[Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Jingqi Liu]

Add the option split-lock-ac to control whether the #AC
exception is generated for split locked accesses, which
is introduced for the machine, there is an example to enable it:
-machine split-lock-ac=on
It is disabled on default.

When bit 29 of the MSR (33H) is set, the processor
causes an #AC exception to be issued instead of suppressing LOCK on
bus(during split lock access).

Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
---
 accel/kvm/kvm-all.c       | 10 ++++++++++
 hw/core/machine.c         | 19 +++++++++++++++++++
 include/hw/boards.h       |  1 +
 linux-headers/linux/kvm.h |  1 +
 qemu-options.hx           |  3 +++
 5 files changed, 34 insertions(+)

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index eb7db92..e960a4d 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -1699,6 +1699,16 @@ static int kvm_init(MachineState *ms)
 
     s->sync_mmu = !!kvm_vm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);
 
+    if (ms->split_lock_ac &&
+        kvm_check_extension(s, KVM_CAP_X86_SPLIT_LOCK_AC)) {
+        ret = kvm_vm_enable_cap(s, KVM_CAP_X86_SPLIT_LOCK_AC, 0);
+        if (ret) {
+            fprintf(stderr, "Could not enable the feature that #AC exception"
+                    "will be generated for split lock accesses!\n");
+            goto err;
+        }
+    }
+
     return 0;
 
 err:
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 617e5f8..e054119 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -350,6 +350,22 @@ static void machine_set_memory_encryption(Object *obj, const char *value,
     ms->memory_encryption = g_strdup(value);
 }
 
+static void machine_set_split_lock_ac(Object *obj, bool value,
+                                      Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    ms->split_lock_ac = value;
+}
+
+static bool machine_get_split_lock_ac(Object *obj, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    return ms->split_lock_ac;
+}
+
+
 void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const char *type)
 {
     strList *item = g_new0(strList, 1);
@@ -634,6 +650,9 @@ static void machine_class_init(ObjectClass *oc, void *data)
         &error_abort);
     object_class_property_set_description(oc, "memory-encryption",
         "Set memory encyption object to use", &error_abort);
+    object_class_property_add_bool(oc, "split-lock-ac",
+        machine_get_split_lock_ac, machine_set_split_lock_ac,
+        &error_abort);
 }
 
 static void machine_class_base_init(ObjectClass *oc, void *data)
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 79069dd..9c1e2c0 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -256,6 +256,7 @@ struct MachineState {
     bool suppress_vmdesc;
     bool enforce_config_section;
     bool enable_graphics;
+    bool split_lock_ac;
     char *memory_encryption;
     DeviceMemoryState *device_memory;
 
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index 98f389a..4bfa879 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_GET_MSR_FEATURES 153
 #define KVM_CAP_HYPERV_EVENTFD 154
 #define KVM_CAP_HYPERV_TLBFLUSH 155
+#define KVM_CAP_X86_SPLIT_LOCK_AC 156
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/qemu-options.hx b/qemu-options.hx
index 81b1e99..935cefe 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -44,6 +44,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "                nvdimm=on|off controls NVDIMM support (default=off)\n"
     "                enforce-config-section=on|off enforce configuration section migration (default=off)\n"
     "                s390-squash-mcss=on|off (deprecated) controls support for squashing into default css (default=off)\n"
+    "                split-lock-ac=on|off controls support #AC exception for split locked accesses (default=off)\n"
     "                memory-encryption=@var{} memory encryption object to use (default=none)\n",
     QEMU_ARCH_ALL)
 STEXI
@@ -113,6 +114,8 @@ NOTE: this parameter is deprecated. Please use @option{-global}
 @option{migration.send-configuration}=@var{on|off} instead.
 @item memory-encryption=@var{}
 Memory encryption object to use. The default is none.
+@item split-lock-ac=on|off
+Enables or disables #AC exception for split locked accesses.
 @end table
 ETEXI
 
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Paolo Bonzini]

On 04/07/2018 15:12, Jingqi Liu wrote:
> Add the option split-lock-ac to control whether the #AC
> exception is generated for split locked accesses, which
> is introduced for the machine, there is an example to enable it:
> -machine split-lock-ac=on
> It is disabled on default.
> 
> When bit 29 of the MSR (33H) is set, the processor
> causes an #AC exception to be issued instead of suppressing LOCK on
> bus(during split lock access).

