diff mbox series

[v2,5/8] KVM: x86: Ensure the MSR bitmap never clears userspace tracked MSRs

Message ID 20200810201134.2031613-6-aaronlewis@google.com (mailing list archive)
State New, archived
Headers show
Series Allow userspace to manage MSRs | expand

Commit Message

Aaron Lewis Aug. 10, 2020, 8:11 p.m. UTC 
SDM volume 3: 24.6.9 "MSR-Bitmap Address" and APM volume 2: 15.11 "MS
intercepts" describe MSR permission bitmaps.  Permission bitmaps are
used to control whether an execution of rdmsr or wrmsr will cause a
vm exit.  For userspace tracked MSRs it is required they cause a vm
exit, so the host is able to forward the MSR to userspace.  This change
adds vmx/svm support to ensure the permission bitmap is properly set to
cause a vm_exit to the host when rdmsr or wrmsr is used by one of the
userspace tracked MSRs.  Also, to avoid repeatedly setting them,
kvm_make_request() is used to coalesce these into a single call.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
---
 arch/x86/include/asm/kvm_host.h |  3 ++
 arch/x86/kvm/svm/svm.c          | 49 ++++++++++++++++++++++++++-------
 arch/x86/kvm/vmx/vmx.c          | 13 ++++++++-
 arch/x86/kvm/x86.c              | 16 +++++++++++
 4 files changed, 70 insertions(+), 11 deletions(-)

Comments

kernel test robot Aug. 10, 2020, 9:23 p.m. UTC | #1 
Hi Aaron,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on v5.8]
[cannot apply to kvm/linux-next next-20200810]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Aaron-Lewis/Allow-userspace-to-manage-MSRs/20200811-041443
base:    bcf876870b95592b52519ed4aafcf9d95999bc9c
config: x86_64-randconfig-a003-20200810 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 3a34228bff6fdf45b50cb57cf5fb85d659eeb672)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kvm/vmx/vmx.c:3826:6: warning: no previous prototype for function 'vmx_set_user_msr_intercept' [-Wmissing-prototypes]
   void vmx_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
        ^
   arch/x86/kvm/vmx/vmx.c:3826:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void vmx_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
   ^
   static 
   1 warning generated.
--
>> arch/x86/kvm/svm/svm.c:636:6: warning: no previous prototype for function 'svm_set_user_msr_intercept' [-Wmissing-prototypes]
   void svm_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
        ^
   arch/x86/kvm/svm/svm.c:636:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void svm_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
   ^
   static 
   1 warning generated.

vim +/vmx_set_user_msr_intercept +3826 arch/x86/kvm/vmx/vmx.c

  3825	
> 3826	void vmx_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
  3827	{
  3828		vmx_enable_intercept_for_msr(vcpu, msr, MSR_TYPE_RW);
  3829	}
  3830	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 510055471dd0..07a85f5f0b8a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -87,6 +87,7 @@ 
 #define KVM_REQ_HV_TLB_FLUSH \
 	KVM_ARCH_REQ_FLAGS(27, KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_APF_READY		KVM_ARCH_REQ(28)
+#define KVM_REQ_USER_MSR_UPDATE KVM_ARCH_REQ(29)
 
 #define CR0_RESERVED_BITS                                               \
 	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
@@ -1271,6 +1272,8 @@  struct kvm_x86_ops {
 	int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
 
 	void (*migrate_timers)(struct kvm_vcpu *vcpu);
+
+	void (*set_user_msr_intercept)(struct kvm_vcpu *vcpu, u32 msr);
 };
 
 struct kvm_x86_nested_ops {
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index eb673b59f7b7..c560d283b2af 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -583,13 +583,27 @@  static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr)
 	return !!test_bit(bit_write,  &tmp);
 }
 
+static void __set_msr_interception(u32 *msrpm, u32 msr, int read, int write,
+				   u32 offset)
+{
+	u8 bit_read, bit_write;
+	unsigned long tmp;
+
+	bit_read  = 2 * (msr & 0x0f);
+	bit_write = 2 * (msr & 0x0f) + 1;
+	tmp       = msrpm[offset];
+
+	read  ? clear_bit(bit_read,  &tmp) : set_bit(bit_read,  &tmp);
+	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
+
+	msrpm[offset] = tmp;
+}
+
 static void set_msr_interception(struct kvm_vcpu *vcpu, u32 msr, int read,
 				 int write)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	u32 *msrpm = svm->msrpm;
-	u8 bit_read, bit_write;
-	unsigned long tmp;
 	u32 offset;
 
