diff mbox series

[XEN,v11,2/8] x86/pvh: Allow (un)map_pirq when dom0 is PVH

Message ID 20240630123344.20623-3-Jiqian.Chen@amd.com (mailing list archive)
State New
Headers show
Series Support device passthrough when dom0 is PVH on Xen | expand

Commit Message

Chen, Jiqian June 30, 2024, 12:33 p.m. UTC
If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
a passthrough device by using gsi, see qemu code
xen_pt_realize->xc_physdev_map_pirq and libxl code
pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
is not allowed because currd is PVH dom0 and PVH has no
X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.

So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
And add a new check to prevent (un)map when the subject domain
has no X86_EMU_USE_PIRQ flag.

So that the interrupt of a passthrough device can be
successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
when dom0 is PVH

Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
---
 xen/arch/x86/hvm/hypercall.c |  6 ++++++
 xen/arch/x86/physdev.c       | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

Comments

Jan Beulich July 1, 2024, 7:44 a.m. UTC | #1
On 30.06.2024 14:33, Jiqian Chen wrote:
> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
> a passthrough device by using gsi, see qemu code
> xen_pt_realize->xc_physdev_map_pirq and libxl code
> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
> is not allowed because currd is PVH dom0 and PVH has no
> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
> 
> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
> PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
> And add a new check to prevent (un)map when the subject domain
> has no X86_EMU_USE_PIRQ flag.
> 
> So that the interrupt of a passthrough device can be
> successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
> when dom0 is PVH
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> Signed-off-by: Huang Rui <ray.huang@amd.com>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

You keep carrying this R-b, despite making functional changes. This can't be
quite right.

While functionally I'm now okay with the change, I still have a code structure
concern:

> --- a/xen/arch/x86/physdev.c
> +++ b/xen/arch/x86/physdev.c
> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>          if ( !d )
>              break;
>  
> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
> +        if ( is_hvm_domain(d) && !has_pirq(d) )
> +        {
> +            rcu_unlock_domain(d);
> +            return -EOPNOTSUPP;
> +        }
> +
>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>  
>          rcu_unlock_domain(d);
> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>          if ( !d )
>              break;
>  
> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
> +        if ( is_hvm_domain(d) && !has_pirq(d) )
> +        {
> +            rcu_unlock_domain(d);
> +            return -EOPNOTSUPP;
> +        }
> +
>          ret = physdev_unmap_pirq(d, unmap.pirq);
>  
>          rcu_unlock_domain(d);

If you did go look, you will have noticed that we use "return" in the middle
of this function only very sparingly (when alternatives would result in more
complicated code elsewhere). I think you want to avoid "return" here, too,
and probably go even further and avoid the extra rcu_unlock_domain() as well.
That's easily possible to arrange for (taking the latter case as example):

        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
        if ( !is_hvm_domain(d) || has_pirq(d) )
            ret = physdev_unmap_pirq(d, unmap.pirq);
        else
            ret = -EOPNOTSUPP;

        rcu_unlock_domain(d);

Personally I would even use a conditional operator here, but I believe
others might dislike its use in situations like this one.

The re-arrangement make a little more noticeable though that the comment
isn't quite right either: PV domains necessarily have no
X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?

Jan
Chen, Jiqian July 2, 2024, 3:15 a.m. UTC | #2
On 2024/7/1 15:44, Jan Beulich wrote:
> On 30.06.2024 14:33, Jiqian Chen wrote:
>> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
>> a passthrough device by using gsi, see qemu code
>> xen_pt_realize->xc_physdev_map_pirq and libxl code
>> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
>> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
>> is not allowed because currd is PVH dom0 and PVH has no
>> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
>>
>> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
>> PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
>> And add a new check to prevent (un)map when the subject domain
>> has no X86_EMU_USE_PIRQ flag.
>>
>> So that the interrupt of a passthrough device can be
>> successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
>> when dom0 is PVH
>>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>> Signed-off-by: Huang Rui <ray.huang@amd.com>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> 
> You keep carrying this R-b, despite making functional changes. This can't be
> quite right.
Will remove in next version.

