[PATCH v1] x86/hvm: Add MSR old value

[PATCH v1] x86/hvm: Add MSR old value

[Alexandru Isaila]

This patch adds the old value param and the onchangeonly option
to the VM_EVENT_REASON_MOV_TO_MSR event.

The param was added to the vm_event_mov_to_msr struct and to the
hvm_monitor_msr function. Finally I've changed the bool_t param
to a bool for the hvm_msr_write_intercept function.

Signed-off-by: Alexandru Isaila <aisaila@bitdefender.com>
---
 tools/libxc/include/xenctrl.h     |  2 +-
 tools/libxc/xc_monitor.c          |  3 ++-
 xen/arch/x86/hvm/hvm.c            | 10 ++++++++--
 xen/arch/x86/hvm/monitor.c        |  9 ++++++---
 xen/arch/x86/monitor.c            | 26 +++++++++++++++++++++++---
 xen/include/asm-x86/hvm/monitor.h |  2 +-
 xen/include/asm-x86/hvm/support.h |  2 +-
 xen/include/asm-x86/monitor.h     |  2 ++
 xen/include/public/domctl.h       |  2 ++
 xen/include/public/vm_event.h     |  5 +++--
 10 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 3bcab3c..b99d6eb 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2048,7 +2048,7 @@ int xc_monitor_write_ctrlreg(xc_interface *xch, domid_t domain_id,
  * non-architectural indices.
  */
 int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, uint32_t msr,
-                          bool enable);
+                          bool enable, bool onchangeonly);
 int xc_monitor_singlestep(xc_interface *xch, domid_t domain_id, bool enable);
 int xc_monitor_software_breakpoint(xc_interface *xch, domid_t domain_id,
                                    bool enable);
diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
index 6046680..09d04be 100644
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -90,7 +90,7 @@ int xc_monitor_write_ctrlreg(xc_interface *xch, domid_t domain_id,
 }
 
 int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, uint32_t msr,
-                          bool enable)
+                          bool enable, bool onchangeonly)
 {
     DECLARE_DOMCTL;
 
@@ -100,6 +100,7 @@ int xc_monitor_mov_to_msr(xc_interface *xch, domid_t domain_id, uint32_t msr,
                                     : XEN_DOMCTL_MONITOR_OP_DISABLE;
     domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR;
     domctl.u.monitor_op.u.mov_to_msr.msr = msr;
+    domctl.u.monitor_op.u.mov_to_msr.onchangeonly = onchangeonly;
 
     return do_domctl(xch, &domctl);
 }
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 205b4cb..0238787 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3489,7 +3489,7 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t *msr_content)
 }
 
 int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
-                            bool_t may_defer)
+                            bool may_defer)
 {
     struct vcpu *v = current;
     struct domain *d = v->domain;
@@ -3500,6 +3500,12 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
 
     if ( may_defer && unlikely(monitored_msr(v->domain, msr)) )
     {
+        uint64_t msr_old_content;
+
+        ret = hvm_msr_read_intercept(msr, &msr_old_content);
+        if ( ret != X86EMUL_OKAY )
+            return ret;
+
         ASSERT(v->arch.vm_event);
 
         /* The actual write will occur in hvm_do_resume() (if permitted). */
@@ -3507,7 +3513,7 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
         v->arch.vm_event->write_data.msr = msr;
         v->arch.vm_event->write_data.value = msr_content;
 
-        hvm_monitor_msr(msr, msr_content);
+        hvm_monitor_msr(msr, msr_content, msr_old_content);
         return X86EMUL_OKAY;
     }
 
diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
index 4ce778c..74f83b4 100644
--- a/xen/arch/x86/hvm/monitor.c
+++ b/xen/arch/x86/hvm/monitor.c
@@ -74,16 +74,19 @@ bool hvm_monitor_emul_unimplemented(void)
         monitor_traps(curr, true, &req) == 1;
 }
 
-void hvm_monitor_msr(unsigned int msr, uint64_t value)
+void hvm_monitor_msr(unsigned int msr, uint64_t new_value, uint64_t old_value)
 {
     struct vcpu *curr = current;
 