 	/*
@@ -598,17 +612,30 @@  static void set_msr_interception(struct kvm_vcpu *vcpu, u32 msr, int read,
 	 */
 	WARN_ON(!valid_msr_intercept(msr));
 
-	offset    = svm_msrpm_offset(msr);
-	bit_read  = 2 * (msr & 0x0f);
-	bit_write = 2 * (msr & 0x0f) + 1;
-	tmp       = msrpm[offset];
-
+	offset = svm_msrpm_offset(msr);
 	BUG_ON(offset == MSR_INVALID);
 
-	read  ? clear_bit(bit_read,  &tmp) : set_bit(bit_read,  &tmp);
-	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
+	__set_msr_interception(msrpm, msr, read, write, offset);
 
-	msrpm[offset] = tmp;
+	if (read || write)
+		kvm_make_request(KVM_REQ_USER_MSR_UPDATE, vcpu);
+}
+
+static void set_user_msr_interception(struct kvm_vcpu *vcpu, u32 msr, int read,
+				      int write)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+	u32 *msrpm = svm->msrpm;
+	u32 offset;
+
+	offset = svm_msrpm_offset(msr);
+	if (offset != MSR_INVALID)
+		__set_msr_interception(msrpm, msr, read, write, offset);
+}
+
+void svm_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
+{
+	set_user_msr_interception(vcpu, msr, 0, 0);
 }
 
 static void svm_vcpu_init_msrpm(struct kvm_vcpu *vcpu, u32 *msrpm)
@@ -4088,6 +4115,8 @@  static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
 
 	.apic_init_signal_blocked = svm_apic_init_signal_blocked,
+
+	.set_user_msr_intercept = svm_set_user_msr_intercept,
 };
 
 static struct kvm_x86_init_ops svm_init_ops __initdata = {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1313e47a5a1e..3d3d9eaeca64 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3728,6 +3728,10 @@  static __always_inline void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu,
 			__clear_bit(msr, msr_bitmap + 0xc00 / f);
 
 	}
+
+	if (type & MSR_TYPE_R || type & MSR_TYPE_W) {
+		kvm_make_request(KVM_REQ_USER_MSR_UPDATE, vcpu);
+	}
 }
 
 static __always_inline void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu,
@@ -3795,7 +3799,7 @@  static u8 vmx_msr_bitmap_mode(struct kvm_vcpu *vcpu)
 }
 
 static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu,
-					 unsigned long *msr_bitmap, u8 mode)
+					unsigned long *msr_bitmap, u8 mode)
 {
 	int msr;
 
@@ -3819,6 +3823,11 @@  static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu,
 	}
 }
 
+void vmx_set_user_msr_intercept(struct kvm_vcpu *vcpu, u32 msr)
+{
+	vmx_enable_intercept_for_msr(vcpu, msr, MSR_TYPE_RW);
+}
+
 void vmx_update_msr_bitmap(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -7965,6 +7974,8 @@  static struct kvm_x86_ops vmx_x86_ops __initdata = {
 	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
 	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
 	.migrate_timers = vmx_migrate_timers,
+
+	.set_user_msr_intercept = vmx_set_user_msr_intercept,
 };
 
 static __init int hardware_setup(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4dff6147557e..b79600086bd3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3555,6 +3555,19 @@  bool kvm_msr_user_exit(struct kvm *kvm, u32 index)
 }
 EXPORT_SYMBOL_GPL(kvm_msr_user_exit);
 
+static void kvm_set_user_msr_intercepts(struct kvm_vcpu *vcpu)
+{
+	struct kvm_msr_list *msr_list = vcpu->kvm->arch.user_exit_msrs;
+	u32 i, msr;
+
+	if (msr_list) {
+		for (i = 0; i < msr_list->nmsrs; i++) {
+			msr = msr_list->indices[i];
+			kvm_x86_ops.set_user_msr_intercept(vcpu, msr);
+		}
+	}
+}
+
 int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 {
 	int r = 0;
@@ -8583,6 +8596,9 @@  static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			kvm_vcpu_update_apicv(vcpu);
 		if (kvm_check_request(KVM_REQ_APF_READY, vcpu))
 			kvm_check_async_pf_completion(vcpu);
+
+		if (kvm_check_request(KVM_REQ_USER_MSR_UPDATE, vcpu))
+			kvm_set_user_msr_intercepts(vcpu);
 	}
 
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {