[PATCH] VT-d: avoid multi-message-MSI check for HPET

[PATCH] VT-d: avoid multi-message-MSI check for HPET

[Jan Beulich]

Having this immediately below a PCI-dev vs HPET conditional is (mildly)
confusing. Move that if() into the body of the earlier one.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -513,13 +513,13 @@ static int msi_msg_to_remap_entry(
 
         if ( rc )
             return rc;
+
+        if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
+            nr = msi_desc->msi.nvec;
     }
     else
         set_hpet_source_id(msi_desc->hpet_id, &new_ire);
 
-    if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
-        nr = msi_desc->msi.nvec;
-
     spin_lock_irqsave(&iommu->intremap.lock, flags);
 
     if ( msg == NULL )

Re: [PATCH] VT-d: avoid multi-message-MSI check for HPET

[Roger Pau Monné]

On Wed, Apr 01, 2026 at 02:47:48PM +0200, Jan Beulich wrote:
> Having this immediately below a PCI-dev vs HPET conditional is (mildly)
> confusing. Move that if() into the body of the earlier one.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> 
> --- a/xen/drivers/passthrough/vtd/intremap.c
> +++ b/xen/drivers/passthrough/vtd/intremap.c
> @@ -513,13 +513,13 @@ static int msi_msg_to_remap_entry(
>  
>          if ( rc )
>              return rc;
> +
> +        if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
> +            nr = msi_desc->msi.nvec;
>      }
>      else
>          set_hpet_source_id(msi_desc->hpet_id, &new_ire);
>  
> -    if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
> -        nr = msi_desc->msi.nvec;
> -

I'm not fully opposed to this, but maybe it would be good to add a
small comment to note that HPET never use multi-vector MSI?

Thanks, Roger.

Re: [PATCH] VT-d: avoid multi-message-MSI check for HPET

[Jan Beulich]

On 09.04.2026 19:36, Roger Pau Monné wrote:
> On Wed, Apr 01, 2026 at 02:47:48PM +0200, Jan Beulich wrote:
>> Having this immediately below a PCI-dev vs HPET conditional is (mildly)
>> confusing. Move that if() into the body of the earlier one.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>
>> --- a/xen/drivers/passthrough/vtd/intremap.c
>> +++ b/xen/drivers/passthrough/vtd/intremap.c
>> @@ -513,13 +513,13 @@ static int msi_msg_to_remap_entry(
>>  
>>          if ( rc )
>>              return rc;
>> +
>> +        if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
>> +            nr = msi_desc->msi.nvec;
>>      }
>>      else
>>          set_hpet_source_id(msi_desc->hpet_id, &new_ire);
>>  
>> -    if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
>> -        nr = msi_desc->msi.nvec;
>> -
> 
> I'm not fully opposed to this, but maybe it would be good to add a
> small comment to note that HPET never use multi-vector MSI?

That aspect doesn't change - HPET code simply doesn't (and never should)
set .type to PCI_CAP_ID_MSI. That field should reflect reality (and HPET,
iirc, simply leaves it at 0).

Jan

Re: [PATCH] VT-d: avoid multi-message-MSI check for HPET

[Roger Pau Monné]

On Fri, Apr 10, 2026 at 07:51:45AM +0200, Jan Beulich wrote:
> On 09.04.2026 19:36, Roger Pau Monné wrote:
> > On Wed, Apr 01, 2026 at 02:47:48PM +0200, Jan Beulich wrote:
> >> Having this immediately below a PCI-dev vs HPET conditional is (mildly)
> >> confusing. Move that if() into the body of the earlier one.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> >>
> >> --- a/xen/drivers/passthrough/vtd/intremap.c
> >> +++ b/xen/drivers/passthrough/vtd/intremap.c
> >> @@ -513,13 +513,13 @@ static int msi_msg_to_remap_entry(
> >>  
> >>          if ( rc )
> >>              return rc;
> >> +
> >> +        if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
> >> +            nr = msi_desc->msi.nvec;
> >>      }
> >>      else
> >>          set_hpet_source_id(msi_desc->hpet_id, &new_ire);
> >>  
> >> -    if ( msi_desc->msi_attrib.type == PCI_CAP_ID_MSI )
> >> -        nr = msi_desc->msi.nvec;
> >> -
> > 
> > I'm not fully opposed to this, but maybe it would be good to add a
> > small comment to note that HPET never use multi-vector MSI?
> 
> That aspect doesn't change - HPET code simply doesn't (and never should)
> set .type to PCI_CAP_ID_MSI. That field should reflect reality (and HPET,
> iirc, simply leaves it at 0).

Hm, I see, HPET is a very special case which have been "adjusted" to
fit the MSI generation logic.

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.