Instead of using generic CONFIG_HVM option switch to a bit more specific
CONFIG_ALTP2M option for altp2m support. Also guard altp2m routines, so that
they can be disabled completely in the build -- when target platform does not
actually support altp2m (AMD-V & ARM as of now).

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
CC: Tamas K Lengyel <tamas@tklengyel.com>
---
changes in v2:
 - use separate CONFIG_ALTP2M option instead of CONFIG_VMX
---
 xen/arch/x86/include/asm/altp2m.h  |  5 ++++-
 xen/arch/x86/include/asm/hvm/hvm.h |  2 +-
 xen/arch/x86/include/asm/p2m.h     | 17 ++++++++++++++++-
 xen/arch/x86/mm/Makefile           |  2 +-
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/include/asm/altp2m.h b/xen/arch/x86/include/asm/altp2m.h
index e5e59cbd68..092b13e231 100644
--- a/xen/arch/x86/include/asm/altp2m.h
+++ b/xen/arch/x86/include/asm/altp2m.h
@@ -7,7 +7,7 @@
 #ifndef __ASM_X86_ALTP2M_H
 #define __ASM_X86_ALTP2M_H
 
-#ifdef CONFIG_HVM
+#ifdef CONFIG_ALTP2M
 
 #include <xen/types.h>
 #include <xen/sched.h>         /* for struct vcpu, struct domain */
@@ -38,7 +38,10 @@ static inline bool altp2m_active(const struct domain *d)
 }
 
 /* Only declaration is needed. DCE will optimise it out when linking. */
+void altp2m_vcpu_initialise(struct vcpu *v);
+void altp2m_vcpu_destroy(struct vcpu *v);
 uint16_t altp2m_vcpu_idx(const struct vcpu *v);
+int altp2m_vcpu_enable_ve(struct vcpu *v, gfn_t gfn);
 void altp2m_vcpu_disable_ve(struct vcpu *v);
 
 #endif
diff --git a/xen/arch/x86/include/asm/hvm/hvm.h b/xen/arch/x86/include/asm/hvm/hvm.h
index 0c9e6f1564..4f03dd7af8 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -670,7 +670,7 @@ static inline bool hvm_hap_supported(void)
 /* returns true if hardware supports alternate p2m's */
 static inline bool hvm_altp2m_supported(void)
 {
-    return hvm_funcs.caps.altp2m;
+    return IS_ENABLED(CONFIG_ALTP2M) && hvm_funcs.caps.altp2m;
 }
 
 /* Returns true if we have the minimum hardware requirements for nested virt */
diff --git a/xen/arch/x86/include/asm/p2m.h b/xen/arch/x86/include/asm/p2m.h
index 111badf89a..855e69d24a 100644
--- a/xen/arch/x86/include/asm/p2m.h
+++ b/xen/arch/x86/include/asm/p2m.h
@@ -581,9 +581,9 @@ static inline gfn_t mfn_to_gfn(const struct domain *d, mfn_t mfn)
         return _gfn(mfn_x(mfn));
 }
 
-#ifdef CONFIG_HVM
 #define AP2MGET_prepopulate true
 #define AP2MGET_query false
+#ifdef CONFIG_ALTP2M
 
 /*
  * Looks up altp2m entry. If the entry is not found it looks up the entry in
@@ -593,6 +593,15 @@ static inline gfn_t mfn_to_gfn(const struct domain *d, mfn_t mfn)
 int altp2m_get_effective_entry(struct p2m_domain *ap2m, gfn_t gfn, mfn_t *mfn,
                                p2m_type_t *t, p2m_access_t *a,
                                bool prepopulate);
+#else
+static inline int altp2m_get_effective_entry(struct p2m_domain *ap2m,
+                                             gfn_t gfn, mfn_t *mfn,
+                                             p2m_type_t *t, p2m_access_t *a,
+                                             bool prepopulate)
+{
+    ASSERT_UNREACHABLE();
+    return -EOPNOTSUPP;
+}
 #endif
 
 /* Init the datastructures for later use by the p2m code */
@@ -909,8 +918,14 @@ static inline bool p2m_set_altp2m(struct vcpu *v, unsigned int idx)
 /* Switch alternate p2m for a single vcpu */
 bool p2m_switch_vcpu_altp2m_by_id(struct vcpu *v, unsigned int idx);
 
