[PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[Stewart Hildebrand]

A hotplugged PCI device may be added uninitialized. In particular,
memory decoding might be disabled and the BARs might be zeroed. In this
case, the BARs will not be mapped in p2m. However, vpci_make_msix_hole()
unconditionally attempts to punch holes in p2m, leading to init_msix()
failing:

(XEN) d0v0 0000:01:00.0: existing mapping (mfn: 1c1880 type: 0) at 0 clobbers MSIX MMIO area
(XEN) d0 0000:01:00.0: init legacy cap 17 fail rc=-17, mask it

vpci_make_msix_hole() should only attempt to punch holes if the BARs
containing the MSI-X/PBA tables are mapped in p2m. Introduce a helper
for checking if a BAR is enabled, and add a check for the situation
inside vpci_make_msix_hole().

Move the vpci_make_msix_hole() call within modify_decoding() to after
setting ->enabled.

Fixes: ee2eb6849d50 ("vpci: Refactor REGISTER_VPCI_INIT")
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
---
Pipeline: https://gitlab.com/xen-project/people/stewarthildebrand/xen/-/pipelines/2344925375

v1->v2:
* new title, was ("vpci/msix: conditionally invoke vpci_make_msix_hole")
* move BAR enabled check to inside vpci_make_msix_hole()
* introduce vmsix_table_bar_valid() helper
* move vpci_make_msix_hole() call within modify_decoding() to after
  setting ->enabled
* split typo fixup to separate patch

v1: https://lore.kernel.org/xen-devel/20250812151744.460953-1-stewart.hildebrand@amd.com/T/#t
---
 xen/drivers/vpci/header.c | 26 +++++++++++++-------------
 xen/drivers/vpci/msix.c   |  4 ++++
 xen/include/xen/vpci.h    |  6 ++++++
 3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 739a5f610e91..6a28e07a625b 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -122,19 +122,6 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
     bool map = cmd & PCI_COMMAND_MEMORY;
     unsigned int i;
 
-    /*
-     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
-     * can be trapped (and emulated) by Xen when the memory decoding bit is
-     * enabled.
-     *
-     * FIXME: punching holes after the p2m has been set up might be racy for
-     * DomU usage, needs to be revisited.
-     */
-#ifdef CONFIG_HAS_PCI_MSI
-    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
-        return;
-#endif
-
     for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
     {
         struct vpci_bar *bar = &header->bars[i];
@@ -164,6 +151,19 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
             bar->enabled = map;
     }
 
+    /*
+     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
+     * can be trapped (and emulated) by Xen when the memory decoding bit is
+     * enabled.
+     *
+     * FIXME: punching holes after the p2m has been set up might be racy for
+     * DomU usage, needs to be revisited.
+     */
+#ifdef CONFIG_HAS_PCI_MSI
+    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
+        return;
+#endif
+
     if ( !rom_only )
     {
         pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
index 516282205a53..142cfbae59d5 100644
--- a/xen/drivers/vpci/msix.c
+++ b/xen/drivers/vpci/msix.c
@@ -598,6 +598,10 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
     if ( !pdev->vpci->msix )
         return 0;
 
+    if ( !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_TABLE) &&
+         !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_PBA) )
+        return 0;
+
     /* Make sure there's a hole for the MSIX table/PBA in the p2m. */
     for ( i = 0; i < ARRAY_SIZE(pdev->vpci->msix->tables); i++ )
     {
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index d6310104ea17..8ce730791080 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -267,6 +267,12 @@ static inline paddr_t vmsix_table_addr(const struct vpci *vpci, unsigned int nr)
            (vpci->msix->tables[nr] & ~PCI_MSIX_BIRMASK);
 }
 
+static inline bool vmsix_table_bar_valid(const struct vpci *vpci,
+                                         unsigned int nr)
+{
+    return vpci->header.bars[vpci->msix->tables[nr] & PCI_MSIX_BIRMASK].enabled;
+}
+
 /*
  * Note regarding the size calculation of the PBA: the spec mentions "The last
  * QWORD will not necessarily be fully populated", so it implies that the PBA

base-commit: 5eb84d6c992cf4e81936872c441b649057947442
-- 
2.53.0

Re: [PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[Jan Beulich]

