Add a new function to emulate extended capability list for dom0,
and call it in init_header(). So that it will be easy to hide a
extended capability whose initialization fails.

As for the extended capability list of domU, just move the logic
into above function and keep hiding it for domU.

Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
---
cc: "Roger Pau Monné" <roger.pau@citrix.com>
---
v4->v5 changes:
* Add check: if capability list of hardware has a overlap, print warning and return 0.

v3->v4 changes:
* Add check "if ( !header )   return 0;" to avoid adding handler for
  device that has no extended capabilities.

v2->v3 changes:
* In vpci_init_ext_capability_list(), when domain is domU, directly return after adding a handler(hiding all extended capability for domU).
* In vpci_init_ext_capability_list(), change condition to be "while ( pos >= 0x100U && ttl-- )" instead of "while ( pos && ttl-- )".
* Add new function vpci_hw_write32, and pass it to extended capability handler for dom0.

v1->v2 changes:
new patch

Best regards,
Jiqian Chen.
---
 xen/drivers/vpci/header.c | 47 ++++++++++++++++++++++++++++++++-------
 xen/drivers/vpci/vpci.c   |  6 +++++
 xen/include/xen/vpci.h    |  2 ++
 3 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index d26cbba08ee1..4b2f761c9c24 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -836,6 +836,42 @@ static int vpci_init_capability_list(struct pci_dev *pdev)
                                   PCI_STATUS_RSVDZ_MASK);
 }
 
+static int vpci_init_ext_capability_list(struct pci_dev *pdev)
+{
+    unsigned int pos = PCI_CFG_SPACE_SIZE, ttl = 480;
+
+    if ( !is_hardware_domain(pdev->domain) )
+        /* Extended capabilities read as zero, write ignore for guest */
+        return vpci_add_register(pdev->vpci, vpci_read_val, NULL,
+                                 pos, 4, (void *)0);
+
+    while ( pos >= PCI_CFG_SPACE_SIZE && ttl-- )
+    {
+        uint32_t header = pci_conf_read32(pdev->sbdf, pos);
+        int rc;
+
+        if ( !header )
+            return 0;
+
+        rc = vpci_add_register(pdev->vpci, vpci_read_val, vpci_hw_write32,
+                               pos, 4, (void *)(uintptr_t)header);
+        if ( rc == -EEXIST )
+        {
+            printk(XENLOG_WARNING
+                   "%pd %pp: overlap in extended cap list, offset %#x\n",
+                   pdev->domain, &pdev->sbdf, pos);
+            return 0;
+        }
+
+        if ( rc )
+            return rc;
+
+        pos = PCI_EXT_CAP_NEXT(header);
+    }
+
+    return 0;
+}
+
 static int cf_check init_header(struct pci_dev *pdev)
 {
     uint16_t cmd;
@@ -888,14 +924,9 @@ static int cf_check init_header(struct pci_dev *pdev)
     if ( rc )
         return rc;
 
-    if ( !is_hwdom )
-    {
-        /* Extended capabilities read as zero, write ignore */
-        rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL, 0x100, 4,
-                               (void *)0);
-        if ( rc )
-            return rc;
-    }
+    rc = vpci_init_ext_capability_list(pdev);
+    if ( rc )
+        return rc;
 
     if ( pdev->ignore_bars )
         return 0;
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 09988f04c27c..8474c0e3b995 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -267,6 +267,12 @@ void cf_check vpci_hw_write16(
     pci_conf_write16(pdev->sbdf, reg, val);
 }
 
+void cf_check vpci_hw_write32(
+    const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data)
+{
+    pci_conf_write32(pdev->sbdf, reg, val);
+}
+
 int vpci_add_register_mask(struct vpci *vpci, vpci_read_t *read_handler,
                            vpci_write_t *write_handler, unsigned int offset,
                            unsigned int size, void *data, uint32_t ro_mask,
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index fc8d5b470b0b..61d16cc8b897 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -80,6 +80,8 @@ void cf_check vpci_hw_write8(
     const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data);
 void cf_check vpci_hw_write16(
     const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data);
+void cf_check vpci_hw_write32(
+    const struct pci_dev *pdev, unsigned int reg, uint32_t val, void *data);
 
 /*
  * Check for pending vPCI operations on this vcpu. Returns true if the vcpu
-- 
2.34.1