This should be a CPU feature, not a machine feature.  As mentioned in
the review of the kernel patch, please work with Robert to use the same
infrastructure for both MSR_TEST_CTL and MSR_IA32_ARCH_CAPABILITIES.

(Robert, does IceLake have this feature?  If so, we cannot create the
CPU model until everything is in place).

BTW, why is the availability of the feature not exposed with a CPUID
bit?  It doesn't make much sense.

Paolo

> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
> ---
>  accel/kvm/kvm-all.c       | 10 ++++++++++
>  hw/core/machine.c         | 19 +++++++++++++++++++
>  include/hw/boards.h       |  1 +
>  linux-headers/linux/kvm.h |  1 +
>  qemu-options.hx           |  3 +++
>  5 files changed, 34 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index eb7db92..e960a4d 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -1699,6 +1699,16 @@ static int kvm_init(MachineState *ms)
>  
>      s->sync_mmu = !!kvm_vm_check_extension(kvm_state, KVM_CAP_SYNC_MMU);
>  
> +    if (ms->split_lock_ac &&
> +        kvm_check_extension(s, KVM_CAP_X86_SPLIT_LOCK_AC)) {
> +        ret = kvm_vm_enable_cap(s, KVM_CAP_X86_SPLIT_LOCK_AC, 0);
> +        if (ret) {
> +            fprintf(stderr, "Could not enable the feature that #AC exception"
> +                    "will be generated for split lock accesses!\n");
> +            goto err;
> +        }
> +    }
> +
>      return 0;
>  
>  err:
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 617e5f8..e054119 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -350,6 +350,22 @@ static void machine_set_memory_encryption(Object *obj, const char *value,
>      ms->memory_encryption = g_strdup(value);
>  }
>  
> +static void machine_set_split_lock_ac(Object *obj, bool value,
> +                                      Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    ms->split_lock_ac = value;
> +}
> +
> +static bool machine_get_split_lock_ac(Object *obj, Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    return ms->split_lock_ac;
> +}
> +
> +
>  void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const char *type)
>  {
>      strList *item = g_new0(strList, 1);
> @@ -634,6 +650,9 @@ static void machine_class_init(ObjectClass *oc, void *data)
>          &error_abort);
>      object_class_property_set_description(oc, "memory-encryption",
>          "Set memory encyption object to use", &error_abort);
> +    object_class_property_add_bool(oc, "split-lock-ac",
> +        machine_get_split_lock_ac, machine_set_split_lock_ac,
> +        &error_abort);
>  }
>  
>  static void machine_class_base_init(ObjectClass *oc, void *data)
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 79069dd..9c1e2c0 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -256,6 +256,7 @@ struct MachineState {
>      bool suppress_vmdesc;
>      bool enforce_config_section;
>      bool enable_graphics;
> +    bool split_lock_ac;
>      char *memory_encryption;
>      DeviceMemoryState *device_memory;
>  
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index 98f389a..4bfa879 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_GET_MSR_FEATURES 153
>  #define KVM_CAP_HYPERV_EVENTFD 154
>  #define KVM_CAP_HYPERV_TLBFLUSH 155
> +#define KVM_CAP_X86_SPLIT_LOCK_AC 156
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 81b1e99..935cefe 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -44,6 +44,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>      "                nvdimm=on|off controls NVDIMM support (default=off)\n"
>      "                enforce-config-section=on|off enforce configuration section migration (default=off)\n"
>      "                s390-squash-mcss=on|off (deprecated) controls support for squashing into default css (default=off)\n"
> +    "                split-lock-ac=on|off controls support #AC exception for split locked accesses (default=off)\n"
>      "                memory-encryption=@var{} memory encryption object to use (default=none)\n",
>      QEMU_ARCH_ALL)
>  STEXI
> @@ -113,6 +114,8 @@ NOTE: this parameter is deprecated. Please use @option{-global}
>  @option{migration.send-configuration}=@var{on|off} instead.
>  @item memory-encryption=@var{}
>  Memory encryption object to use. The default is none.
> +@item split-lock-ac=on|off
> +Enables or disables #AC exception for split locked accesses.
>  @end table
>  ETEXI
>  
> 

