From: Yang Weijiang <weijiang.yang@intel.com>
Enable guest shadow stack pointer(SSP) access interface with new uAPIs.
CET guest SSP is HW register which has corresponding VMCS field to save
/restore guest values when VM-{Exit,Entry} happens. KVM handles SSP as
a synthetic MSR for userspace access.
Use a translation helper to set up mapping for SSP synthetic index and
KVM-internal MSR index so that userspace doesn't need to take care of
KVM's management for synthetic MSRs and avoid conflicts.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Tested-by: Mathias Krause <minipli@grsecurity.net>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
---
arch/x86/include/uapi/asm/kvm.h | 3 +++
arch/x86/kvm/x86.c | 10 +++++++++-
arch/x86/kvm/x86.h | 10 ++++++++++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 969a63e73190..478d9b63a9db 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -432,6 +432,9 @@ struct kvm_xcrs {
#define KVM_X86_REG_SYNTHETIC_MSR(index) \
KVM_X86_REG_ENCODE(KVM_X86_REG_TYPE_SYNTHETIC_MSR, index)
+/* KVM synthetic MSR index staring from 0 */
+#define KVM_SYNTHETIC_GUEST_SSP 0
+
#define KVM_SYNC_X86_REGS (1UL << 0)
#define KVM_SYNC_X86_SREGS (1UL << 1)
#define KVM_SYNC_X86_EVENTS (1UL << 2)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 61e008be172d..a48e53b98c95 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5998,7 +5998,15 @@ struct kvm_x86_reg_id {
static int kvm_translate_synthetic_msr(struct kvm_x86_reg_id *reg)
{
- return -EINVAL;
+ switch (reg->index) {
+ case KVM_SYNTHETIC_GUEST_SSP:
+ reg->type = KVM_X86_REG_TYPE_MSR;
+ reg->index = MSR_KVM_INTERNAL_GUEST_SSP;
+ break;
+ default:
+ return -EINVAL;
+ }
+ return 0;
}
long kvm_arch_vcpu_ioctl(struct file *filp,
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index d90f1009ac10..0d11115dcd2a 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -101,6 +101,16 @@ do { \
#define KVM_SVM_DEFAULT_PLE_WINDOW_MAX USHRT_MAX
#define KVM_SVM_DEFAULT_PLE_WINDOW 3000
+/*
+ * KVM's internal, non-ABI indices for synthetic MSRs. The values themselves
+ * are arbitrary and have no meaning, the only requirement is that they don't
+ * conflict with "real" MSRs that KVM supports. Use values at the upper end
+ * of KVM's reserved paravirtual MSR range to minimize churn, i.e. these values
+ * will be usable until KVM exhausts its supply of paravirtual MSR indices.
+ */
+
+#define MSR_KVM_INTERNAL_GUEST_SSP 0x4b564dff
+
static inline unsigned int __grow_ple_window(unsigned int val,
unsigned int base, unsigned int modifier, unsigned int max)
{
--
2.47.3