On Mon, May 26, 2025 at 05:45:52PM +0800, Jiqian Chen wrote:
> Add a new function to emulate extended capability list for dom0,
> and call it in init_header(). So that it will be easy to hide a
> extended capability whose initialization fails.
> 
> As for the extended capability list of domU, just move the logic
> into above function and keep hiding it for domU.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> ---
> cc: "Roger Pau Monné" <roger.pau@citrix.com>
> ---
> v4->v5 changes:
> * Add check: if capability list of hardware has a overlap, print warning and return 0.
> 
> v3->v4 changes:
> * Add check "if ( !header )   return 0;" to avoid adding handler for
>   device that has no extended capabilities.
> 
> v2->v3 changes:
> * In vpci_init_ext_capability_list(), when domain is domU, directly return after adding a handler(hiding all extended capability for domU).
> * In vpci_init_ext_capability_list(), change condition to be "while ( pos >= 0x100U && ttl-- )" instead of "while ( pos && ttl-- )".
> * Add new function vpci_hw_write32, and pass it to extended capability handler for dom0.
> 
> v1->v2 changes:
> new patch
> 
> Best regards,
> Jiqian Chen.
> ---
>  xen/drivers/vpci/header.c | 47 ++++++++++++++++++++++++++++++++-------
>  xen/drivers/vpci/vpci.c   |  6 +++++
>  xen/include/xen/vpci.h    |  2 ++
>  3 files changed, 47 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index d26cbba08ee1..4b2f761c9c24 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -836,6 +836,42 @@ static int vpci_init_capability_list(struct pci_dev *pdev)
>                                    PCI_STATUS_RSVDZ_MASK);
>  }
>  
> +static int vpci_init_ext_capability_list(struct pci_dev *pdev)
> +{
> +    unsigned int pos = PCI_CFG_SPACE_SIZE, ttl = 480;

I think you can drop the ttl variable, as said by Jan in a previous
review, the purpose of that counter is to detect overlaps in the PCIe
config space, but for the context here the call to vpci_add_register()
already serves that purpose by returning -EEXIST.

Thanks, Roger.

On 2025/6/5 19:24, Roger Pau Monné wrote:
> On Mon, May 26, 2025 at 05:45:52PM +0800, Jiqian Chen wrote:
>> Add a new function to emulate extended capability list for dom0,
>> and call it in init_header(). So that it will be easy to hide a
>> extended capability whose initialization fails.
>>
>> As for the extended capability list of domU, just move the logic
>> into above function and keep hiding it for domU.
>>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>> ---
>> cc: "Roger Pau Monné" <roger.pau@citrix.com>
>> ---
>> v4->v5 changes:
>> * Add check: if capability list of hardware has a overlap, print warning and return 0.
>>
>> v3->v4 changes:
>> * Add check "if ( !header )   return 0;" to avoid adding handler for
>>   device that has no extended capabilities.
>>
>> v2->v3 changes:
>> * In vpci_init_ext_capability_list(), when domain is domU, directly return after adding a handler(hiding all extended capability for domU).
>> * In vpci_init_ext_capability_list(), change condition to be "while ( pos >= 0x100U && ttl-- )" instead of "while ( pos && ttl-- )".
>> * Add new function vpci_hw_write32, and pass it to extended capability handler for dom0.
>>
>> v1->v2 changes:
>> new patch
>>
>> Best regards,
>> Jiqian Chen.
>> ---
>>  xen/drivers/vpci/header.c | 47 ++++++++++++++++++++++++++++++++-------
>>  xen/drivers/vpci/vpci.c   |  6 +++++
>>  xen/include/xen/vpci.h    |  2 ++
>>  3 files changed, 47 insertions(+), 8 deletions(-)
>>
>> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
>> index d26cbba08ee1..4b2f761c9c24 100644
>> --- a/xen/drivers/vpci/header.c
>> +++ b/xen/drivers/vpci/header.c
>> @@ -836,6 +836,42 @@ static int vpci_init_capability_list(struct pci_dev *pdev)
>>                                    PCI_STATUS_RSVDZ_MASK);
>>  }
>>  
>> +static int vpci_init_ext_capability_list(struct pci_dev *pdev)
>> +{
>> +    unsigned int pos = PCI_CFG_SPACE_SIZE, ttl = 480;
> 
> I think you can drop the ttl variable, as said by Jan in a previous
> review, the purpose of that counter is to detect overlaps in the PCIe
> config space, but for the context here the call to vpci_add_register()
> already serves that purpose by returning -EEXIST.
Will do in next version.

> 
> Thanks, Roger.

-- 
Best regards,
Jiqian Chen.