On 24.02.2026 03:56, Stewart Hildebrand wrote:
> A hotplugged PCI device may be added uninitialized. In particular,
> memory decoding might be disabled and the BARs might be zeroed. In this
> case, the BARs will not be mapped in p2m. However, vpci_make_msix_hole()
> unconditionally attempts to punch holes in p2m, leading to init_msix()
> failing:
> 
> (XEN) d0v0 0000:01:00.0: existing mapping (mfn: 1c1880 type: 0) at 0 clobbers MSIX MMIO area
> (XEN) d0 0000:01:00.0: init legacy cap 17 fail rc=-17, mask it
> 
> vpci_make_msix_hole() should only attempt to punch holes if the BARs
> containing the MSI-X/PBA tables are mapped in p2m. Introduce a helper
> for checking if a BAR is enabled, and add a check for the situation
> inside vpci_make_msix_hole().
> 
> Move the vpci_make_msix_hole() call within modify_decoding() to after
> setting ->enabled.
> 
> Fixes: ee2eb6849d50 ("vpci: Refactor REGISTER_VPCI_INIT")
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
> ---
> Pipeline: https://gitlab.com/xen-project/people/stewarthildebrand/xen/-/pipelines/2344925375
> 
> v1->v2:
> * new title, was ("vpci/msix: conditionally invoke vpci_make_msix_hole")
> * move BAR enabled check to inside vpci_make_msix_hole()
> * introduce vmsix_table_bar_valid() helper
> * move vpci_make_msix_hole() call within modify_decoding() to after
>   setting ->enabled
> * split typo fixup to separate patch
> 
> v1: https://lore.kernel.org/xen-devel/20250812151744.460953-1-stewart.hildebrand@amd.com/T/#t
> ---
>  xen/drivers/vpci/header.c | 26 +++++++++++++-------------
>  xen/drivers/vpci/msix.c   |  4 ++++
>  xen/include/xen/vpci.h    |  6 ++++++
>  3 files changed, 23 insertions(+), 13 deletions(-)
> 
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index 739a5f610e91..6a28e07a625b 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -122,19 +122,6 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>      bool map = cmd & PCI_COMMAND_MEMORY;
>      unsigned int i;
>  
> -    /*
> -     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
> -     * can be trapped (and emulated) by Xen when the memory decoding bit is
> -     * enabled.
> -     *
> -     * FIXME: punching holes after the p2m has been set up might be racy for
> -     * DomU usage, needs to be revisited.
> -     */
> -#ifdef CONFIG_HAS_PCI_MSI
> -    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
> -        return;
> -#endif
> -
>      for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
>      {
>          struct vpci_bar *bar = &header->bars[i];
> @@ -164,6 +151,19 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>              bar->enabled = map;
>      }
>  
> +    /*
> +     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
> +     * can be trapped (and emulated) by Xen when the memory decoding bit is
> +     * enabled.
> +     *
> +     * FIXME: punching holes after the p2m has been set up might be racy for
> +     * DomU usage, needs to be revisited.
> +     */
> +#ifdef CONFIG_HAS_PCI_MSI
> +    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
> +        return;
> +#endif
> +
>      if ( !rom_only )
>      {
>          pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
> diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
> index 516282205a53..142cfbae59d5 100644
> --- a/xen/drivers/vpci/msix.c
> +++ b/xen/drivers/vpci/msix.c
> @@ -598,6 +598,10 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
>      if ( !pdev->vpci->msix )
>          return 0;
>  
> +    if ( !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_TABLE) &&
> +         !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_PBA) )
> +        return 0;

What if one is enabled and the other isn't? Doesn't the check need to move ...

>      /* Make sure there's a hole for the MSIX table/PBA in the p2m. */
>      for ( i = 0; i < ARRAY_SIZE(pdev->vpci->msix->tables); i++ )
>      {

... into the loop, and then apparently also need mirroring in the hwdom-only
loop further down?

Jan

Re: [PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[Roger Pau Monné]

On Mon, Feb 23, 2026 at 09:56:24PM -0500, Stewart Hildebrand wrote:
> A hotplugged PCI device may be added uninitialized. In particular,
> memory decoding might be disabled and the BARs might be zeroed. In this
> case, the BARs will not be mapped in p2m. However, vpci_make_msix_hole()
> unconditionally attempts to punch holes in p2m, leading to init_msix()
> failing:
> 
> (XEN) d0v0 0000:01:00.0: existing mapping (mfn: 1c1880 type: 0) at 0 clobbers MSIX MMIO area
> (XEN) d0 0000:01:00.0: init legacy cap 17 fail rc=-17, mask it
> 
> vpci_make_msix_hole() should only attempt to punch holes if the BARs
> containing the MSI-X/PBA tables are mapped in p2m. Introduce a helper
> for checking if a BAR is enabled, and add a check for the situation
> inside vpci_make_msix_hole().
> 
> Move the vpci_make_msix_hole() call within modify_decoding() to after
> setting ->enabled.

