From ac8d6cad3c7b39633d5899dc2fa9abec7135e83e Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Mon, 7 Mar 2022 20:26:33 +0800 Subject: [PATCH] KVM: x86: Only do MSR filtering when access MSR by rdmsr/wrmsr If MSR access is rejected by MSR filtering, kvm_set_msr()/kvm_get_msr() would return KVM_MSR_RET_FILTERED, and the return value is only handled well for rdmsr/wrmsr. However, some instruction emulation and state transition also use kvm_set_msr()/kvm_get_msr() to do msr access but may trigger some unexpected results if MSR access is rejected, E.g. RDPID emulation would inject a #UD but RDPID wouldn't cause a exit when RDPID is supported in hardware and ENABLE_RDTSCP is set. And it would also cause failure when load MSR at nested entry/exit. Since msr filtering is based on MSR bitmap, it is better to only do MSR filtering for rdmsr/wrmsr. Signed-off-by: Hou Wenlong Message-Id: <2b2774154f7532c96a6f04d71c82a8bec7d9e80b.1646655860.git.houwenlong.hwl@antgroup.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 4 ++-- arch/x86/kvm/kvm_emulate.h | 2 ++ arch/x86/kvm/x86.c | 50 +++++++++++++++++++++++++++++++++------------- 3 files changed, 40 insertions(+), 16 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c9f87c0..be83c9c 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3625,7 +3625,7 @@ static int em_wrmsr(struct x86_emulate_ctxt *ctxt) msr_data = (u32)reg_read(ctxt, VCPU_REGS_RAX) | ((u64)reg_read(ctxt, VCPU_REGS_RDX) << 32); - r = ctxt->ops->set_msr(ctxt, msr_index, msr_data); + r = ctxt->ops->set_msr_with_filter(ctxt, msr_index, msr_data); if (r == X86EMUL_IO_NEEDED) return r; @@ -3642,7 +3642,7 @@ static int em_rdmsr(struct x86_emulate_ctxt *ctxt) u64 msr_data; int r; - r = ctxt->ops->get_msr(ctxt, msr_index, &msr_data); + r = ctxt->ops->get_msr_with_filter(ctxt, msr_index, &msr_data); if (r == X86EMUL_IO_NEEDED) return r; diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h index a2a7654..1cbd46c 100644 --- a/arch/x86/kvm/kvm_emulate.h +++ b/arch/x86/kvm/kvm_emulate.h @@ -210,6 +210,8 @@ struct x86_emulate_ops { int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value); u64 (*get_smbase)(struct x86_emulate_ctxt *ctxt); void (*set_smbase)(struct x86_emulate_ctxt *ctxt, u64 smbase); + int (*set_msr_with_filter)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 data); + int (*get_msr_with_filter)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata); int (*set_msr)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 data); int (*get_msr)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata); int (*check_pmc)(struct x86_emulate_ctxt *ctxt, u32 pmc); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 2c13112..bc63ba5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1748,9 +1748,6 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data, { struct msr_data msr; - if (!host_initiated && !kvm_msr_allowed(vcpu, index, KVM_MSR_FILTER_WRITE)) - return KVM_MSR_RET_FILTERED; - switch (index) { case MSR_FS_BASE: case MSR_GS_BASE: @@ -1832,9 +1829,6 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data, struct msr_data msr; int ret; - if (!host_initiated && !kvm_msr_allowed(vcpu, index, KVM_MSR_FILTER_READ)) - return KVM_MSR_RET_FILTERED; - switch (index) { case MSR_TSC_AUX: if (!kvm_is_supported_user_return_msr(MSR_TSC_AUX)) @@ -1871,6 +1865,20 @@ static int kvm_get_msr_ignored_check(struct kvm_vcpu *vcpu, return ret; } +static int kvm_get_msr_with_filter(struct kvm_vcpu *vcpu, u32 index, u64 *data) +{ + if (!kvm_msr_allowed(vcpu, index, KVM_MSR_FILTER_READ)) + return KVM_MSR_RET_FILTERED; + return kvm_get_msr_ignored_check(vcpu, index, data, false); +} + +static int kvm_set_msr_with_filter(struct kvm_vcpu *vcpu, u32 index, u64 data) +{ + if (!kvm_msr_allowed(vcpu, index, KVM_MSR_FILTER_WRITE)) + return KVM_MSR_RET_FILTERED; + return kvm_set_msr_ignored_check(vcpu, index, data, false); +} + int kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data) { return kvm_get_msr_ignored_check(vcpu, index, data, false); @@ -1953,7 +1961,7 @@ int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu) u64 data; int r; - r = kvm_get_msr(vcpu, ecx, &data); + r = kvm_get_msr_with_filter(vcpu, ecx, &data); if (!r) { trace_kvm_msr_read(ecx, data); @@ -1978,7 +1986,7 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu) u64 data = kvm_read_edx_eax(vcpu); int r; - r = kvm_set_msr(vcpu, ecx, data); + r = kvm_set_msr_with_filter(vcpu, ecx, data); if (!r) { trace_kvm_msr_write(ecx, data); @@ -7631,13 +7639,13 @@ static void emulator_set_segment(struct x86_emulate_ctxt *ctxt, u16 selector, return; } -static int emulator_get_msr(struct x86_emulate_ctxt *ctxt, - u32 msr_index, u64 *pdata) +static int emulator_get_msr_with_filter(struct x86_emulate_ctxt *ctxt, + u32 msr_index, u64 *pdata) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); int r; - r = kvm_get_msr(vcpu, msr_index, pdata); + r = kvm_get_msr_with_filter(vcpu, msr_index, pdata); if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_RDMSR, 0, complete_emulated_rdmsr, r)) { @@ -7648,13 +7656,13 @@ static int emulator_get_msr(struct x86_emulate_ctxt *ctxt, return r; } -static int emulator_set_msr(struct x86_emulate_ctxt *ctxt, - u32 msr_index, u64 data) +static int emulator_set_msr_with_filter(struct x86_emulate_ctxt *ctxt, + u32 msr_index, u64 data) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); int r; - r = kvm_set_msr(vcpu, msr_index, data); + r = kvm_set_msr_with_filter(vcpu, msr_index, data); if (r && kvm_msr_user_space(vcpu, msr_index, KVM_EXIT_X86_WRMSR, data, complete_emulated_msr_access, r)) { @@ -7665,6 +7673,18 @@ static int emulator_set_msr(struct x86_emulate_ctxt *ctxt, return r; } +static int emulator_get_msr(struct x86_emulate_ctxt *ctxt, + u32 msr_index, u64 *pdata) +{ + return kvm_get_msr(emul_to_vcpu(ctxt), msr_index, pdata); +} + +static int emulator_set_msr(struct x86_emulate_ctxt *ctxt, + u32 msr_index, u64 data) +{ + return kvm_set_msr(emul_to_vcpu(ctxt), msr_index, data); +} + static u64 emulator_get_smbase(struct x86_emulate_ctxt *ctxt) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); @@ -7803,6 +7823,8 @@ static const struct x86_emulate_ops emulate_ops = { .set_dr = emulator_set_dr, .get_smbase = emulator_get_smbase, .set_smbase = emulator_set_smbase, + .set_msr_with_filter = emulator_set_msr_with_filter, + .get_msr_with_filter = emulator_get_msr_with_filter, .set_msr = emulator_set_msr, .get_msr = emulator_get_msr, .check_pmc = emulator_check_pmc, -- 2.7.4