+#ifdef CONFIG_ALTP2M
 /* Check to see if vcpu should be switched to a different p2m. */
 void p2m_altp2m_check(struct vcpu *v, uint16_t idx);
+#else
+static inline void p2m_altp2m_check(struct vcpu *v, uint16_t idx)
+{
+}
+#endif
 
 /* Flush all the alternate p2m's for a domain */
 void p2m_flush_altp2m(struct domain *d);
diff --git a/xen/arch/x86/mm/Makefile b/xen/arch/x86/mm/Makefile
index 0128ca7ab6..d7d57b8190 100644
--- a/xen/arch/x86/mm/Makefile
+++ b/xen/arch/x86/mm/Makefile
@@ -1,7 +1,7 @@
 obj-y += shadow/
 obj-$(CONFIG_HVM) += hap/
 
-obj-$(CONFIG_HVM) += altp2m.o
+obj-$(CONFIG_ALTP2M) += altp2m.o
 obj-$(CONFIG_HVM) += guest_walk_2.o guest_walk_3.o guest_walk_4.o
 obj-$(CONFIG_SHADOW_PAGING) += guest_walk_4.o
 obj-$(CONFIG_MEM_ACCESS) += mem_access.o
-- 
2.25.1

On 15.05.2024 11:10, Sergiy Kibrik wrote:
> @@ -38,7 +38,10 @@ static inline bool altp2m_active(const struct domain *d)
>  }
>  
>  /* Only declaration is needed. DCE will optimise it out when linking. */
> +void altp2m_vcpu_initialise(struct vcpu *v);
> +void altp2m_vcpu_destroy(struct vcpu *v);
>  uint16_t altp2m_vcpu_idx(const struct vcpu *v);
> +int altp2m_vcpu_enable_ve(struct vcpu *v, gfn_t gfn);
>  void altp2m_vcpu_disable_ve(struct vcpu *v);

These additions look unrelated, as long as the description says nothing in
this regard.

> --- a/xen/arch/x86/include/asm/hvm/hvm.h
> +++ b/xen/arch/x86/include/asm/hvm/hvm.h
> @@ -670,7 +670,7 @@ static inline bool hvm_hap_supported(void)
>  /* returns true if hardware supports alternate p2m's */
>  static inline bool hvm_altp2m_supported(void)
>  {
> -    return hvm_funcs.caps.altp2m;
> +    return IS_ENABLED(CONFIG_ALTP2M) && hvm_funcs.caps.altp2m;

Which in turn raises the question whether the altp2m struct field shouldn't
become conditional upon CONFIG_ALTP2M too (or rather: instead, as the change
here then would need to be done differently). Yet maybe that would entail
further changes elsewhere, so may well better be left for later.

> --- a/xen/arch/x86/mm/Makefile
> +++ b/xen/arch/x86/mm/Makefile
> @@ -1,7 +1,7 @@
>  obj-y += shadow/
>  obj-$(CONFIG_HVM) += hap/
>  
> -obj-$(CONFIG_HVM) += altp2m.o
> +obj-$(CONFIG_ALTP2M) += altp2m.o

This change I think wants to move to patch 5.

Jan

16.05.24 14:01, Jan Beulich:
> On 15.05.2024 11:10, Sergiy Kibrik wrote:
>> @@ -38,7 +38,10 @@ static inline bool altp2m_active(const struct domain *d)
>>   }
>>   
>>   /* Only declaration is needed. DCE will optimise it out when linking. */
>> +void altp2m_vcpu_initialise(struct vcpu *v);
>> +void altp2m_vcpu_destroy(struct vcpu *v);
>>   uint16_t altp2m_vcpu_idx(const struct vcpu *v);
>> +int altp2m_vcpu_enable_ve(struct vcpu *v, gfn_t gfn);
>>   void altp2m_vcpu_disable_ve(struct vcpu *v);
> 
> These additions look unrelated, as long as the description says nothing in
> this regard.

