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Message-Id: <2b2774154f7532c96a6f04d71c82a8bec7d9e80b.1646655860.git.houwenlong.hwl@antgroup.com> Date: Mon, 07 Mar 2022 20:26:33 +0800 From: "Hou Wenlong" <houwenlong.hwl@...group.com> To: kvm@...r.kernel.org Cc: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org Subject: [PATCH v2 1/2] 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 <houwenlong.hwl@...group.com> --- 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 a60b4d20b309..3497a35bd085 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3623,7 +3623,7 @@ 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; @@ -3640,7 +3640,7 @@ 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 39eded2426ff..29ac5a9679e5 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 cf17af4d6904..09c5677f4186 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1736,9 +1736,6 @@ 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: @@ -1820,9 +1817,6 @@ 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)) @@ -1859,6 +1853,20 @@ 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); @@ -1941,7 +1949,7 @@ 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); @@ -1966,7 +1974,7 @@ 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); @@ -7606,13 +7614,13 @@ 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)) { @@ -7623,13 +7631,13 @@ 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)) { @@ -7640,6 +7648,18 @@ 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); @@ -7773,6 +7793,8 @@ 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, -- 2.31.1
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