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[no-reply]

Hi,

This series failed build test on s390x host. Please find the details below.

N/A. Internal error while reading log file



---
Email generated automatically by Patchew [http://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Eduardo Habkost]

On Wed, Jul 04, 2018 at 03:38:32PM +0200, Paolo Bonzini wrote:
> On 04/07/2018 15:12, Jingqi Liu wrote:
> > Add the option split-lock-ac to control whether the #AC
> > exception is generated for split locked accesses, which
> > is introduced for the machine, there is an example to enable it:
> > -machine split-lock-ac=on
> > It is disabled on default.
> > 
> > When bit 29 of the MSR (33H) is set, the processor
> > causes an #AC exception to be issued instead of suppressing LOCK on
> > bus(during split lock access).
> 
> This should be a CPU feature, not a machine feature.  As mentioned in
> the review of the kernel patch, please work with Robert to use the same
> infrastructure for both MSR_TEST_CTL and MSR_IA32_ARCH_CAPABILITIES.
> 
> (Robert, does IceLake have this feature?  If so, we cannot create the
> CPU model until everything is in place).

I don't think we need to block the CPU model because QEMU+KVM
doesn't support some features yet, as long as kernel versions
capable of running the 3.0 version of IceLake-Server will be also
capable of running the 3.1 version of IceLake-Server.

Now, if that condition won't be true and we have some IceLake
features that will added only to more recent kernels, it might be
a good idea to hold the inclusion of the CPU model until
everything is in place.


> 
> BTW, why is the availability of the feature not exposed with a CPUID
> bit?  It doesn't make much sense.

I have the same question.  Without a CPUID bit, guests may block
the VM from being migrated to older hosts because the additional
section for the MSR will appear.

-- 
Eduardo

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Hu, Robert]

Best Regards,
Robert Hoo

> -----Original Message-----
> From: Paolo Bonzini <pbonzini@redhat.com>
> Sent: Wednesday, July 4, 2018 21:39
> To: Liu, Jingqi <jingqi.liu@intel.com>
> Cc: rth@twiddle.net; ehabkost@redhat.com; mtosatti@redhat.com; qemu-
> devel@nongnu.org; Wang, Wei W <wei.w.wang@intel.com>; Hu, Robert
> <robert.hu@intel.com>
> Subject: Re: [PATCH] kvm: x86: Add support for -machine split-lock-ac
> 
> On 04/07/2018 15:12, Jingqi Liu wrote:
> > Add the option split-lock-ac to control whether the #AC exception is
> > generated for split locked accesses, which is introduced for the
> > machine, there is an example to enable it:
> > -machine split-lock-ac=on
> > It is disabled on default.
> >
> > When bit 29 of the MSR (33H) is set, the processor causes an #AC
> > exception to be issued instead of suppressing LOCK on bus(during split
> > lock access).
> 
> This should be a CPU feature, not a machine feature.  As mentioned in the
> review of the kernel patch, please work with Robert to use the same
> infrastructure for both MSR_TEST_CTL and MSR_IA32_ARCH_CAPABILITIES.
> 
> (Robert, does IceLake have this feature?  If so, we cannot create the CPU model
> until everything is in place).