agree, I'll update description on why these declarations are added

> 
>> --- a/xen/arch/x86/include/asm/hvm/hvm.h
>> +++ b/xen/arch/x86/include/asm/hvm/hvm.h
>> @@ -670,7 +670,7 @@ static inline bool hvm_hap_supported(void)
>>   /* returns true if hardware supports alternate p2m's */
>>   static inline bool hvm_altp2m_supported(void)
>>   {
>> -    return hvm_funcs.caps.altp2m;
>> +    return IS_ENABLED(CONFIG_ALTP2M) && hvm_funcs.caps.altp2m;
> 
> Which in turn raises the question whether the altp2m struct field shouldn't
> become conditional upon CONFIG_ALTP2M too (or rather: instead, as the change
> here then would need to be done differently). Yet maybe that would entail
> further changes elsewhere, so may well better be left for later.
> 

  but hvm_funcs.caps.altp2m is only a capability bit -- is it worth to 
become conditional?

>> --- a/xen/arch/x86/mm/Makefile
>> +++ b/xen/arch/x86/mm/Makefile
>> @@ -1,7 +1,7 @@
>>   obj-y += shadow/
>>   obj-$(CONFIG_HVM) += hap/
>>   
>> -obj-$(CONFIG_HVM) += altp2m.o
>> +obj-$(CONFIG_ALTP2M) += altp2m.o
> 
> This change I think wants to move to patch 5.
> 

If this moves to patch 5 then HVM=y && ALTP2M=n configuration 
combination will break the build in between patch 5 and 6, so I've 
decided to put it together with fixes of these build failures in patch 6.
Maybe I can merge patch 5 & 6 together then ?

   -Sergiy

On 23.05.2024 12:44, Sergiy Kibrik wrote:
> 16.05.24 14:01, Jan Beulich:
>> On 15.05.2024 11:10, Sergiy Kibrik wrote:
>>> --- a/xen/arch/x86/include/asm/hvm/hvm.h
>>> +++ b/xen/arch/x86/include/asm/hvm/hvm.h
>>> @@ -670,7 +670,7 @@ static inline bool hvm_hap_supported(void)
>>>   /* returns true if hardware supports alternate p2m's */
>>>   static inline bool hvm_altp2m_supported(void)
>>>   {
>>> -    return hvm_funcs.caps.altp2m;
>>> +    return IS_ENABLED(CONFIG_ALTP2M) && hvm_funcs.caps.altp2m;
>>
>> Which in turn raises the question whether the altp2m struct field shouldn't
>> become conditional upon CONFIG_ALTP2M too (or rather: instead, as the change
>> here then would need to be done differently). Yet maybe that would entail
>> further changes elsewhere, so may well better be left for later.
> 
>   but hvm_funcs.caps.altp2m is only a capability bit -- is it worth to 
> become conditional?

Well, the comment was more based on the overall principle than the actual
space savings that might result. Plus as said - likely that would not work
anyway without further changes elsewhere. So perhaps okay to leave as you
have it.

>>> --- a/xen/arch/x86/mm/Makefile
>>> +++ b/xen/arch/x86/mm/Makefile
>>> @@ -1,7 +1,7 @@
>>>   obj-y += shadow/
>>>   obj-$(CONFIG_HVM) += hap/
>>>   
>>> -obj-$(CONFIG_HVM) += altp2m.o
>>> +obj-$(CONFIG_ALTP2M) += altp2m.o
>>
>> This change I think wants to move to patch 5.
>>
> 
> If this moves to patch 5 then HVM=y && ALTP2M=n configuration 
> combination will break the build in between patch 5 and 6, so I've 
> decided to put it together with fixes of these build failures in patch 6.

Hmm, yes, I think I see what you mean.

> Maybe I can merge patch 5 & 6 together then ?

Perhaps more consistent that way, yes.

