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Message-Id: <20210226115744.170536-1-pbonzini@redhat.com>
Date: Fri, 26 Feb 2021 06:57:44 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Christoph Hellwig <hch@....de>, David Woodhouse <dwmw@...zon.co.uk>
Subject: [PATCH v2] KVM: x86: allow compiling out the Xen hypercall interface
The Xen hypercall interface adds to the attack surface of the hypervisor
and will be used quite rarely. Allow compiling it out.
Suggested-by: Christoph Hellwig <hch@....de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
v1->v2: do not use stubs for the ioctls, cull KVM_CAP_XEN_HVM too
arch/x86/kvm/Kconfig | 9 +++++++++
arch/x86/kvm/Makefile | 3 ++-
arch/x86/kvm/x86.c | 8 ++++++++
arch/x86/kvm/xen.h | 24 +++++++++++++++++++++++-
4 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 7ac592664c52..bdda1a386293 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -103,6 +103,15 @@ config KVM_AMD_SEV
Provides support for launching Encrypted VMs (SEV) and Encrypted VMs
with Encrypted State (SEV-ES) on AMD processors.
+config KVM_XEN
+ bool "Support for Xen hypercall interface"
+ depends on KVM && IA32_FEAT_CTL
+ help
+ Provides KVM support for the hosting Xen HVM guests and
+ passing Xen hypercalls to userspace.
+
+ If in doubt, say "N".
+
config KVM_MMU_AUDIT
bool "Audit KVM MMU"
depends on KVM && TRACEPOINTS
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index aeab168c5711..1b4766fe1de2 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -14,11 +14,12 @@ kvm-y += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o \
$(KVM)/dirty_ring.o
kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
-kvm-y += x86.o emulate.o i8259.o irq.o lapic.o xen.o \
+kvm-y += x86.o emulate.o i8259.o irq.o lapic.o \
i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
hyperv.o debugfs.o mmu/mmu.o mmu/page_track.o \
mmu/spte.o
kvm-$(CONFIG_X86_64) += mmu/tdp_iter.o mmu/tdp_mmu.o
+kvm-$(CONFIG_KVM_XEN) += xen.o
kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
vmx/evmcs.o vmx/nested.o vmx/posted_intr.o
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bfc928495bd4..4a5ce57b0bb2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3755,11 +3755,13 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
r = 1;
break;
+#ifdef CONFIG_KVM_XEN
case KVM_CAP_XEN_HVM:
r = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
KVM_XEN_HVM_CONFIG_SHARED_INFO;
break;
+#endif
case KVM_CAP_SYNC_REGS:
r = KVM_SYNC_X86_VALID_FIELDS;
break;
@@ -5012,6 +5014,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
case KVM_GET_SUPPORTED_HV_CPUID:
r = kvm_ioctl_get_supported_hv_cpuid(vcpu, argp);
break;
+#ifdef CONFIG_KVM_XEN
case KVM_XEN_VCPU_GET_ATTR: {
struct kvm_xen_vcpu_attr xva;
@@ -5032,6 +5035,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = kvm_xen_vcpu_set_attr(vcpu, &xva);
break;
}
+#endif
default:
r = -EINVAL;
}
@@ -5653,6 +5657,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
kvm->arch.bsp_vcpu_id = arg;
mutex_unlock(&kvm->lock);
break;
+#ifdef CONFIG_KVM_XEN
case KVM_XEN_HVM_CONFIG: {
struct kvm_xen_hvm_config xhc;
r = -EFAULT;
@@ -5681,6 +5686,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = kvm_xen_hvm_set_attr(kvm, &xha);
break;
}
+#endif
case KVM_SET_CLOCK: {
struct kvm_clock_data user_ns;
u64 now_ns;
@@ -8039,8 +8045,10 @@ void kvm_arch_exit(void)
kvm_mmu_module_exit();
free_percpu(user_return_msrs);
kmem_cache_destroy(x86_fpu_cache);
+#ifdef CONFIG_KVM_XEN
static_key_deferred_flush(&kvm_xen_enabled);
WARN_ON(static_branch_unlikely(&kvm_xen_enabled.key));
+#endif
}
static int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index b66a921776f4..87eaf2be9549 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -9,6 +9,7 @@
#ifndef __ARCH_X86_KVM_XEN_H__
#define __ARCH_X86_KVM_XEN_H__
+#ifdef CONFIG_KVM_XEN
#include <linux/jump_label_ratelimit.h>
extern struct static_key_false_deferred kvm_xen_enabled;
@@ -18,7 +19,6 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data);
int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data);
-int kvm_xen_hypercall(struct kvm_vcpu *vcpu);
int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data);
int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc);
void kvm_xen_destroy_vm(struct kvm *kvm);
@@ -38,6 +38,28 @@ static inline int kvm_xen_has_interrupt(struct kvm_vcpu *vcpu)
return 0;
}
+#else
+static inline int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)
+{
+ return 1;
+}
+
+static inline void kvm_xen_destroy_vm(struct kvm *kvm)
+{
+}
+
+static inline bool kvm_xen_hypercall_enabled(struct kvm *kvm)
+{
+ return false;
+}
+
+static inline int kvm_xen_has_interrupt(struct kvm_vcpu *vcpu)
+{
+ return 0;
+}
+#endif
+
+int kvm_xen_hypercall(struct kvm_vcpu *vcpu);
/* 32-bit compatibility definitions, also used natively in 32-bit build */
#include <asm/pvclock-abi.h>
--
2.26.2
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