[Robert Hoo] 
Hi Paolo,
This is not an Icelake  feature.
> 
> BTW, why is the availability of the feature not exposed with a CPUID bit?  It
> doesn't make much sense.
> 
> Paolo
> 
> > Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
> > ---
> >  accel/kvm/kvm-all.c       | 10 ++++++++++
> >  hw/core/machine.c         | 19 +++++++++++++++++++
> >  include/hw/boards.h       |  1 +
> >  linux-headers/linux/kvm.h |  1 +
> >  qemu-options.hx           |  3 +++
> >  5 files changed, 34 insertions(+)
> >
> > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index
> > eb7db92..e960a4d 100644
> > --- a/accel/kvm/kvm-all.c
> > +++ b/accel/kvm/kvm-all.c
> > @@ -1699,6 +1699,16 @@ static int kvm_init(MachineState *ms)
> >
> >      s->sync_mmu = !!kvm_vm_check_extension(kvm_state,
> > KVM_CAP_SYNC_MMU);
> >
> > +    if (ms->split_lock_ac &&
> > +        kvm_check_extension(s, KVM_CAP_X86_SPLIT_LOCK_AC)) {
> > +        ret = kvm_vm_enable_cap(s, KVM_CAP_X86_SPLIT_LOCK_AC, 0);
> > +        if (ret) {
> > +            fprintf(stderr, "Could not enable the feature that #AC exception"
> > +                    "will be generated for split lock accesses!\n");
> > +            goto err;
> > +        }
> > +    }
> > +
> >      return 0;
> >
> >  err:
> > diff --git a/hw/core/machine.c b/hw/core/machine.c index
> > 617e5f8..e054119 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -350,6 +350,22 @@ static void machine_set_memory_encryption(Object
> *obj, const char *value,
> >      ms->memory_encryption = g_strdup(value);  }
> >
> > +static void machine_set_split_lock_ac(Object *obj, bool value,
> > +                                      Error **errp) {
> > +    MachineState *ms = MACHINE(obj);
> > +
> > +    ms->split_lock_ac = value;
> > +}
> > +
> > +static bool machine_get_split_lock_ac(Object *obj, Error **errp) {
> > +    MachineState *ms = MACHINE(obj);
> > +
> > +    return ms->split_lock_ac;
> > +}
> > +
> > +
> >  void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const
> > char *type)  {
> >      strList *item = g_new0(strList, 1); @@ -634,6 +650,9 @@ static
> > void machine_class_init(ObjectClass *oc, void *data)
> >          &error_abort);
> >      object_class_property_set_description(oc, "memory-encryption",
> >          "Set memory encyption object to use", &error_abort);
> > +    object_class_property_add_bool(oc, "split-lock-ac",
> > +        machine_get_split_lock_ac, machine_set_split_lock_ac,
> > +        &error_abort);
> >  }
> >
> >  static void machine_class_base_init(ObjectClass *oc, void *data) diff
> > --git a/include/hw/boards.h b/include/hw/boards.h index
> > 79069dd..9c1e2c0 100644
> > --- a/include/hw/boards.h
> > +++ b/include/hw/boards.h
> > @@ -256,6 +256,7 @@ struct MachineState {
> >      bool suppress_vmdesc;
> >      bool enforce_config_section;
> >      bool enable_graphics;
> > +    bool split_lock_ac;
> >      char *memory_encryption;
> >      DeviceMemoryState *device_memory;
> >
> > diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> > index 98f389a..4bfa879 100644
> > --- a/linux-headers/linux/kvm.h
> > +++ b/linux-headers/linux/kvm.h
> > @@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {  #define
> > KVM_CAP_GET_MSR_FEATURES 153  #define KVM_CAP_HYPERV_EVENTFD
> 154
> > #define KVM_CAP_HYPERV_TLBFLUSH 155
> > +#define KVM_CAP_X86_SPLIT_LOCK_AC 156
> >
> >  #ifdef KVM_CAP_IRQ_ROUTING
> >
> > diff --git a/qemu-options.hx b/qemu-options.hx index 81b1e99..935cefe
> > 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -44,6 +44,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
> >      "                nvdimm=on|off controls NVDIMM support (default=off)\n"
> >      "                enforce-config-section=on|off enforce configuration section
> migration (default=off)\n"
> >      "                s390-squash-mcss=on|off (deprecated) controls support for
> squashing into default css (default=off)\n"
> > +    "                split-lock-ac=on|off controls support #AC exception for split
> locked accesses (default=off)\n"
> >      "                memory-encryption=@var{} memory encryption object to use
> (default=none)\n",
> >      QEMU_ARCH_ALL)
> >  STEXI
> > @@ -113,6 +114,8 @@ NOTE: this parameter is deprecated. Please use
> > @option{-global}  @option{migration.send-configuration}=@var{on|off}
> instead.
> >  @item memory-encryption=@var{}
> >  Memory encryption object to use. The default is none.
> > +@item split-lock-ac=on|off
> > +Enables or disables #AC exception for split locked accesses.
> >  @end table
> >  ETEXI
> >
> >