> 
> While functionally I'm now okay with the change, I still have a code structure
> concern:
> 
>> --- a/xen/arch/x86/physdev.c
>> +++ b/xen/arch/x86/physdev.c
>> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>          if ( !d )
>>              break;
>>  
>> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>> +        {
>> +            rcu_unlock_domain(d);
>> +            return -EOPNOTSUPP;
>> +        }
>> +
>>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>>  
>>          rcu_unlock_domain(d);
>> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>          if ( !d )
>>              break;
>>  
>> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>> +        {
>> +            rcu_unlock_domain(d);
>> +            return -EOPNOTSUPP;
>> +        }
>> +
>>          ret = physdev_unmap_pirq(d, unmap.pirq);
>>  
>>          rcu_unlock_domain(d);
> 
> If you did go look, you will have noticed that we use "return" in the middle
> of this function only very sparingly (when alternatives would result in more
> complicated code elsewhere). I think you want to avoid "return" here, too,
> and probably go even further and avoid the extra rcu_unlock_domain() as well.
> That's easily possible to arrange for (taking the latter case as example):
> 
>         /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>         if ( !is_hvm_domain(d) || has_pirq(d) )
>             ret = physdev_unmap_pirq(d, unmap.pirq);
>         else
>             ret = -EOPNOTSUPP;
> 
>         rcu_unlock_domain(d);
> 
> Personally I would even use a conditional operator here, but I believe
> others might dislike its use in situations like this one.
> 
> The re-arrangement make a little more noticeable though that the comment
> isn't quite right either: PV domains necessarily have no
> X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?

Or just like below?

        /*
         * Prevent unmapping when the subject hvm domain has no
         * X86_EMU_USE_PIRQ
         */
        if ( is_hvm_domain(d) && !has_pirq(d) )
            ret = -EOPNOTSUPP;
        else
            ret = physdev_unmap_pirq(d, unmap.pirq);

> 
> Jan
Jan Beulich July 2, 2024, 8:44 a.m. UTC | #3
On 02.07.2024 05:15, Chen, Jiqian wrote:
> On 2024/7/1 15:44, Jan Beulich wrote:
>> On 30.06.2024 14:33, Jiqian Chen wrote:
>>> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
>>> a passthrough device by using gsi, see qemu code
>>> xen_pt_realize->xc_physdev_map_pirq and libxl code
>>> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
>>> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
>>> is not allowed because currd is PVH dom0 and PVH has no
>>> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
>>>
>>> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
>>> PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
>>> And add a new check to prevent (un)map when the subject domain
>>> has no X86_EMU_USE_PIRQ flag.
>>>
>>> So that the interrupt of a passthrough device can be
>>> successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
>>> when dom0 is PVH
>>>
>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>> Signed-off-by: Huang Rui <ray.huang@amd.com>
>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
>>
>> You keep carrying this R-b, despite making functional changes. This can't be
>> quite right.
> Will remove in next version.
> 
>>
>> While functionally I'm now okay with the change, I still have a code structure
>> concern:
>>
>>> --- a/xen/arch/x86/physdev.c
>>> +++ b/xen/arch/x86/physdev.c
>>> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>          if ( !d )
>>>              break;
>>>  
>>> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>> +        {
>>> +            rcu_unlock_domain(d);
>>> +            return -EOPNOTSUPP;
>>> +        }
>>> +
>>>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>>>  
>>>          rcu_unlock_domain(d);
>>> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>          if ( !d )
>>>              break;
>>>  
>>> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>> +        {
>>> +            rcu_unlock_domain(d);
>>> +            return -EOPNOTSUPP;
>>> +        }
>>> +
>>>          ret = physdev_unmap_pirq(d, unmap.pirq);
>>>  
>>>          rcu_unlock_domain(d);
>>
>> If you did go look, you will have noticed that we use "return" in the middle
>> of this function only very sparingly (when alternatives would result in more
>> complicated code elsewhere). I think you want to avoid "return" here, too,
>> and probably go even further and avoid the extra rcu_unlock_domain() as well.
>> That's easily possible to arrange for (taking the latter case as example):
>>
>>         /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>         if ( !is_hvm_domain(d) || has_pirq(d) )
>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>         else
>>             ret = -EOPNOTSUPP;
>>
>>         rcu_unlock_domain(d);
>>
>> Personally I would even use a conditional operator here, but I believe
>> others might dislike its use in situations like this one.
>>
>> The re-arrangement make a little more noticeable though that the comment
>> isn't quite right either: PV domains necessarily have no
>> X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?
> 
> Or just like below?
> 
>         /*
>          * Prevent unmapping when the subject hvm domain has no
>          * X86_EMU_USE_PIRQ
>          */
>         if ( is_hvm_domain(d) && !has_pirq(d) )
>             ret = -EOPNOTSUPP;
>         else
>             ret = physdev_unmap_pirq(d, unmap.pirq);

No objection to the slightly changed comment. The code alternative you
present is of course functionally identical, yet personally I prefer to
have the "good" case on the "if" branch and the "bad" one following
"else". I wouldn't insist, though.

