITS_TO_LONGS(KVM_MAX_VCPUS)];
};
+#endif

enum kvm_irqchip_mode {
KVM_IRQCHIP_NONE,
@@ -1338,7 +1340,10 @@ struct kvm_arch {
struct hlist_head mask_notifier_list;

struct kvm_hv hyperv;
+
+#ifdef CONFIG_KVM_XEN
struct kvm_xen xen;
+#endif

bool backwards_tsc_observed;
bool boot_vcpu_runs_old_kvmclock;
diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index b2c397dd2bc6..ad9ca8a60144 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -118,8 +118,10 @@ static int kvm_cpu_get_extint(struct kvm_vcpu *v)
if (!lapic_in_kernel(v))
return v->arch.interrupt.nr;

+#ifdef CONFIG_KVM_XEN
if (kvm_xen_has_interrupt(v))
return v->kvm->arch.xen.upcall_vector;
+#endif

if (irqchip_split(v->kvm)) {
int vector = v->arch.pending_external_vector;
--
2.41.0