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Paolo Bonzini]

On 04/07/2018 19:52, Eduardo Habkost wrote:
>> (Robert, does IceLake have this feature?  If so, we cannot create the
>> CPU model until everything is in place).
> I don't think we need to block the CPU model because QEMU+KVM
> doesn't support some features yet, as long as kernel versions
> capable of running the 3.0 version of IceLake-Server will be also
> capable of running the 3.1 version of IceLake-Server.
> 
> Now, if that condition won't be true and we have some IceLake
> features that will added only to more recent kernels, it might be
> a good idea to hold the inclusion of the CPU model until
> everything is in place.
> 
> 

Yeah, the reason for that is to wait for the kernel side of the
implementation.

Paolo

Re: [Qemu-devel] [PATCH] kvm: x86: Add support for -machine split-lock-ac

[Paolo Bonzini]

On 05/07/2018 10:45, Hu, Robert wrote:
>> This should be a CPU feature, not a machine feature.  As mentioned in the
>> review of the kernel patch, please work with Robert to use the same
>> infrastructure for both MSR_TEST_CTL and MSR_IA32_ARCH_CAPABILITIES.
>>
>> (Robert, does IceLake have this feature?  If so, we cannot create the CPU model
>> until everything is in place).
> 
> [Robert Hoo] 
> Hi Paolo,
> This is not an Icelake  feature.

So why is Intel pushing operating system code for half-baked features?
This "MSRs are the new CPUID" attitude must stop.