Jan
Chen, Jiqian July 4, 2024, 2:56 a.m. UTC | #4
On 2024/7/2 16:44, Jan Beulich wrote:
> On 02.07.2024 05:15, Chen, Jiqian wrote:
>> On 2024/7/1 15:44, Jan Beulich wrote:
>>> On 30.06.2024 14:33, Jiqian Chen wrote:
>>>> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
>>>> a passthrough device by using gsi, see qemu code
>>>> xen_pt_realize->xc_physdev_map_pirq and libxl code
>>>> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
>>>> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
>>>> is not allowed because currd is PVH dom0 and PVH has no
>>>> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
>>>>
>>>> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
>>>> PHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
>>>> And add a new check to prevent (un)map when the subject domain
>>>> has no X86_EMU_USE_PIRQ flag.
>>>>
>>>> So that the interrupt of a passthrough device can be
>>>> successfully mapped to pirq for domU with X86_EMU_USE_PIRQ flag
>>>> when dom0 is PVH
>>>>
>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>>> Signed-off-by: Huang Rui <ray.huang@amd.com>
>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>>> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
>>>
>>> You keep carrying this R-b, despite making functional changes. This can't be
>>> quite right.
>> Will remove in next version.
>>
>>>
>>> While functionally I'm now okay with the change, I still have a code structure
>>> concern:
>>>
>>>> --- a/xen/arch/x86/physdev.c
>>>> +++ b/xen/arch/x86/physdev.c
>>>> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>          if ( !d )
>>>>              break;
>>>>  
>>>> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>> +        {
>>>> +            rcu_unlock_domain(d);
>>>> +            return -EOPNOTSUPP;
>>>> +        }
>>>> +
>>>>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>>>>  
>>>>          rcu_unlock_domain(d);
>>>> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>          if ( !d )
>>>>              break;
>>>>  
>>>> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>> +        {
>>>> +            rcu_unlock_domain(d);
>>>> +            return -EOPNOTSUPP;
>>>> +        }
>>>> +
>>>>          ret = physdev_unmap_pirq(d, unmap.pirq);
>>>>  
>>>>          rcu_unlock_domain(d);
>>>
>>> If you did go look, you will have noticed that we use "return" in the middle
>>> of this function only very sparingly (when alternatives would result in more
>>> complicated code elsewhere). I think you want to avoid "return" here, too,
>>> and probably go even further and avoid the extra rcu_unlock_domain() as well.
>>> That's easily possible to arrange for (taking the latter case as example):
>>>
>>>         /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>         if ( !is_hvm_domain(d) || has_pirq(d) )
>>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>>         else
>>>             ret = -EOPNOTSUPP;
>>>
>>>         rcu_unlock_domain(d);
>>>
>>> Personally I would even use a conditional operator here, but I believe
>>> others might dislike its use in situations like this one.
>>>
>>> The re-arrangement make a little more noticeable though that the comment
>>> isn't quite right either: PV domains necessarily have no
>>> X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?
>>
>> Or just like below?
>>
>>         /*
>>          * Prevent unmapping when the subject hvm domain has no
>>          * X86_EMU_USE_PIRQ
>>          */
>>         if ( is_hvm_domain(d) && !has_pirq(d) )
>>             ret = -EOPNOTSUPP;
>>         else
>>             ret = physdev_unmap_pirq(d, unmap.pirq);
> 
> No objection to the slightly changed comment. The code alternative you
> present is of course functionally identical, yet personally I prefer to
> have the "good" case on the "if" branch and the "bad" one following
> "else". I wouldn't insist, though.
OK, will change "good" case on the "if" branch.
Do I need to change "!is_hvm_domain(d)" to "is_pv_domain(d)" ?
And then have:

        /* Only unmapping when the subject domain has a notion of PIRQ */
        if ( is_pv_domain(d) || has_pirq(d) )
            ret = physdev_unmap_pirq(d, unmap.pirq);
        else
            ret = -EOPNOTSUPP;

