[PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[Wei Liu]

The intent of the code snippet is to always return 0 for both
PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.

The check misses PCI_INTERRUPT_PIN. This patch fixes that.

This is discovered by this call in VFIO:

    pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);

The old code does not set *val to 0 because it misses the check for
PCI_INTERRUPT_PIN. Garbage is returned in that case.

Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Cc: stable@kernel.org
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
---
v3:
* Change commit subject line and message per Bjorn's suggestion
v2:
* Change the commit subject line and message
* Change the code according to feedback
---
 drivers/pci/controller/pci-hyperv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 5992280e8110..cdd5be16021d 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1130,8 +1130,8 @@ static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
 		   PCI_CAPABILITY_LIST) {
 		/* ROM BARs are unimplemented */
 		*val = 0;
-	} else if (where >= PCI_INTERRUPT_LINE && where + size <=
-		   PCI_INTERRUPT_PIN) {
+	} else if ((where >= PCI_INTERRUPT_LINE && where + size <= PCI_INTERRUPT_PIN) ||
+		   (where >= PCI_INTERRUPT_PIN && where + size <= PCI_MIN_GNT)) {
 		/*
 		 * Interrupt Line and Interrupt PIN are hard-wired to zero
 		 * because this front-end only supports message-signaled
-- 
2.43.0

Re: [PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[Wei Liu]

On Mon, Jul 01, 2024 at 08:26:05PM +0000, Wei Liu wrote:
> The intent of the code snippet is to always return 0 for both
> PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.
> 
> The check misses PCI_INTERRUPT_PIN. This patch fixes that.
> 
> This is discovered by this call in VFIO:
> 
>     pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
> 
> The old code does not set *val to 0 because it misses the check for
> PCI_INTERRUPT_PIN. Garbage is returned in that case.
> 
> Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
> Cc: stable@kernel.org
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> Reviewed-by: Michael Kelley <mhklinux@outlook.com>

Bjorn & other PCI maintainers, do you want to pick this up via your
tree?

I can pick this up via the hyperv tree if you prefer.

Thanks,
Wei.

> ---
> v3:
> * Change commit subject line and message per Bjorn's suggestion
> v2:
> * Change the commit subject line and message
> * Change the code according to feedback
> ---
>  drivers/pci/controller/pci-hyperv.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 5992280e8110..cdd5be16021d 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -1130,8 +1130,8 @@ static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
>  		   PCI_CAPABILITY_LIST) {
>  		/* ROM BARs are unimplemented */
>  		*val = 0;
> -	} else if (where >= PCI_INTERRUPT_LINE && where + size <=
> -		   PCI_INTERRUPT_PIN) {
> +	} else if ((where >= PCI_INTERRUPT_LINE && where + size <= PCI_INTERRUPT_PIN) ||
> +		   (where >= PCI_INTERRUPT_PIN && where + size <= PCI_MIN_GNT)) {
>  		/*
>  		 * Interrupt Line and Interrupt PIN are hard-wired to zero
>  		 * because this front-end only supports message-signaled
> -- 
> 2.43.0
> 

Re: [PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[Krzysztof Wilczyński]

Hello,

> > The intent of the code snippet is to always return 0 for both
> > PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.
> > 
> > The check misses PCI_INTERRUPT_PIN. This patch fixes that.
> > 
> > This is discovered by this call in VFIO:
> > 
> >     pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
> > 
> > The old code does not set *val to 0 because it misses the check for
> > PCI_INTERRUPT_PIN. Garbage is returned in that case.
[...]
> 
> Bjorn & other PCI maintainers, do you want to pick this up via your
> tree?
> 
> I can pick this up via the hyperv tree if you prefer.

We will pick this up.  No worries.

	Krzysztof

Re: [PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[Wei Liu]

On Wed, Jul 03, 2024 at 05:12:47PM +0900, Krzysztof Wilczyński wrote:
> Hello,
> 
> > > The intent of the code snippet is to always return 0 for both
> > > PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.
> > > 
> > > The check misses PCI_INTERRUPT_PIN. This patch fixes that.
> > > 
> > > This is discovered by this call in VFIO:
> > > 
> > >     pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
> > > 
> > > The old code does not set *val to 0 because it misses the check for
> > > PCI_INTERRUPT_PIN. Garbage is returned in that case.
> [...]
> > 
> > Bjorn & other PCI maintainers, do you want to pick this up via your
> > tree?
> > 
> > I can pick this up via the hyperv tree if you prefer.
> 
> We will pick this up.  No worries.

Thank you very much!

> 
> 	Krzysztof
> 

Re: [PATCH v3] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

[Krzysztof Wilczyński]

Hello,

> The intent of the code snippet is to always return 0 for both
> PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.
> 
> The check misses PCI_INTERRUPT_PIN. This patch fixes that.
> 
> This is discovered by this call in VFIO:
> 
>     pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
> 
> The old code does not set *val to 0 because it misses the check for
> PCI_INTERRUPT_PIN. Garbage is returned in that case.

Applied to controller/hyperv, thank you!

[1/1] PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN
      https://git.kernel.org/pci/pci/c/fea93a3e5d5e

	Krzysztof