I would maybe make it clear that the movement of the
vpci_make_msix_hole() call in modify_decoding() is due to the extra
requirement added in this patch that ->enabled must be set before
calling the function.

"As a result of the newly introduced checks in vpci_make_msix_hole(),
move the ..."

Or something along the lines.

> 
> Fixes: ee2eb6849d50 ("vpci: Refactor REGISTER_VPCI_INIT")
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
> ---
> Pipeline: https://gitlab.com/xen-project/people/stewarthildebrand/xen/-/pipelines/2344925375
> 
> v1->v2:
> * new title, was ("vpci/msix: conditionally invoke vpci_make_msix_hole")
> * move BAR enabled check to inside vpci_make_msix_hole()
> * introduce vmsix_table_bar_valid() helper
> * move vpci_make_msix_hole() call within modify_decoding() to after
>   setting ->enabled
> * split typo fixup to separate patch
> 
> v1: https://lore.kernel.org/xen-devel/20250812151744.460953-1-stewart.hildebrand@amd.com/T/#t
> ---
>  xen/drivers/vpci/header.c | 26 +++++++++++++-------------
>  xen/drivers/vpci/msix.c   |  4 ++++
>  xen/include/xen/vpci.h    |  6 ++++++
>  3 files changed, 23 insertions(+), 13 deletions(-)
> 
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index 739a5f610e91..6a28e07a625b 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -122,19 +122,6 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>      bool map = cmd & PCI_COMMAND_MEMORY;
>      unsigned int i;
>  
> -    /*
> -     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
> -     * can be trapped (and emulated) by Xen when the memory decoding bit is
> -     * enabled.
> -     *
> -     * FIXME: punching holes after the p2m has been set up might be racy for
> -     * DomU usage, needs to be revisited.
> -     */
> -#ifdef CONFIG_HAS_PCI_MSI
> -    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
> -        return;
> -#endif
> -
>      for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
>      {
>          struct vpci_bar *bar = &header->bars[i];
> @@ -164,6 +151,19 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>              bar->enabled = map;
>      }
>  
> +    /*
> +     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
> +     * can be trapped (and emulated) by Xen when the memory decoding bit is
> +     * enabled.
> +     *
> +     * FIXME: punching holes after the p2m has been set up might be racy for
> +     * DomU usage, needs to be revisited.
> +     */
> +#ifdef CONFIG_HAS_PCI_MSI
> +    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
> +        return;
> +#endif
> +
>      if ( !rom_only )
>      {
>          pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
> diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
> index 516282205a53..142cfbae59d5 100644
> --- a/xen/drivers/vpci/msix.c
> +++ b/xen/drivers/vpci/msix.c
> @@ -598,6 +598,10 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
>      if ( !pdev->vpci->msix )
>          return 0;
>  
> +    if ( !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_TABLE) &&
> +         !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_PBA) )
> +        return 0;

As Jan pointed out, this needs to be moved inside the loop.

Thanks, Roger.

Re: [PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[Stewart Hildebrand]