> 
> Jan
Jan Beulich July 4, 2024, 6:38 a.m. UTC | #5
On 04.07.2024 04:56, Chen, Jiqian wrote:
> On 2024/7/2 16:44, Jan Beulich wrote:
>> On 02.07.2024 05:15, Chen, Jiqian wrote:
>>> On 2024/7/1 15:44, Jan Beulich wrote:
>>>> On 30.06.2024 14:33, Jiqian Chen wrote:
>>>>> --- a/xen/arch/x86/physdev.c
>>>>> +++ b/xen/arch/x86/physdev.c
>>>>> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>>          if ( !d )
>>>>>              break;
>>>>>  
>>>>> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>>> +        {
>>>>> +            rcu_unlock_domain(d);
>>>>> +            return -EOPNOTSUPP;
>>>>> +        }
>>>>> +
>>>>>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>>>>>  
>>>>>          rcu_unlock_domain(d);
>>>>> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>>          if ( !d )
>>>>>              break;
>>>>>  
>>>>> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>>> +        {
>>>>> +            rcu_unlock_domain(d);
>>>>> +            return -EOPNOTSUPP;
>>>>> +        }
>>>>> +
>>>>>          ret = physdev_unmap_pirq(d, unmap.pirq);
>>>>>  
>>>>>          rcu_unlock_domain(d);
>>>>
>>>> If you did go look, you will have noticed that we use "return" in the middle
>>>> of this function only very sparingly (when alternatives would result in more
>>>> complicated code elsewhere). I think you want to avoid "return" here, too,
>>>> and probably go even further and avoid the extra rcu_unlock_domain() as well.
>>>> That's easily possible to arrange for (taking the latter case as example):
>>>>
>>>>         /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>         if ( !is_hvm_domain(d) || has_pirq(d) )
>>>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>>>         else
>>>>             ret = -EOPNOTSUPP;
>>>>
>>>>         rcu_unlock_domain(d);
>>>>
>>>> Personally I would even use a conditional operator here, but I believe
>>>> others might dislike its use in situations like this one.
>>>>
>>>> The re-arrangement make a little more noticeable though that the comment
>>>> isn't quite right either: PV domains necessarily have no
>>>> X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?
>>>
>>> Or just like below?
>>>
>>>         /*
>>>          * Prevent unmapping when the subject hvm domain has no
>>>          * X86_EMU_USE_PIRQ
>>>          */
>>>         if ( is_hvm_domain(d) && !has_pirq(d) )
>>>             ret = -EOPNOTSUPP;
>>>         else
>>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>
>> No objection to the slightly changed comment. The code alternative you
>> present is of course functionally identical, yet personally I prefer to
>> have the "good" case on the "if" branch and the "bad" one following
>> "else". I wouldn't insist, though.
> OK, will change "good" case on the "if" branch.
> Do I need to change "!is_hvm_domain(d)" to "is_pv_domain(d)" ?
> And then have:
> 
>         /* Only unmapping when the subject domain has a notion of PIRQ */
>         if ( is_pv_domain(d) || has_pirq(d) )
>             ret = physdev_unmap_pirq(d, unmap.pirq);
>         else
>             ret = -EOPNOTSUPP;

I for one would prefer if you kept using is_hvm_domain(), for being more
precise in this situation.

