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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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