-    if ( monitored_msr(curr->domain, msr) )
+    if ( monitored_msr(curr->domain, msr) &&
+         ( !monitored_msr_onchangeonly(curr->domain, msr) ||
+           new_value != old_value ) )
     {
         vm_event_request_t req = {
             .reason = VM_EVENT_REASON_MOV_TO_MSR,
             .u.mov_to_msr.msr = msr,
-            .u.mov_to_msr.value = value,
+            .u.mov_to_msr.new_value = new_value,
+            .u.mov_to_msr.old_value = old_value
         };
 
         monitor_traps(curr, 1, &req);
diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index e59f1f5..a3046c6 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -25,7 +25,7 @@
 int arch_monitor_init_domain(struct domain *d)
 {
     if ( !d->arch.monitor.msr_bitmap )
-        d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
+        d->arch.monitor.msr_bitmap = xzalloc_array(struct monitor_msr_bitmap, 2);
 
     if ( !d->arch.monitor.msr_bitmap )
         return -ENOMEM;
@@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const struct domain *d, u32 *msr)
     }
 }
 
-static int monitor_enable_msr(struct domain *d, u32 msr)
+static int monitor_enable_msr(struct domain *d, u32 msr, bool onchangeonly)
 {
     unsigned long *bitmap;
     u32 index = msr;
@@ -84,6 +84,11 @@ static int monitor_enable_msr(struct domain *d, u32 msr)
 
     hvm_enable_msr_interception(d, msr);
 
+    if( onchangeonly )
+        __set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
+    else
+        __clear_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
+
     return 0;
 }
 
@@ -119,6 +124,21 @@ bool monitored_msr(const struct domain *d, u32 msr)
     return test_bit(msr, bitmap);
 }
 
+bool monitored_msr_onchangeonly(const struct domain *d, u32 msr)
+{
+    const unsigned long *bitmap;
+
+    if ( !d->arch.monitor.msr_bitmap )
+        return false;
+
+    bitmap = monitor_bitmap_for_msr(d, &msr);
+
+    if ( !bitmap )
+        return false;
+
+    return test_bit(msr + sizeof(struct monitor_msr_bitmap), bitmap);
+}
+
 int arch_monitor_domctl_event(struct domain *d,
                               struct xen_domctl_monitor_op *mop)
 {
@@ -198,7 +218,7 @@ int arch_monitor_domctl_event(struct domain *d,
         }
 
         if ( requested_status )
-            rc = monitor_enable_msr(d, msr);
+            rc = monitor_enable_msr(d, msr, mop->u.mov_to_msr.onchangeonly);
         else
             rc = monitor_disable_msr(d, msr);
 
diff --git a/xen/include/asm-x86/hvm/monitor.h b/xen/include/asm-x86/hvm/monitor.h
index 6e22091..260d7b0 100644
--- a/xen/include/asm-x86/hvm/monitor.h
+++ b/xen/include/asm-x86/hvm/monitor.h
@@ -37,7 +37,7 @@ bool hvm_monitor_cr(unsigned int index, unsigned long value,
                     unsigned long old);
 #define hvm_monitor_crX(cr, new, old) \
                         hvm_monitor_cr(VM_EVENT_X86_##cr, new, old)
-void hvm_monitor_msr(unsigned int msr, uint64_t value);
+void hvm_monitor_msr(unsigned int msr, uint64_t new_value, uint64_t old_value);
 void hvm_monitor_descriptor_access(uint64_t exit_info,
                                    uint64_t vmx_exit_qualification,
                                    uint8_t descriptor, bool is_write);
diff --git a/xen/include/asm-x86/hvm/support.h b/xen/include/asm-x86/hvm/support.h
index d784fc1..ac33eea 100644
--- a/xen/include/asm-x86/hvm/support.h
+++ b/xen/include/asm-x86/hvm/support.h
@@ -154,7 +154,7 @@ void hvm_ud_intercept(struct cpu_user_regs *);
 int __must_check hvm_msr_read_intercept(
     unsigned int msr, uint64_t *msr_content);
 int __must_check hvm_msr_write_intercept(
-    unsigned int msr, uint64_t msr_content, bool_t may_defer);
+    unsigned int msr, uint64_t msr_content, bool may_defer);
 
 #endif /* __ASM_X86_HVM_SUPPORT_H__ */
 
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 0ada970..575b3c6 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -105,4 +105,6 @@ void arch_monitor_cleanup_domain(struct domain *d);
 
 bool monitored_msr(const struct domain *d, u32 msr);
 
+bool monitored_msr_onchangeonly(const struct domain *d, u32 msr);
+
 #endif /* __ASM_X86_MONITOR_H__ */
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 8853445..3dfadae 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1046,6 +1046,8 @@ struct xen_domctl_monitor_op {
 
         struct {
             uint32_t msr;
+            /* Send event only on a change of value */
+            uint8_t onchangeonly;
         } mov_to_msr;
 
         struct {
diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index b531f71..36e3f46 100644
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -29,7 +29,7 @@
 
