[PATCH 18/18] KVM: x86: hyper-v: Handle VSM hcalls in user-space
From: Nicolas Saenz Julienne <hidden>
Date: 2024-06-09 15:59:36
Also in:
kvm, linux-arch, linux-doc, linux-hyperv, lkml
Subsystem:
documentation, generic include/asm header files, kernel virtual machine (kvm), kernel virtual machine for x86 (kvm/x86), kvm x86 hyper-v (kvm/hyper-v), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Arnd Bergmann, Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Let user-space handle all hypercalls that fall under the AccessVsm partition privilege flag. That is: - HvCallModifyVtlProtectionMask - HvCallEnablePartitionVtl - HvCallEnableVpVtl - HvCallVtlCall - HvCallVtlReturn All these are VTL aware and as such need to be handled in user-space. Additionally, select KVM_GENERIC_MEMORY_ATTRIBUTES when CONFIG_KVM_HYPERV is enabled, as it's necessary in order to implement VTL memory protections. Signed-off-by: Nicolas Saenz Julienne <redacted> --- Documentation/virt/kvm/api.rst | 23 +++++++++++++++++++++++ arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/hyperv.c | 29 +++++++++++++++++++++++++---- include/asm-generic/hyperv-tlfs.h | 6 +++++- 4 files changed, 54 insertions(+), 5 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 6d3bc5092ea63..77af2ccf49a30 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst@@ -8969,3 +8969,26 @@ HvCallGetVpIndexFromApicId. Currently, it is only used in conjunction with HV_ACCESS_VSM, and immediately exits to userspace with KVM_EXIT_HYPERV_HCALL as the reason. Userspace is expected to complete the hypercall before resuming execution. + +10.4 HV_ACCESS_VSM +------------------ + +:Location: CPUID.40000003H:EBX[bit 16] + +This CPUID indicates that KVM supports HvCallModifyVtlProtectionMask, +HvCallEnablePartitionVtl, HvCallEnableVpVtl, HvCallVtlCall, and +HvCallVtlReturn. Additionally, as a prerequirsite to being able to implement +Hyper-V VSM, it also identifies the availability of HvTranslateVirtualAddress, +as well as the VTL-aware aspects of HvCallSendSyntheticClusterIpi and +HvCallSendSyntheticClusterIpiEx. + +All these hypercalls immediately exit with KVM_EXIT_HYPERV_HCALL as the reason. +Userspace is expected to complete the hypercall before resuming execution. +Note that both IPI hypercalls will only exit to userspace if the request is +VTL-aware, which will only happen if HV_ACCESS_VSM is exposed to the guest. + +Access restriction memory attributes (4.141) are available to simplify +HvCallModifyVtlProtectionMask's implementation. + +Ultimately this CPUID also indicates that KVM_MP_STATE_HV_INACTIVE_VTL is +available.
