Re: [RESEND PATCH v1 1/1] PCI: microchip: Fix potential race in interrupt handling

[<Conor.Dooley@microchip.com>]

Hey all,
Is there anything you need from us on this patch?
Thanks,
Conor

On 05/04/2022 12:17, daire.mcnamara@microchip.com wrote:
> From: Daire McNamara <daire.mcnamara@microchip.com>
> 
> Clear MSI bit in ISTATUS register after reading it before
> handling individual MSI bits
> 
> This fixes a potential race condition pointed out by Bjorn Helgaas:
> https://lore.kernel.org/linux-pci/20220127202000.GA126335@bhelgaas/
> 
> Fixes: 6f15a9c9f941 ("PCI: microchip: Add Microchip PolarFire PCIe controller driver")
> Signed-off-by: Daire McNamara <daire.mcnamara@microchip.com>
> ---
> Adding linux-pci mailing list
>   drivers/pci/controller/pcie-microchip-host.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-microchip-host.c b/drivers/pci/controller/pcie-microchip-host.c
> index 29d8e81e4181..da8e3fdc97b3 100644
> --- a/drivers/pci/controller/pcie-microchip-host.c
> +++ b/drivers/pci/controller/pcie-microchip-host.c
> @@ -416,6 +416,7 @@ static void mc_handle_msi(struct irq_desc *desc)
>   
>   	status = readl_relaxed(bridge_base_addr + ISTATUS_LOCAL);
>   	if (status & PM_MSI_INT_MSI_MASK) {
> +		writel_relaxed(status & PM_MSI_INT_MSI_MASK, bridge_base_addr + ISTATUS_LOCAL);
>   		status = readl_relaxed(bridge_base_addr + ISTATUS_MSI);
>   		for_each_set_bit(bit, &status, msi->num_vectors) {
>   			ret = generic_handle_domain_irq(msi->dev_domain, bit);
> @@ -432,13 +433,8 @@ static void mc_msi_bottom_irq_ack(struct irq_data *data)
>   	void __iomem *bridge_base_addr =
>   		port->axi_base_addr + MC_PCIE_BRIDGE_ADDR;
>   	u32 bitpos = data->hwirq;
> -	unsigned long status;
>   
>   	writel_relaxed(BIT(bitpos), bridge_base_addr + ISTATUS_MSI);
> -	status = readl_relaxed(bridge_base_addr + ISTATUS_MSI);
> -	if (!status)
> -		writel_relaxed(BIT(PM_MSI_INT_MSI_SHIFT),
> -			       bridge_base_addr + ISTATUS_LOCAL);
>   }
>   
>   static void mc_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)