 #include "xen.h"
 
-#define VM_EVENT_INTERFACE_VERSION 0x00000002
+#define VM_EVENT_INTERFACE_VERSION 0x00000003
 
 #if defined(__XEN__) || defined(__XEN_TOOLS__)
 
@@ -260,7 +260,8 @@ struct vm_event_debug {
 
 struct vm_event_mov_to_msr {
     uint64_t msr;
-    uint64_t value;
+    uint64_t new_value;
+    uint64_t old_value;
 };
 
 #define VM_EVENT_DESC_IDTR           1
-- 
2.7.4


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Re: [PATCH v1] x86/hvm: Add MSR old value

[Tamas K Lengyel]

On Thu, Oct 12, 2017 at 3:10 AM, Alexandru Isaila
<aisaila@bitdefender.com> wrote:
> This patch adds the old value param and the onchangeonly option
> to the VM_EVENT_REASON_MOV_TO_MSR event.
>
> The param was added to the vm_event_mov_to_msr struct and to the
> hvm_monitor_msr function. Finally I've changed the bool_t param
> to a bool for the hvm_msr_write_intercept function.
>
> Signed-off-by: Alexandru Isaila <aisaila@bitdefender.com>

Acked-by: Tamas K Lengyel <tamas@tklengyel.com>

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Re: [PATCH v1] x86/hvm: Add MSR old value

[Jan Beulich]

>>> On 12.10.17 at 11:10, <aisaila@bitdefender.com> wrote:
> --- a/xen/arch/x86/hvm/monitor.c
> +++ b/xen/arch/x86/hvm/monitor.c
> @@ -74,16 +74,19 @@ bool hvm_monitor_emul_unimplemented(void)
>          monitor_traps(curr, true, &req) == 1;
>  }
>  
> -void hvm_monitor_msr(unsigned int msr, uint64_t value)
> +void hvm_monitor_msr(unsigned int msr, uint64_t new_value, uint64_t old_value)
>  {
>      struct vcpu *curr = current;
>  
> -    if ( monitored_msr(curr->domain, msr) )
> +    if ( monitored_msr(curr->domain, msr) &&
> +         ( !monitored_msr_onchangeonly(curr->domain, msr) ||
> +           new_value != old_value ) )

Stray blanks inside the inner parentheses.

> @@ -84,6 +84,11 @@ static int monitor_enable_msr(struct domain *d, u32 msr)
>  
>      hvm_enable_msr_interception(d, msr);
>  
> +    if( onchangeonly )

Style.

> +        __set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);

I think you miss "* 8" here - a bit position plus sizeof() doesn't
produce any useful value.

But what's worse - having read till the end of the patch I don't
see you change any allocation, yet you clearly need to double
the space now that you need two bits per MSR.

> --- a/xen/include/asm-x86/monitor.h
> +++ b/xen/include/asm-x86/monitor.h
> @@ -105,4 +105,6 @@ void arch_monitor_cleanup_domain(struct domain *d);
>  
>  bool monitored_msr(const struct domain *d, u32 msr);
>  
> +bool monitored_msr_onchangeonly(const struct domain *d, u32 msr);
> +

Them belonging together, please have them together (without an
intervening blank line).

Jan


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Re: [PATCH v1] x86/hvm: Add MSR old value

[Razvan Cojocaru]

On 13.10.2017 13:29, Jan Beulich wrote:
>> +        __set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
> 
> I think you miss "* 8" here - a bit position plus sizeof() doesn't
> produce any useful value.
> 
> But what's worse - having read till the end of the patch I don't
> see you change any allocation, yet you clearly need to double
> the space now that you need two bits per MSR.

We did this:

diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index e59f1f5..a3046c6 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -25,7 +25,7 @@
  int arch_monitor_init_domain(struct domain *d)
  {
      if ( !d->arch.monitor.msr_bitmap )
-        d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
+        d->arch.monitor.msr_bitmap = xzalloc_array(struct 
monitor_msr_bitmap, 2);

      if ( !d->arch.monitor.msr_bitmap )
          return -ENOMEM;
@@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const 
struct domain *d, u32 *msr)
      }
  }

I.e., we are now allocating an array of size 2 of struct 
monitor_msr_bitmaps with xzalloc_array().


