From: Yang Weijiang 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 Signed-off-by: Yang Weijiang Tested-by: Mathias Krause Tested-by: John Allen Tested-by: Rick Edgecombe Signed-off-by: Chao Gao --- Documentation/virt/kvm/api.rst | 7 +++++++ arch/x86/include/uapi/asm/kvm.h | 3 +++ arch/x86/kvm/x86.c | 10 +++++++++- arch/x86/kvm/x86.h | 10 ++++++++++ 4 files changed, 29 insertions(+), 1 deletion(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 28fc12b46eeb..2b999408a768 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -2911,6 +2911,13 @@ such as set vcpu counter or reset vcpu, and they have the following id bit patte x86 MSR registers have the following id bit patterns:: 0x2030 0002 +Following are the KVM-defined registers for x86: +======================= ========= ============================================= + Encoding Register Description +======================= ========= ============================================= + 0x2030 0003 0000 0000 SSP Shadow Stack Pointer +======================= ========= ============================================= + 4.69 KVM_GET_ONE_REG -------------------- diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 508b713ca52e..8cc79eca34b2 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -437,6 +437,9 @@ struct kvm_xcrs { #define KVM_X86_REG_KVM(index) \ KVM_X86_REG_ENCODE(KVM_X86_REG_TYPE_KVM, index) +/* KVM-defined registers starting from 0 */ +#define KVM_REG_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 691f8e68046f..a6036eab3852 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5999,7 +5999,15 @@ struct kvm_x86_reg_id { static int kvm_translate_kvm_reg(struct kvm_x86_reg_id *reg) { - return -EINVAL; + switch (reg->index) { + case KVM_REG_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 34afe43579bb..cf4f73a95825 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