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index fec95a7702703..8d851fe3b8c25 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig@@ -157,6 +157,7 @@ config KVM_SMM config KVM_HYPERV bool "Support for Microsoft Hyper-V emulation" depends on KVM + select KVM_GENERIC_MEMORY_ATTRIBUTES default y help Provides KVM support for emulating Microsoft Hyper-V. This allows KVM
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index dd64f41dc835d..1158c59a92790 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c@@ -2388,7 +2388,12 @@ static void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result) } } -static int kvm_hv_hypercall_complete(struct kvm_vcpu *vcpu, u64 result) +static inline bool kvm_hv_is_vtl_call_return(u16 code) +{ + return code == HVCALL_VTL_CALL || code == HVCALL_VTL_RETURN; +} + +static int kvm_hv_hypercall_complete(struct kvm_vcpu *vcpu, u16 code, u64 result) { u32 tlb_lock_count = 0; int ret;
@@ -2400,9 +2405,12 @@ static int kvm_hv_hypercall_complete(struct kvm_vcpu *vcpu, u64 result) result = HV_STATUS_INVALID_HYPERCALL_INPUT; trace_kvm_hv_hypercall_done(result); - kvm_hv_hypercall_set_result(vcpu, result); ++vcpu->stat.hypercalls; + /* VTL call and return don't set a hcall result */ + if (!kvm_hv_is_vtl_call_return(code)) + kvm_hv_hypercall_set_result(vcpu, result); + ret = kvm_skip_emulated_instruction(vcpu); if (tlb_lock_count)
@@ -2459,7 +2467,7 @@ static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu) kvm_hv_write_xmm(vcpu->run->hyperv.u.hcall.xmm); } - return kvm_hv_hypercall_complete(vcpu, result); + return kvm_hv_hypercall_complete(vcpu, code, result); } static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
@@ -2513,6 +2521,7 @@ static bool is_xmm_fast_hypercall(struct kvm_hv_hcall *hc) case HVCALL_SEND_IPI_EX: case HVCALL_GET_VP_REGISTERS: case HVCALL_SET_VP_REGISTERS: + case HVCALL_MODIFY_VTL_PROTECTION_MASK: case HVCALL_TRANSLATE_VIRTUAL_ADDRESS: return true; }
@@ -2552,6 +2561,12 @@ static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code) */ return !kvm_hv_is_syndbg_enabled(hv_vcpu->vcpu) || hv_vcpu->cpuid_cache.features_ebx & HV_DEBUGGING; + case HVCALL_MODIFY_VTL_PROTECTION_MASK: + case HVCALL_ENABLE_PARTITION_VTL: + case HVCALL_ENABLE_VP_VTL: + case HVCALL_VTL_CALL: + case HVCALL_VTL_RETURN: + return hv_vcpu->cpuid_cache.features_ebx & HV_ACCESS_VSM; case HVCALL_GET_VP_REGISTERS: case HVCALL_SET_VP_REGISTERS: return hv_vcpu->cpuid_cache.features_ebx &
@@ -2744,6 +2759,11 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) break; } goto hypercall_userspace_exit; + case HVCALL_MODIFY_VTL_PROTECTION_MASK: + case HVCALL_ENABLE_PARTITION_VTL: + case HVCALL_ENABLE_VP_VTL: + case HVCALL_VTL_CALL: + case HVCALL_VTL_RETURN: case HVCALL_GET_VP_REGISTERS: case HVCALL_SET_VP_REGISTERS: case HVCALL_TRANSLATE_VIRTUAL_ADDRESS:
@@ -2765,7 +2785,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) } hypercall_complete: - return kvm_hv_hypercall_complete(vcpu, ret); + return kvm_hv_hypercall_complete(vcpu, hc.code, ret); hypercall_userspace_exit: vcpu->run->exit_reason = KVM_EXIT_HYPERV;
@@ -2921,6 +2941,7 @@ int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, ent->ebx |= HV_POST_MESSAGES; ent->ebx |= HV_SIGNAL_EVENTS; ent->ebx |= HV_ENABLE_EXTENDED_HYPERCALLS; + ent->ebx |= HV_ACCESS_VSM; ent->ebx |= HV_ACCESS_VP_REGISTERS; ent->ebx |= HV_START_VIRTUAL_PROCESSOR;
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index e24b88ec4ec00..6b12e5818292c 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h@@ -149,9 +149,13 @@ union hv_reference_tsc_msr { /* Declare the various hypercall operations. */ #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE 0x0002 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST 0x0003 -#define HVCALL_ENABLE_VP_VTL 0x000f #define HVCALL_NOTIFY_LONG_SPIN_WAIT 0x0008 #define HVCALL_SEND_IPI 0x000b +#define HVCALL_MODIFY_VTL_PROTECTION_MASK 0x000c +#define HVCALL_ENABLE_PARTITION_VTL 0x000d +#define HVCALL_ENABLE_VP_VTL 0x000f +#define HVCALL_VTL_CALL 0x0011 +#define HVCALL_VTL_RETURN 0x0012 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX 0x0013 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX 0x0014 #define HVCALL_SEND_IPI_EX 0x0015
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2.40.1