On 1/12/21 6:15 AM, Vitaly Kuznetsov wrote:
Wei Huang <wei.huang2@xxxxxxx> writes:From: Bandan Das <bsd@xxxxxxxxxx> While running VM related instructions (VMRUN/VMSAVE/VMLOAD), some AMD CPUs check EAX against reserved memory regions (e.g. SMM memory on host) before checking VMCB's instruction intercept. If EAX falls into such memory areas, #GP is triggered before VMEXIT. This causes problem under nested virtualization. To solve this problem, KVM needs to trap #GP and check the instructions triggering #GP. For VM execution instructions, KVM emulates these instructions; otherwise it re-injects #GP back to guest VMs. Signed-off-by: Bandan Das <bsd@xxxxxxxxxx> Co-developed-by: Wei Huang <wei.huang2@xxxxxxx> Signed-off-by: Wei Huang <wei.huang2@xxxxxxx> --- arch/x86/include/asm/kvm_host.h | 8 +- arch/x86/kvm/mmu.h | 1 + arch/x86/kvm/mmu/mmu.c | 7 ++ arch/x86/kvm/svm/svm.c | 157 +++++++++++++++++++------------- arch/x86/kvm/svm/svm.h | 8 ++ arch/x86/kvm/vmx/vmx.c | 2 +- arch/x86/kvm/x86.c | 37 +++++++- 7 files changed, 146 insertions(+), 74 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3d6616f6f6ef..0ddc309f5a14 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1450,10 +1450,12 @@ extern u64 kvm_mce_cap_supported; * due to an intercepted #UD (see EMULTYPE_TRAP_UD). * Used to test the full emulator from userspace. * - * EMULTYPE_VMWARE_GP - Set when emulating an intercepted #GP for VMware + * EMULTYPE_PARAVIRT_GP - Set when emulating an intercepted #GP for VMware * backdoor emulation, which is opt in via module param. * VMware backoor emulation handles select instructions - * and reinjects the #GP for all other cases. + * and reinjects #GP for all other cases. This also + * handles other cases where #GP condition needs to be + * handled and emulated appropriately * * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which * case the CR2/GPA value pass on the stack is valid. @@ -1463,7 +1465,7 @@ extern u64 kvm_mce_cap_supported; #define EMULTYPE_SKIP (1 << 2) #define EMULTYPE_ALLOW_RETRY_PF (1 << 3) #define EMULTYPE_TRAP_UD_FORCED (1 << 4) -#define EMULTYPE_VMWARE_GP (1 << 5) +#define EMULTYPE_PARAVIRT_GP (1 << 5) #define EMULTYPE_PF (1 << 6)int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 581925e476d6..1a2fff4e7140 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -219,5 +219,6 @@ int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);int kvm_mmu_post_init_vm(struct kvm *kvm);void kvm_mmu_pre_destroy_vm(struct kvm *kvm); +bool kvm_is_host_reserved_region(u64 gpa);Just a suggestion: "kvm_gpa_in_host_reserved()" maybe?
Will do in v2.
#endifdiff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 6d16481aa29d..c5c4aaf01a1a 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -50,6 +50,7 @@ #include <asm/io.h> #include <asm/vmx.h> #include <asm/kvm_page_track.h> +#include <asm/e820/api.h> #include "trace.h"extern bool itlb_multihit_kvm_mitigation;@@ -5675,6 +5676,12 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm, } EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);+bool kvm_is_host_reserved_region(u64 gpa)+{ + return e820__mbapped_raw_any(gpa-1, gpa+1, E820_TYPE_RESERVED); +}While _e820__mapped_any()'s doc says '.. checks if any part of the range <start,end> is mapped ..' it seems to me that the real check is [start, end) so we should use 'gpa' instead of 'gpa-1', no?
I think you are right. The statement of "entry->addr >= end || entry->addr + entry->size <= start" shows the checking is against the area of [start, end).