Jan
Chen, Jiqian July 4, 2024, 6:51 a.m. UTC | #6
On 2024/7/4 14:38, Jan Beulich wrote:
> On 04.07.2024 04:56, Chen, Jiqian wrote:
>> On 2024/7/2 16:44, Jan Beulich wrote:
>>> On 02.07.2024 05:15, Chen, Jiqian wrote:
>>>> On 2024/7/1 15:44, Jan Beulich wrote:
>>>>> On 30.06.2024 14:33, Jiqian Chen wrote:
>>>>>> --- a/xen/arch/x86/physdev.c
>>>>>> +++ b/xen/arch/x86/physdev.c
>>>>>> @@ -323,6 +323,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>>>          if ( !d )
>>>>>>              break;
>>>>>>  
>>>>>> +        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>>>> +        {
>>>>>> +            rcu_unlock_domain(d);
>>>>>> +            return -EOPNOTSUPP;
>>>>>> +        }
>>>>>> +
>>>>>>          ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
>>>>>>  
>>>>>>          rcu_unlock_domain(d);
>>>>>> @@ -346,6 +353,13 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>>>          if ( !d )
>>>>>>              break;
>>>>>>  
>>>>>> +        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>>> +        if ( is_hvm_domain(d) && !has_pirq(d) )
>>>>>> +        {
>>>>>> +            rcu_unlock_domain(d);
>>>>>> +            return -EOPNOTSUPP;
>>>>>> +        }
>>>>>> +
>>>>>>          ret = physdev_unmap_pirq(d, unmap.pirq);
>>>>>>  
>>>>>>          rcu_unlock_domain(d);
>>>>>
>>>>> If you did go look, you will have noticed that we use "return" in the middle
>>>>> of this function only very sparingly (when alternatives would result in more
>>>>> complicated code elsewhere). I think you want to avoid "return" here, too,
>>>>> and probably go even further and avoid the extra rcu_unlock_domain() as well.
>>>>> That's easily possible to arrange for (taking the latter case as example):
>>>>>
>>>>>         /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
>>>>>         if ( !is_hvm_domain(d) || has_pirq(d) )
>>>>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>>>>         else
>>>>>             ret = -EOPNOTSUPP;
>>>>>
>>>>>         rcu_unlock_domain(d);
>>>>>
>>>>> Personally I would even use a conditional operator here, but I believe
>>>>> others might dislike its use in situations like this one.
>>>>>
>>>>> The re-arrangement make a little more noticeable though that the comment
>>>>> isn't quite right either: PV domains necessarily have no
>>>>> X86_EMU_USE_PIRQ. Maybe "... has no notion of pIRQ"?
>>>>
>>>> Or just like below?
>>>>
>>>>         /*
>>>>          * Prevent unmapping when the subject hvm domain has no
>>>>          * X86_EMU_USE_PIRQ
>>>>          */
>>>>         if ( is_hvm_domain(d) && !has_pirq(d) )
>>>>             ret = -EOPNOTSUPP;
>>>>         else
>>>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>>
>>> No objection to the slightly changed comment. The code alternative you
>>> present is of course functionally identical, yet personally I prefer to
>>> have the "good" case on the "if" branch and the "bad" one following
>>> "else". I wouldn't insist, though.
>> OK, will change "good" case on the "if" branch.
>> Do I need to change "!is_hvm_domain(d)" to "is_pv_domain(d)" ?
>> And then have:
>>
>>         /* Only unmapping when the subject domain has a notion of PIRQ */
>>         if ( is_pv_domain(d) || has_pirq(d) )
>>             ret = physdev_unmap_pirq(d, unmap.pirq);
>>         else
>>             ret = -EOPNOTSUPP;
> 
> I for one would prefer if you kept using is_hvm_domain(), for being more
> precise in this situation.
OK, thanks. Will change in next version.

> 
> Jan
diff mbox series

Patch

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 0fab670a4871..03ada3c880bd 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -71,8 +71,14 @@  long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
 
     switch ( cmd )
     {
+        /*
+        * Only being permitted for management of other domains.
+        * Further restrictions are enforced in do_physdev_op.
+        */
     case PHYSDEVOP_map_pirq:
     case PHYSDEVOP_unmap_pirq:
+        break;
+
     case PHYSDEVOP_eoi:
     case PHYSDEVOP_irq_status_query:
     case PHYSDEVOP_get_free_pirq:
diff --git a/xen/arch/x86/physdev.c b/xen/arch/x86/physdev.c
index d6dd622952a9..a165f68225c1 100644
--- a/xen/arch/x86/physdev.c
+++ b/xen/arch/x86/physdev.c
@@ -323,6 +323,13 @@  ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( !d )
             break;
 
+        /* Prevent mapping when the subject domain has no X86_EMU_USE_PIRQ */
+        if ( is_hvm_domain(d) && !has_pirq(d) )
+        {
+            rcu_unlock_domain(d);
+            return -EOPNOTSUPP;
+        }
+
         ret = physdev_map_pirq(d, map.type, &map.index, &map.pirq, &msi);
 
         rcu_unlock_domain(d);
@@ -346,6 +353,13 @@  ret_t do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( !d )
             break;
 
+        /* Prevent unmapping when the subject domain has no X86_EMU_USE_PIRQ */
+        if ( is_hvm_domain(d) && !has_pirq(d) )
+        {
+            rcu_unlock_domain(d);
+            return -EOPNOTSUPP;
+        }
+
         ret = physdev_unmap_pirq(d, unmap.pirq);
 
         rcu_unlock_domain(d);