Thanks,
Razvan

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Re: [PATCH v1] x86/hvm: Add MSR old value

[Jan Beulich]

>>> On 13.10.17 at 12:36, <rcojocaru@bitdefender.com> wrote:
> On 13.10.2017 13:29, Jan Beulich wrote:
>>> +        __set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
>> 
>> I think you miss "* 8" here - a bit position plus sizeof() doesn't
>> produce any useful value.
>> 
>> But what's worse - having read till the end of the patch I don't
>> see you change any allocation, yet you clearly need to double
>> the space now that you need two bits per MSR.
> 
> We did this:
> 
> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
> index e59f1f5..a3046c6 100644
> --- a/xen/arch/x86/monitor.c
> +++ b/xen/arch/x86/monitor.c
> @@ -25,7 +25,7 @@
>   int arch_monitor_init_domain(struct domain *d)
>   {
>       if ( !d->arch.monitor.msr_bitmap )
> -        d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
> +        d->arch.monitor.msr_bitmap = xzalloc_array(struct monitor_msr_bitmap, 2);
> 
>       if ( !d->arch.monitor.msr_bitmap )
>           return -ENOMEM;
> @@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const struct domain *d, u32 *msr)
>       }
>   }
> 
> I.e., we are now allocating an array of size 2 of struct 
> monitor_msr_bitmaps with xzalloc_array().

Oh, I'm not sure how I could overlook this considering that I
specifically looked up the allocation point and searched through
the patch for a respective change. I'm sorry for the noise in
this regard. I do think though that the chosen model is a little
odd and fragile, but that's something you and Tamas as the
maintainers of the code have to judge about.

Jan


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Re: [PATCH v1] x86/hvm: Add MSR old value

[Tamas K Lengyel]

On Fri, Oct 13, 2017 at 6:17 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 13.10.17 at 12:36, <rcojocaru@bitdefender.com> wrote:
>> On 13.10.2017 13:29, Jan Beulich wrote:
>>>> +        __set_bit(index + sizeof(struct monitor_msr_bitmap), bitmap);
>>>
>>> I think you miss "* 8" here - a bit position plus sizeof() doesn't
>>> produce any useful value.
>>>
>>> But what's worse - having read till the end of the patch I don't
>>> see you change any allocation, yet you clearly need to double
>>> the space now that you need two bits per MSR.
>>
>> We did this:
>>
>> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
>> index e59f1f5..a3046c6 100644
>> --- a/xen/arch/x86/monitor.c
>> +++ b/xen/arch/x86/monitor.c
>> @@ -25,7 +25,7 @@
>>   int arch_monitor_init_domain(struct domain *d)
>>   {
>>       if ( !d->arch.monitor.msr_bitmap )
>> -        d->arch.monitor.msr_bitmap = xzalloc(struct monitor_msr_bitmap);
>> +        d->arch.monitor.msr_bitmap = xzalloc_array(struct monitor_msr_bitmap, 2);
>>
>>       if ( !d->arch.monitor.msr_bitmap )
>>           return -ENOMEM;
>> @@ -67,7 +67,7 @@ static unsigned long *monitor_bitmap_for_msr(const struct domain *d, u32 *msr)
>>       }
>>   }
>>
>> I.e., we are now allocating an array of size 2 of struct
>> monitor_msr_bitmaps with xzalloc_array().
>
> Oh, I'm not sure how I could overlook this considering that I
> specifically looked up the allocation point and searched through
> the patch for a respective change. I'm sorry for the noise in
> this regard. I do think though that the chosen model is a little
> odd and fragile, but that's something you and Tamas as the
> maintainers of the code have to judge about.
>

It looks fine to me.

Thanks,
Tamas

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Re: [PATCH v1] x86/hvm: Add MSR old value

[Wei Liu]

On Thu, Oct 12, 2017 at 12:10:25PM +0300, Alexandru Isaila wrote:
> This patch adds the old value param and the onchangeonly option
> to the VM_EVENT_REASON_MOV_TO_MSR event.
> 
> The param was added to the vm_event_mov_to_msr struct and to the
> hvm_monitor_msr function. Finally I've changed the bool_t param
> to a bool for the hvm_msr_write_intercept function.
> 
> Signed-off-by: Alexandru Isaila <aisaila@bitdefender.com>
> ---
>  tools/libxc/include/xenctrl.h     |  2 +-
>  tools/libxc/xc_monitor.c          |  3 ++-

Acked-by: Wei Liu <wei.liu2@citrix.com>

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