On 2/24/26 02:34, Jan Beulich wrote:
> On 24.02.2026 03:56, Stewart Hildebrand wrote:
>> A hotplugged PCI device may be added uninitialized. In particular,
>> memory decoding might be disabled and the BARs might be zeroed. In this
>> case, the BARs will not be mapped in p2m. However, vpci_make_msix_hole()
>> unconditionally attempts to punch holes in p2m, leading to init_msix()
>> failing:
>>
>> (XEN) d0v0 0000:01:00.0: existing mapping (mfn: 1c1880 type: 0) at 0 clobbers MSIX MMIO area
>> (XEN) d0 0000:01:00.0: init legacy cap 17 fail rc=-17, mask it
>>
>> vpci_make_msix_hole() should only attempt to punch holes if the BARs
>> containing the MSI-X/PBA tables are mapped in p2m. Introduce a helper
>> for checking if a BAR is enabled, and add a check for the situation
>> inside vpci_make_msix_hole().
>>
>> Move the vpci_make_msix_hole() call within modify_decoding() to after
>> setting ->enabled.
>>
>> Fixes: ee2eb6849d50 ("vpci: Refactor REGISTER_VPCI_INIT")
>> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
>> ---
>> Pipeline: https://gitlab.com/xen-project/people/stewarthildebrand/xen/-/pipelines/2344925375
>>
>> v1->v2:
>> * new title, was ("vpci/msix: conditionally invoke vpci_make_msix_hole")
>> * move BAR enabled check to inside vpci_make_msix_hole()
>> * introduce vmsix_table_bar_valid() helper
>> * move vpci_make_msix_hole() call within modify_decoding() to after
>>   setting ->enabled
>> * split typo fixup to separate patch
>>
>> v1: https://lore.kernel.org/xen-devel/20250812151744.460953-1-stewart.hildebrand@amd.com/T/#t
>> ---
>>  xen/drivers/vpci/header.c | 26 +++++++++++++-------------
>>  xen/drivers/vpci/msix.c   |  4 ++++
>>  xen/include/xen/vpci.h    |  6 ++++++
>>  3 files changed, 23 insertions(+), 13 deletions(-)
>>
>> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
>> index 739a5f610e91..6a28e07a625b 100644
>> --- a/xen/drivers/vpci/header.c
>> +++ b/xen/drivers/vpci/header.c
>> @@ -122,19 +122,6 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>>      bool map = cmd & PCI_COMMAND_MEMORY;
>>      unsigned int i;
>>  
>> -    /*
>> -     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
>> -     * can be trapped (and emulated) by Xen when the memory decoding bit is
>> -     * enabled.
>> -     *
>> -     * FIXME: punching holes after the p2m has been set up might be racy for
>> -     * DomU usage, needs to be revisited.
>> -     */
>> -#ifdef CONFIG_HAS_PCI_MSI
>> -    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
>> -        return;
>> -#endif
>> -
>>      for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
>>      {
>>          struct vpci_bar *bar = &header->bars[i];
>> @@ -164,6 +151,19 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>>              bar->enabled = map;
>>      }
>>  
>> +    /*
>> +     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
>> +     * can be trapped (and emulated) by Xen when the memory decoding bit is
>> +     * enabled.
>> +     *
>> +     * FIXME: punching holes after the p2m has been set up might be racy for
>> +     * DomU usage, needs to be revisited.
>> +     */
>> +#ifdef CONFIG_HAS_PCI_MSI
>> +    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
>> +        return;
>> +#endif
>> +
>>      if ( !rom_only )
>>      {
>>          pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
>> diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
>> index 516282205a53..142cfbae59d5 100644
>> --- a/xen/drivers/vpci/msix.c
>> +++ b/xen/drivers/vpci/msix.c
>> @@ -598,6 +598,10 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
>>      if ( !pdev->vpci->msix )
>>          return 0;
>>  
>> +    if ( !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_TABLE) &&
>> +         !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_PBA) )
>> +        return 0;
> 
> What if one is enabled and the other isn't? Doesn't the check need to move ...
> 
>>      /* Make sure there's a hole for the MSIX table/PBA in the p2m. */
>>      for ( i = 0; i < ARRAY_SIZE(pdev->vpci->msix->tables); i++ )
>>      {
> 
> ... into the loop,

Yes, will do.

> and then apparently also need mirroring in the hwdom-only
> loop further down?

I don't think that's necessary, the logic there is idempotent, and it's not
dealing with p2m.

Thanks for taking a look.

Re: [PATCH v2] vpci/msix: check for BARs enabled in vpci_make_msix_hole

[Stewart Hildebrand]

