diff mbox series

[v2,2/5] PCI: dwc: Check alloc_page() return value

Message ID 20200924190623.3251c2ac@xhacker.debian
State New
Headers show
Series PCI: dwc: improve msi handling | expand

Commit Message

Jisheng Zhang Sept. 24, 2020, 11:06 a.m. UTC 
We need to check alloc_page() succeed or not before continuing.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Marc Zyngier Sept. 29, 2020, 5:29 p.m. UTC | #1 
On 2020-09-24 12:06, Jisheng Zhang wrote:
> We need to check alloc_page() succeed or not before continuing.
> 
> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 0a19de946351..9e04e8ef3aa4 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -303,6 +303,11 @@ void dw_pcie_msi_init(struct pcie_port *pp)
>  	u64 msi_target;
> 
>  	pp->msi_page = alloc_page(GFP_KERNEL);
> +	if (!pp->msi_page) {
> +		dev_err(dev, "Failed to alloc MSI page\n");

A failing allocation will already scream, so there is no need to
add insult to injury.

More importantly, what is this MSI page ever used for? If I remember
well, this is just a random address that never gets written to.

So why do we allocate a page here? Why do we bother with this DMA
mapping?

         M.
Jisheng Zhang Sept. 30, 2020, 1:23 a.m. UTC | #2 
Hi Marc,

On Tue, 29 Sep 2020 18:29:52 +0100 Marc Zyngier wrote:

> 
> 
> On 2020-09-24 12:06, Jisheng Zhang wrote:
> > We need to check alloc_page() succeed or not before continuing.
> >
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> > b/drivers/pci/controller/dwc/pcie-designware-host.c
> > index 0a19de946351..9e04e8ef3aa4 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > @@ -303,6 +303,11 @@ void dw_pcie_msi_init(struct pcie_port *pp)
> >       u64 msi_target;
> >
> >       pp->msi_page = alloc_page(GFP_KERNEL);
> > +     if (!pp->msi_page) {
> > +             dev_err(dev, "Failed to alloc MSI page\n");  
> 
> A failing allocation will already scream, so there is no need to
> add insult to injury.
> 
> More importantly, what is this MSI page ever used for? If I remember
> well, this is just a random address that never gets written to.
> 
> So why do we allocate a page here? Why do we bother with this DMA
> mapping?
> 

Ard and Rob also pointed out that there's no need to allocate a page, instead,
we could use an address in the driver data for MSI address. So I refactored
the patches and verified this solution works fine. Could you please review
the V5?


Thanks
diff mbox series

Patch

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 0a19de946351..9e04e8ef3aa4 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -303,6 +303,11 @@  void dw_pcie_msi_init(struct pcie_port *pp)
 	u64 msi_target;
 
 	pp->msi_page = alloc_page(GFP_KERNEL);
+	if (!pp->msi_page) {
+		dev_err(dev, "Failed to alloc MSI page\n");
+		return;
+	}
+
 	pp->msi_data = dma_map_page(dev, pp->msi_page, 0, PAGE_SIZE,
 				    DMA_FROM_DEVICE);
 	if (dma_mapping_error(dev, pp->msi_data)) {