Add KVM_SET_EXIT_MSRS ioctl to allow userspace to pass in a list of MSRs
that force an exit to userspace when rdmsr or wrmsr are used by the
guest.
KVM_SET_EXIT_MSRS will need to be called before any vCPUs are
created to protect the 'user_exit_msrs' list from being mutated while
vCPUs are running.
Add KVM_CAP_SET_MSR_EXITS to identify the feature exists.
Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 24 +++++++++++++++++++
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/x86.c | 41 +++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 2 ++
4 files changed, 69 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 91ce3e4b5b2e..e3cf1e971d0f 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1010,6 +1010,30 @@ such as migration.
:Parameters: struct kvm_vcpu_event (out)
:Returns: 0 on success, -1 on error
+4.32 KVM_SET_EXIT_MSRS
+------------------
+
+:Capability: KVM_CAP_SET_MSR_EXITS
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_msr_list (in)
+:Returns: 0 on success, -1 on error
+
+Sets the userspace MSR list which is used to track which MSRs KVM should send
+to userspace to be serviced when the guest executes rdmsr or wrmsr.
+
+This ioctl needs to be called before vCPUs are setup otherwise the list of MSRs
+will not be accepted and an EINVAL error will be returned. Also, if a list of
+MSRs has already been supplied, and this ioctl is called again an EEXIST error
+will be returned.
+
+::
+
+ struct kvm_msr_list {
+ __u32 nmsrs;
+ __u32 indices[0];
+};
+
X86:
^^^^
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1ee8468c913c..6c4c5b972395 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -976,6 +976,8 @@ struct kvm_arch {
struct kvm_pmu_event_filter *pmu_event_filter;
struct task_struct *nx_lpage_recovery_thread;
+
+ struct kvm_msr_list *user_exit_msrs;
};
struct kvm_vm_stat {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c46a709be532..e349d51d5d65 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3570,6 +3570,42 @@ static inline bool kvm_can_mwait_in_guest(void)
boot_cpu_has(X86_FEATURE_ARAT);
}
+static int kvm_vm_ioctl_set_exit_msrs(struct kvm *kvm,
+ struct kvm_msr_list __user *user_msr_list)
+{
+ struct kvm_msr_list *msr_list, hdr;
+ size_t indices_size;
+
+ if (kvm->arch.user_exit_msrs != NULL)
+ return -EEXIST;
+
+ if (kvm->created_vcpus)
+ return -EINVAL;
+
+ if (copy_from_user(&hdr, user_msr_list, sizeof(hdr)))
+ return -EFAULT;
+
+ if (hdr.nmsrs >= MAX_IO_MSRS)
+ return -E2BIG;
+
+ indices_size = sizeof(hdr.indices[0]) * hdr.nmsrs;
+ msr_list = kvzalloc(sizeof(struct kvm_msr_list) + indices_size,
+ GFP_KERNEL_ACCOUNT);
+ if (!msr_list)
+ return -ENOMEM;
+ msr_list->nmsrs = hdr.nmsrs;
+
+ if (copy_from_user(msr_list->indices, user_msr_list->indices,
+ indices_size)) {
+ kvfree(msr_list);
+ return -EFAULT;
+ }
+
+ kvm->arch.user_exit_msrs = msr_list;
+
+ return 0;
+}
+
int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
{
int r = 0;
@@ -3630,6 +3666,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_LAST_CPU:
case KVM_CAP_X86_USER_SPACE_MSR:
case KVM_CAP_X86_MSR_ALLOWLIST:
+ case KVM_CAP_SET_MSR_EXITS:
r = 1;
break;
case KVM_CAP_SYNC_REGS:
@@ -5532,6 +5569,10 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = 0;
break;
}
+ case KVM_SET_EXIT_MSRS: {
+ r = kvm_vm_ioctl_set_exit_msrs(kvm, argp);
+ break;
+ }
case KVM_MEMORY_ENCRYPT_OP: {
r = -ENOTTY;
if (kvm_x86_ops.mem_enc_op)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 374021dc4e61..7d47d518a5d4 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1046,6 +1046,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_S390_DIAG318 186
#define KVM_CAP_X86_USER_SPACE_MSR 187
#define KVM_CAP_X86_MSR_ALLOWLIST 188
+#define KVM_CAP_SET_MSR_EXITS 189
#ifdef KVM_CAP_IRQ_ROUTING
@@ -1386,6 +1387,7 @@ struct kvm_s390_ucas_mapping {
/* Available with KVM_CAP_PMU_EVENT_FILTER */
#define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct kvm_pmu_event_filter)
#define KVM_PPC_SVM_OFF _IO(KVMIO, 0xb3)
+#define KVM_SET_EXIT_MSRS _IOW(KVMIO, 0xb4, struct kvm_msr_list)
/* ioctl for vm fd */
#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)
--
2.28.0.220.ged08abb693-goog