Jan

On Wed, 15 May 2024, Sergiy Kibrik wrote:
> Instead of using generic CONFIG_HVM option switch to a bit more specific
> CONFIG_ALTP2M option for altp2m support. Also guard altp2m routines, so that
> they can be disabled completely in the build -- when target platform does not
> actually support altp2m (AMD-V & ARM as of now).
> 
> Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
> CC: Tamas K Lengyel <tamas@tklengyel.com>
> ---
> changes in v2:
>  - use separate CONFIG_ALTP2M option instead of CONFIG_VMX
> ---
>  xen/arch/x86/include/asm/altp2m.h  |  5 ++++-
>  xen/arch/x86/include/asm/hvm/hvm.h |  2 +-
>  xen/arch/x86/include/asm/p2m.h     | 17 ++++++++++++++++-
>  xen/arch/x86/mm/Makefile           |  2 +-
>  4 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/include/asm/altp2m.h b/xen/arch/x86/include/asm/altp2m.h
> index e5e59cbd68..092b13e231 100644
> --- a/xen/arch/x86/include/asm/altp2m.h
> +++ b/xen/arch/x86/include/asm/altp2m.h
> @@ -7,7 +7,7 @@
>  #ifndef __ASM_X86_ALTP2M_H
>  #define __ASM_X86_ALTP2M_H
>  
> -#ifdef CONFIG_HVM
> +#ifdef CONFIG_ALTP2M
>  
>  #include <xen/types.h>
>  #include <xen/sched.h>         /* for struct vcpu, struct domain */
> @@ -38,7 +38,10 @@ static inline bool altp2m_active(const struct domain *d)
>  }
>  
>  /* Only declaration is needed. DCE will optimise it out when linking. */
> +void altp2m_vcpu_initialise(struct vcpu *v);
> +void altp2m_vcpu_destroy(struct vcpu *v);
>  uint16_t altp2m_vcpu_idx(const struct vcpu *v);
> +int altp2m_vcpu_enable_ve(struct vcpu *v, gfn_t gfn);
>  void altp2m_vcpu_disable_ve(struct vcpu *v);
>  
>  #endif
> diff --git a/xen/arch/x86/include/asm/hvm/hvm.h b/xen/arch/x86/include/asm/hvm/hvm.h
> index 0c9e6f1564..4f03dd7af8 100644
> --- a/xen/arch/x86/include/asm/hvm/hvm.h
> +++ b/xen/arch/x86/include/asm/hvm/hvm.h
> @@ -670,7 +670,7 @@ static inline bool hvm_hap_supported(void)
>  /* returns true if hardware supports alternate p2m's */
>  static inline bool hvm_altp2m_supported(void)
>  {
> -    return hvm_funcs.caps.altp2m;
> +    return IS_ENABLED(CONFIG_ALTP2M) && hvm_funcs.caps.altp2m;
>  }
>  
>  /* Returns true if we have the minimum hardware requirements for nested virt */
> diff --git a/xen/arch/x86/include/asm/p2m.h b/xen/arch/x86/include/asm/p2m.h
> index 111badf89a..855e69d24a 100644
> --- a/xen/arch/x86/include/asm/p2m.h
> +++ b/xen/arch/x86/include/asm/p2m.h
> @@ -581,9 +581,9 @@ static inline gfn_t mfn_to_gfn(const struct domain *d, mfn_t mfn)
>          return _gfn(mfn_x(mfn));
>  }
>  
> -#ifdef CONFIG_HVM
>  #define AP2MGET_prepopulate true
>  #define AP2MGET_query false
> +#ifdef CONFIG_ALTP2M

Is it necessary? Can't we just replace CONFIG_HVM with CONFIG_ALTP2M on
the same line

On 16.05.2024 02:38, Stefano Stabellini wrote:
> On Wed, 15 May 2024, Sergiy Kibrik wrote:
>> --- a/xen/arch/x86/include/asm/p2m.h
>> +++ b/xen/arch/x86/include/asm/p2m.h
>> @@ -581,9 +581,9 @@ static inline gfn_t mfn_to_gfn(const struct domain *d, mfn_t mfn)
>>          return _gfn(mfn_x(mfn));
>>  }
>>  
>> -#ifdef CONFIG_HVM
>>  #define AP2MGET_prepopulate true
>>  #define AP2MGET_query false
>> +#ifdef CONFIG_ALTP2M
> 
> Is it necessary? Can't we just replace CONFIG_HVM with CONFIG_ALTP2M on
> the same line

No, because of where those constants are used.

Sergiy, you want to move the new #ifdef down by a line though, such that
the #define-s are separated from it by the blank line that presently (with
your change applied) follows the #ifdef line.

Jan