Paolo

>> BTW, why is the availability of the feature not exposed with a CPUID bit?  It
>> doesn't make much sense.
>>
>> Paolo
>>
>>> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
>>> ---
>>>  accel/kvm/kvm-all.c       | 10 ++++++++++
>>>  hw/core/machine.c         | 19 +++++++++++++++++++
>>>  include/hw/boards.h       |  1 +
>>>  linux-headers/linux/kvm.h |  1 +
>>>  qemu-options.hx           |  3 +++
>>>  5 files changed, 34 insertions(+)
>>>
>>> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index
>>> eb7db92..e960a4d 100644
>>> --- a/accel/kvm/kvm-all.c
>>> +++ b/accel/kvm/kvm-all.c
>>> @@ -1699,6 +1699,16 @@ static int kvm_init(MachineState *ms)
>>>
>>>      s->sync_mmu = !!kvm_vm_check_extension(kvm_state,
>>> KVM_CAP_SYNC_MMU);
>>>
>>> +    if (ms->split_lock_ac &&
>>> +        kvm_check_extension(s, KVM_CAP_X86_SPLIT_LOCK_AC)) {
>>> +        ret = kvm_vm_enable_cap(s, KVM_CAP_X86_SPLIT_LOCK_AC, 0);
>>> +        if (ret) {
>>> +            fprintf(stderr, "Could not enable the feature that #AC exception"
>>> +                    "will be generated for split lock accesses!\n");
>>> +            goto err;
>>> +        }
>>> +    }
>>> +
>>>      return 0;
>>>
>>>  err:
>>> diff --git a/hw/core/machine.c b/hw/core/machine.c index
>>> 617e5f8..e054119 100644
>>> --- a/hw/core/machine.c
>>> +++ b/hw/core/machine.c
>>> @@ -350,6 +350,22 @@ static void machine_set_memory_encryption(Object
>> *obj, const char *value,
>>>      ms->memory_encryption = g_strdup(value);  }
>>>
>>> +static void machine_set_split_lock_ac(Object *obj, bool value,
>>> +                                      Error **errp) {
>>> +    MachineState *ms = MACHINE(obj);
>>> +
>>> +    ms->split_lock_ac = value;
>>> +}
>>> +
>>> +static bool machine_get_split_lock_ac(Object *obj, Error **errp) {
>>> +    MachineState *ms = MACHINE(obj);
>>> +
>>> +    return ms->split_lock_ac;
>>> +}
>>> +
>>> +
>>>  void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const
>>> char *type)  {
>>>      strList *item = g_new0(strList, 1); @@ -634,6 +650,9 @@ static
>>> void machine_class_init(ObjectClass *oc, void *data)
>>>          &error_abort);
>>>      object_class_property_set_description(oc, "memory-encryption",
>>>          "Set memory encyption object to use", &error_abort);
>>> +    object_class_property_add_bool(oc, "split-lock-ac",
>>> +        machine_get_split_lock_ac, machine_set_split_lock_ac,
>>> +        &error_abort);
>>>  }
>>>
>>>  static void machine_class_base_init(ObjectClass *oc, void *data) diff
>>> --git a/include/hw/boards.h b/include/hw/boards.h index
>>> 79069dd..9c1e2c0 100644
>>> --- a/include/hw/boards.h
>>> +++ b/include/hw/boards.h
>>> @@ -256,6 +256,7 @@ struct MachineState {
>>>      bool suppress_vmdesc;
>>>      bool enforce_config_section;
>>>      bool enable_graphics;
>>> +    bool split_lock_ac;
>>>      char *memory_encryption;
>>>      DeviceMemoryState *device_memory;
>>>
>>> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
>>> index 98f389a..4bfa879 100644
>>> --- a/linux-headers/linux/kvm.h
>>> +++ b/linux-headers/linux/kvm.h
>>> @@ -949,6 +949,7 @@ struct kvm_ppc_resize_hpt {  #define
>>> KVM_CAP_GET_MSR_FEATURES 153  #define KVM_CAP_HYPERV_EVENTFD
>> 154
>>> #define KVM_CAP_HYPERV_TLBFLUSH 155
>>> +#define KVM_CAP_X86_SPLIT_LOCK_AC 156
>>>
>>>  #ifdef KVM_CAP_IRQ_ROUTING
>>>
>>> diff --git a/qemu-options.hx b/qemu-options.hx index 81b1e99..935cefe
>>> 100644
>>> --- a/qemu-options.hx
>>> +++ b/qemu-options.hx
>>> @@ -44,6 +44,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>>>      "                nvdimm=on|off controls NVDIMM support (default=off)\n"
>>>      "                enforce-config-section=on|off enforce configuration section
>> migration (default=off)\n"
>>>      "                s390-squash-mcss=on|off (deprecated) controls support for
>> squashing into default css (default=off)\n"
>>> +    "                split-lock-ac=on|off controls support #AC exception for split
>> locked accesses (default=off)\n"
>>>      "                memory-encryption=@var{} memory encryption object to use
>> (default=none)\n",
>>>      QEMU_ARCH_ALL)
>>>  STEXI
>>> @@ -113,6 +114,8 @@ NOTE: this parameter is deprecated. Please use
>>> @option{-global}  @option{migration.send-configuration}=@var{on|off}
>> instead.
>>>  @item memory-encryption=@var{}
>>>  Memory encryption object to use. The default is none.
>>> +@item split-lock-ac=on|off
>>> +Enables or disables #AC exception for split locked accesses.
>>>  @end table
>>>  ETEXI
>>>
>>>
>