On 2/24/26 05:57, Roger Pau Monné wrote:
> On Mon, Feb 23, 2026 at 09:56:24PM -0500, Stewart Hildebrand wrote:
>> A hotplugged PCI device may be added uninitialized. In particular,
>> memory decoding might be disabled and the BARs might be zeroed. In this
>> case, the BARs will not be mapped in p2m. However, vpci_make_msix_hole()
>> unconditionally attempts to punch holes in p2m, leading to init_msix()
>> failing:
>>
>> (XEN) d0v0 0000:01:00.0: existing mapping (mfn: 1c1880 type: 0) at 0 clobbers MSIX MMIO area
>> (XEN) d0 0000:01:00.0: init legacy cap 17 fail rc=-17, mask it
>>
>> vpci_make_msix_hole() should only attempt to punch holes if the BARs
>> containing the MSI-X/PBA tables are mapped in p2m. Introduce a helper
>> for checking if a BAR is enabled, and add a check for the situation
>> inside vpci_make_msix_hole().
>>
>> Move the vpci_make_msix_hole() call within modify_decoding() to after
>> setting ->enabled.
> 
> I would maybe make it clear that the movement of the
> vpci_make_msix_hole() call in modify_decoding() is due to the extra
> requirement added in this patch that ->enabled must be set before
> calling the function.
> 
> "As a result of the newly introduced checks in vpci_make_msix_hole(),
> move the ..."
> 
> Or something along the lines.

Will do

>>
>> Fixes: ee2eb6849d50 ("vpci: Refactor REGISTER_VPCI_INIT")
>> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
>> ---
>> Pipeline: https://gitlab.com/xen-project/people/stewarthildebrand/xen/-/pipelines/2344925375
>>
>> v1->v2:
>> * new title, was ("vpci/msix: conditionally invoke vpci_make_msix_hole")
>> * move BAR enabled check to inside vpci_make_msix_hole()
>> * introduce vmsix_table_bar_valid() helper
>> * move vpci_make_msix_hole() call within modify_decoding() to after
>>   setting ->enabled
>> * split typo fixup to separate patch
>>
>> v1: https://lore.kernel.org/xen-devel/20250812151744.460953-1-stewart.hildebrand@amd.com/T/#t
>> ---
>>  xen/drivers/vpci/header.c | 26 +++++++++++++-------------
>>  xen/drivers/vpci/msix.c   |  4 ++++
>>  xen/include/xen/vpci.h    |  6 ++++++
>>  3 files changed, 23 insertions(+), 13 deletions(-)
>>
>> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
>> index 739a5f610e91..6a28e07a625b 100644
>> --- a/xen/drivers/vpci/header.c
>> +++ b/xen/drivers/vpci/header.c
>> @@ -122,19 +122,6 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>>      bool map = cmd & PCI_COMMAND_MEMORY;
>>      unsigned int i;
>>  
>> -    /*
>> -     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
>> -     * can be trapped (and emulated) by Xen when the memory decoding bit is
>> -     * enabled.
>> -     *
>> -     * FIXME: punching holes after the p2m has been set up might be racy for
>> -     * DomU usage, needs to be revisited.
>> -     */
>> -#ifdef CONFIG_HAS_PCI_MSI
>> -    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
>> -        return;
>> -#endif
>> -
>>      for ( i = 0; i < ARRAY_SIZE(header->bars); i++ )
>>      {
>>          struct vpci_bar *bar = &header->bars[i];
>> @@ -164,6 +151,19 @@ static void modify_decoding(const struct pci_dev *pdev, uint16_t cmd,
>>              bar->enabled = map;
>>      }
>>  
>> +    /*
>> +     * Make sure there are no mappings in the MSIX MMIO areas, so that accesses
>> +     * can be trapped (and emulated) by Xen when the memory decoding bit is
>> +     * enabled.
>> +     *
>> +     * FIXME: punching holes after the p2m has been set up might be racy for
>> +     * DomU usage, needs to be revisited.
>> +     */
>> +#ifdef CONFIG_HAS_PCI_MSI
>> +    if ( map && !rom_only && vpci_make_msix_hole(pdev) )
>> +        return;
>> +#endif
>> +
>>      if ( !rom_only )
>>      {
>>          pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
>> diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
>> index 516282205a53..142cfbae59d5 100644
>> --- a/xen/drivers/vpci/msix.c
>> +++ b/xen/drivers/vpci/msix.c
>> @@ -598,6 +598,10 @@ int vpci_make_msix_hole(const struct pci_dev *pdev)
>>      if ( !pdev->vpci->msix )
>>          return 0;
>>  
>> +    if ( !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_TABLE) &&
>> +         !vmsix_table_bar_valid(pdev->vpci, VPCI_MSIX_PBA) )
>> +        return 0;
> 
> As Jan pointed out, this needs to be moved inside the loop.

Will do.

Thanks!