+EXPORT_SYMBOL_GPL(kvm_is_host_reserved_region); + void kvm_mmu_zap_all(struct kvm *kvm) { struct kvm_mmu_page *sp, *node; diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 7ef171790d02..74620d32aa82 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -288,6 +288,7 @@ int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer) if (!(efer & EFER_SVME)) { svm_leave_nested(svm); svm_set_gif(svm, true); + clr_exception_intercept(svm, GP_VECTOR);/** Free the nested guest state, unless we are in SMM. @@ -309,6 +310,10 @@ int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)svm->vmcb->save.efer = efer | EFER_SVME;vmcb_mark_dirty(svm->vmcb, VMCB_CR); + /* Enable GP interception for SVM instructions if needed */ + if (efer & EFER_SVME) + set_exception_intercept(svm, GP_VECTOR); + return 0; }@@ -1957,22 +1962,104 @@ static int ac_interception(struct vcpu_svm *svm)return 1; }+static int vmload_interception(struct vcpu_svm *svm)+{ + struct vmcb *nested_vmcb; + struct kvm_host_map map; + int ret; + + if (nested_svm_check_permissions(svm)) + return 1; + + ret = kvm_vcpu_map(&svm->vcpu, gpa_to_gfn(svm->vmcb->save.rax), &map); + if (ret) { + if (ret == -EINVAL) + kvm_inject_gp(&svm->vcpu, 0); + return 1; + } + + nested_vmcb = map.hva; + + ret = kvm_skip_emulated_instruction(&svm->vcpu); + + nested_svm_vmloadsave(nested_vmcb, svm->vmcb); + kvm_vcpu_unmap(&svm->vcpu, &map, true); + + return ret; +} + +static int vmsave_interception(struct vcpu_svm *svm) +{ + struct vmcb *nested_vmcb; + struct kvm_host_map map; + int ret; + + if (nested_svm_check_permissions(svm)) + return 1; + + ret = kvm_vcpu_map(&svm->vcpu, gpa_to_gfn(svm->vmcb->save.rax), &map); + if (ret) { + if (ret == -EINVAL) + kvm_inject_gp(&svm->vcpu, 0); + return 1; + } + + nested_vmcb = map.hva; + + ret = kvm_skip_emulated_instruction(&svm->vcpu); + + nested_svm_vmloadsave(svm->vmcb, nested_vmcb); + kvm_vcpu_unmap(&svm->vcpu, &map, true); + + return ret; +} + +static int vmrun_interception(struct vcpu_svm *svm) +{ + if (nested_svm_check_permissions(svm)) + return 1; + + return nested_svm_vmrun(svm); +} + +/* Emulate SVM VM execution instructions */ +static int svm_emulate_vm_instr(struct kvm_vcpu *vcpu, u8 modrm) +{ + struct vcpu_svm *svm = to_svm(vcpu); + + switch (modrm) { + case 0xd8: /* VMRUN */ + return vmrun_interception(svm); + case 0xda: /* VMLOAD */ + return vmload_interception(svm); + case 0xdb: /* VMSAVE */ + return vmsave_interception(svm); + default: + /* inject a #GP for all other cases */ + kvm_queue_exception_e(vcpu, GP_VECTOR, 0); + return 1; + } +} + static int gp_interception(struct vcpu_svm *svm) { struct kvm_vcpu *vcpu = &svm->vcpu; u32 error_code = svm->vmcb->control.exit_info_1; - - WARN_ON_ONCE(!enable_vmware_backdoor); + int rc;/*- * VMware backdoor emulation on #GP interception only handles IN{S}, - * OUT{S}, and RDPMC, none of which generate a non-zero error code. + * Only VMware backdoor and SVM VME errata are handled. Neither of + * them has non-zero error codes. */ if (error_code) { kvm_queue_exception_e(vcpu, GP_VECTOR, error_code); return 1; } - return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP); + + rc = kvm_emulate_instruction(vcpu, EMULTYPE_PARAVIRT_GP); + if (rc > 1) + rc = svm_emulate_vm_instr(vcpu, rc); + return rc; }static bool is_erratum_383(void)@@ -2113,66 +2200,6 @@ static int vmmcall_interception(struct vcpu_svm *svm) return kvm_emulate_hypercall(&svm->vcpu); }-static int vmload_interception(struct vcpu_svm *svm)-{ - struct vmcb *nested_vmcb; - struct kvm_host_map map; - int ret; - - if (nested_svm_check_permissions(svm)) - return 1; - - ret = kvm_vcpu_map(&svm->vcpu, gpa_to_gfn(svm->vmcb->save.rax), &map); - if (ret) { - if (ret == -EINVAL) - kvm_inject_gp(&svm->vcpu, 0); - return 1; - } - - nested_vmcb = map.hva; - - ret = kvm_skip_emulated_instruction(&svm->vcpu); - - nested_svm_vmloadsave(nested_vmcb, svm->vmcb); - kvm_vcpu_unmap(&svm->vcpu, &map, true); - - return ret; -} - -static int vmsave_interception(struct vcpu_svm *svm) -{ - struct vmcb *nested_vmcb; - struct kvm_host_map map; - int ret; - - if (nested_svm_check_permissions(svm)) - return 1; - - ret = kvm_vcpu_map(&svm->vcpu, gpa_to_gfn(svm->vmcb->save.rax), &map); - if (ret) { - if (ret == -EINVAL) - kvm_inject_gp(&svm->vcpu, 0); - return 1; - } - - nested_vmcb = map.hva; - - ret = kvm_skip_emulated_instruction(&svm->vcpu); - - nested_svm_vmloadsave(svm->vmcb, nested_vmcb); - kvm_vcpu_unmap(&svm->vcpu, &map, true); - - return ret; -} - -static int vmrun_interception(struct vcpu_svm *svm) -{ - if (nested_svm_check_permissions(svm)) - return 1; - - return nested_svm_vmrun(svm); -} -Maybe if you'd do it the other way around and put gp_interception() after vm{load,save,run}_interception(), the diff (and code churn) would've been smaller?
