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authorSean Christopherson <seanjc@google.com>2024-08-30 06:36:00 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2024-09-04 17:02:34 +0200
commit590b09b1d88e18ae57f89930a6f7b89795d2e9f3 (patch)
tree1944ce6818672f76c18c562ef7f9d52fb7787620
parentx86/reboot: Unconditionally define cpu_emergency_virt_cb typedef (diff)
downloadlinux-590b09b1d88e18ae57f89930a6f7b89795d2e9f3.tar.xz
linux-590b09b1d88e18ae57f89930a6f7b89795d2e9f3.zip
KVM: x86: Register "emergency disable" callbacks when virt is enabled
Register the "disable virtualization in an emergency" callback just before KVM enables virtualization in hardware, as there is no functional need to keep the callbacks registered while KVM happens to be loaded, but is inactive, i.e. if KVM hasn't enabled virtualization. Note, unregistering the callback every time the last VM is destroyed could have measurable latency due to the synchronize_rcu() needed to ensure all references to the callback are dropped before KVM is unloaded. But the latency should be a small fraction of the total latency of disabling virtualization across all CPUs, and userspace can set enable_virt_at_load to completely eliminate the runtime overhead. Add a pointer in kvm_x86_ops to allow vendor code to provide its callback. There is no reason to force vendor code to do the registration, and either way KVM would need a new kvm_x86_ops hook. Suggested-by: Kai Huang <kai.huang@intel.com> Reviewed-by: Chao Gao <chao.gao@intel.com> Reviewed-by: Kai Huang <kai.huang@intel.com> Acked-by: Kai Huang <kai.huang@intel.com> Tested-by: Farrah Chen <farrah.chen@intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-ID: <20240830043600.127750-11-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/include/asm/kvm_host.h3
-rw-r--r--arch/x86/kvm/svm/svm.c5
-rw-r--r--arch/x86/kvm/vmx/main.c2
-rw-r--r--arch/x86/kvm/vmx/vmx.c6
-rw-r--r--arch/x86/kvm/vmx/x86_ops.h1
-rw-r--r--arch/x86/kvm/x86.c10
6 files changed, 18 insertions, 9 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 704aeecfe2c9..52443ccda320 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -36,6 +36,7 @@
#include <asm/kvm_page_track.h>
#include <asm/kvm_vcpu_regs.h>
#include <asm/hyperv-tlfs.h>
+#include <asm/reboot.h>
#define __KVM_HAVE_ARCH_VCPU_DEBUGFS
@@ -1631,6 +1632,8 @@ struct kvm_x86_ops {
int (*enable_virtualization_cpu)(void);
void (*disable_virtualization_cpu)(void);
+ cpu_emergency_virt_cb *emergency_disable_virtualization_cpu;
+
void (*hardware_unsetup)(void);
bool (*has_emulated_msr)(struct kvm *kvm, u32 index);
void (*vcpu_after_set_cpuid)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index a9adbe10c12e..9a0506ef87df 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4982,6 +4982,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.hardware_unsetup = svm_hardware_unsetup,
.enable_virtualization_cpu = svm_enable_virtualization_cpu,
.disable_virtualization_cpu = svm_disable_virtualization_cpu,
+ .emergency_disable_virtualization_cpu = svm_emergency_disable_virtualization_cpu,
.has_emulated_msr = svm_has_emulated_msr,
.vcpu_create = svm_vcpu_create,
@@ -5410,8 +5411,6 @@ static struct kvm_x86_init_ops svm_init_ops __initdata = {
static void __svm_exit(void)
{
kvm_x86_vendor_exit();
-
- cpu_emergency_unregister_virt_callback(svm_emergency_disable_virtualization_cpu);
}
static int __init svm_init(void)
@@ -5427,8 +5426,6 @@ static int __init svm_init(void)
if (r)
return r;
- cpu_emergency_register_virt_callback(svm_emergency_disable_virtualization_cpu);
-
/*
* Common KVM initialization _must_ come last, after this, /dev/kvm is
* exposed to userspace!
diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 4a5bf92edccf..7e2e78a14257 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -25,6 +25,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
.enable_virtualization_cpu = vmx_enable_virtualization_cpu,
.disable_virtualization_cpu = vmx_disable_virtualization_cpu,
+ .emergency_disable_virtualization_cpu = vmx_emergency_disable_virtualization_cpu,
+
.has_emulated_msr = vmx_has_emulated_msr,
.vm_size = sizeof(struct kvm_vmx),
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index cf7d937bfd2c..89682832dded 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -755,7 +755,7 @@ fault:
return -EIO;
}
-static void vmx_emergency_disable_virtualization_cpu(void)
+void vmx_emergency_disable_virtualization_cpu(void)
{
int cpu = raw_smp_processor_id();
struct loaded_vmcs *v;
@@ -8584,8 +8584,6 @@ static void __vmx_exit(void)
{
allow_smaller_maxphyaddr = false;
- cpu_emergency_unregister_virt_callback(vmx_emergency_disable_virtualization_cpu);
-
vmx_cleanup_l1d_flush();
}
@@ -8632,8 +8630,6 @@ static int __init vmx_init(void)
pi_init_cpu(cpu);
}
- cpu_emergency_register_virt_callback(vmx_emergency_disable_virtualization_cpu);
-
vmx_check_vmcs12_offsets();
/*
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index 205692c43a8e..b6a7cfc6ae31 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -15,6 +15,7 @@ void vmx_hardware_unsetup(void);
int vmx_check_processor_compat(void);
int vmx_enable_virtualization_cpu(void);
void vmx_disable_virtualization_cpu(void);
+void vmx_emergency_disable_virtualization_cpu(void);
int vmx_vm_init(struct kvm *kvm);
void vmx_vm_destroy(struct kvm *kvm);
int vmx_vcpu_precreate(struct kvm *kvm);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 431358167fa8..f72e5d89e942 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12512,6 +12512,16 @@ void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
}
EXPORT_SYMBOL_GPL(kvm_vcpu_deliver_sipi_vector);
+void kvm_arch_enable_virtualization(void)
+{
+ cpu_emergency_register_virt_callback(kvm_x86_ops.emergency_disable_virtualization_cpu);
+}
+
+void kvm_arch_disable_virtualization(void)
+{
+ cpu_emergency_unregister_virt_callback(kvm_x86_ops.emergency_disable_virtualization_cpu);
+}
+
int kvm_arch_enable_virtualization_cpu(void)
{
struct kvm *kvm;