Agreed.
void svm_set_gif(struct vcpu_svm *svm, bool value) { if (value) { diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 0fe874ae5498..d5dffcf59afa 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -350,6 +350,14 @@ static inline void clr_exception_intercept(struct vcpu_svm *svm, u32 bit) recalc_intercepts(svm); }+static inline bool is_exception_intercept(struct vcpu_svm *svm, u32 bit)+{ + struct vmcb *vmcb = get_host_vmcb(svm); + + WARN_ON_ONCE(bit >= 32); + return vmcb_is_intercept(&vmcb->control, INTERCEPT_EXCEPTION_OFFSET + bit); +} + static inline void svm_set_intercept(struct vcpu_svm *svm, int bit) { struct vmcb *vmcb = get_host_vmcb(svm); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 2af05d3b0590..5fac2f7cba24 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4774,7 +4774,7 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) kvm_queue_exception_e(vcpu, GP_VECTOR, error_code); return 1; } - return kvm_emulate_instruction(vcpu, EMULTYPE_VMWARE_GP); + return kvm_emulate_instruction(vcpu, EMULTYPE_PARAVIRT_GP); }/*diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9a8969a6dd06..c3662fc3b1bc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7014,7 +7014,7 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) ++vcpu->stat.insn_emulation_fail; trace_kvm_emulate_insn_failed(vcpu);- if (emulation_type & EMULTYPE_VMWARE_GP) {+ if (emulation_type & EMULTYPE_PARAVIRT_GP) { kvm_queue_exception_e(vcpu, GP_VECTOR, 0); return 1; } @@ -7267,6 +7267,28 @@ static bool kvm_vcpu_check_breakpoint(struct kvm_vcpu *vcpu, int *r) return false; }+static int is_vm_instr_opcode(struct x86_emulate_ctxt *ctxt)Nit: it seems we either return '0' or 'ctxt->modrm' which is 'u8', so 'u8' instead of 'int' maybe?
Agreed. Also Paolo has some comments around this area as well. We will take these comments into consideration in v2.
+{ + unsigned long rax; + + if (ctxt->b != 0x1) + return 0; + + switch (ctxt->modrm) { + case 0xd8: /* VMRUN */ + case 0xda: /* VMLOAD */ + case 0xdb: /* VMSAVE */ + rax = kvm_register_read(emul_to_vcpu(ctxt), VCPU_REGS_RAX); + if (!kvm_is_host_reserved_region(rax)) + return 0; + break; + default: + return 0; + } + + return ctxt->modrm; +} + static bool is_vmware_backdoor_opcode(struct x86_emulate_ctxt *ctxt) { switch (ctxt->opcode_len) { @@ -7305,6 +7327,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt; bool writeback = true; bool write_fault_to_spt; + int vminstr;if (unlikely(!kvm_x86_ops.can_emulate_instruction(vcpu, insn, insn_len)))return 1; @@ -7367,10 +7390,14 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, } }- if ((emulation_type & EMULTYPE_VMWARE_GP) &&- !is_vmware_backdoor_opcode(ctxt)) { - kvm_queue_exception_e(vcpu, GP_VECTOR, 0); - return 1; + if (emulation_type & EMULTYPE_PARAVIRT_GP) { + vminstr = is_vm_instr_opcode(ctxt); + if (!vminstr && !is_vmware_backdoor_opcode(ctxt)) { + kvm_queue_exception_e(vcpu, GP_VECTOR, 0); + return 1; + } + if (vminstr) + return vminstr; }/*
