Re: [PATCH 3/4] x86/ioapic: Fix lost ioapic resource after hot-removal and hotadd

[Bjorn Helgaas]

On Wed, Jul 27, 2016 at 12:13:16AM +0800, Rui Wang wrote:
> ioapic resource at 0xfecxxxxx gets lost from /proc/iomem after
> hot-removing and then hot-adding the ioapic devices.
> 
> After system boot, in /proc/iomem:
> fec00000-fecfffff : PNP0003:00
>   fec00000-fec003ff : IOAPIC 0
>   fec01000-fec013ff : IOAPIC 1
>   fec40000-fec403ff : IOAPIC 2
>   fec80000-fec803ff : IOAPIC 3
>   fecc0000-fecc03ff : IOAPIC 4
> 
> Then hot-remove IOAPIC 2 and hot-add it again:
> fec00000-fecfffff : PNP0003:00
>   fec00000-fec003ff : IOAPIC 0
>   fec01000-fec013ff : IOAPIC 1
>   fec80000-fec803ff : IOAPIC 3
>   fecc0000-fecc03ff : IOAPIC 4
> 
> The range at 0xfec40000 is lost from /proc/iomem. It is because
> handle_ioapic_add() requests resource from either PCI config BAR or
> acpi _CRS, not both. But Intel platforms map the IOxAPIC registers

s/acpi/ACPI/
s/ioapic/IOAPIC/ throughout

> at both the PCI config BAR (called MBAR) and the 0xfecX_YZ00 to
> 0xfecX_Y2FF range (called ABAR). Both of the ranges should be claimed

I guess you mean the 0xfecX_YZ00-0xfecX_Y2FF range appears in _CRS?

> from /proc/iomem for exclusive use.
> 
> Signed-off-by: Rui Wang <rui.y.wang@xxxxxxxxx>
> ---
>  drivers/acpi/ioapic.c | 36 ++++++++++++++++++++----------------
>  1 file changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/acpi/ioapic.c b/drivers/acpi/ioapic.c
> index daf4a40..80b0b1a 100644
> --- a/drivers/acpi/ioapic.c
> +++ b/drivers/acpi/ioapic.c
> @@ -97,7 +97,7 @@ static acpi_status handle_ioapic_add(acpi_handle handle, u32 lvl,
>  	unsigned long long gsi_base;
>  	struct acpi_pci_ioapic *ioapic;
>  	struct pci_dev *dev = NULL;
> -	struct resource *res = NULL;
> +	struct resource *res = NULL, *pci_res, *crs_res;
>  	char *type = NULL;
>  
>  	if (!acpi_is_ioapic(handle, &type))
> @@ -137,23 +137,28 @@ static acpi_status handle_ioapic_add(acpi_handle handle, u32 lvl,
>  		pci_set_master(dev);
>  		if (pci_request_region(dev, 0, type))
>  			goto exit_disable;
> -		res = &dev->resource[0];
> +		pci_res = &dev->resource[0];
>  		ioapic->pdev = dev;
>  	} else {
>  		pci_dev_put(dev);
>  		dev = NULL;
> +	}
>  
> -		res = &ioapic->res;
> -		acpi_walk_resources(handle, METHOD_NAME__CRS, setup_res, res);
> -		if (res->flags == 0) {
> -			acpi_handle_warn(handle, "failed to get resource\n");
> -			goto exit_free;
> -		} else if (request_resource(&iomem_resource, res)) {
> -			acpi_handle_warn(handle, "failed to insert resource\n");
> -			goto exit_free;
> -		}
> +	crs_res = &ioapic->res;
> +	acpi_walk_resources(handle, METHOD_NAME__CRS, setup_res, crs_res);
> +	if (crs_res->flags == 0) {
> +		acpi_handle_warn(handle, "failed to get resource\n");
> +		goto exit_release;
> +	} else if (request_resource(&iomem_resource, crs_res)) {
> +		acpi_handle_warn(handle, "failed to insert resource\n");
> +		goto exit_release;
>  	}
>  
> +	/* try pci resource first, then "_CRS" resource */
> +	res = pci_res;
> +	if (!res || !res->flags)
> +		res = crs_res;
> +
>  	if (acpi_register_ioapic(handle, res->start, (u32)gsi_base)) {
>  		acpi_handle_warn(handle, "failed to register IOAPIC\n");
>  		goto exit_release;
> @@ -174,14 +179,13 @@ done:
>  exit_release:
>  	if (dev)
>  		pci_release_region(dev, 0);
> -	else
> -		release_resource(res);
> +	if (ioapic->res.flags && ioapic->res.parent)
> +		release_resource(&ioapic->res);
>  exit_disable:
>  	if (dev)
>  		pci_disable_device(dev);
>  exit_put:
>  	pci_dev_put(dev);
> -exit_free:
>  	kfree(ioapic);
>  exit:
>  	mutex_unlock(&ioapic_list_lock);
> @@ -218,9 +222,9 @@ int acpi_ioapic_remove(struct acpi_pci_root *root)
>  			pci_release_region(ioapic->pdev, 0);
>  			pci_disable_device(ioapic->pdev);
>  			pci_dev_put(ioapic->pdev);
> -		} else if (ioapic->res.flags && ioapic->res.parent) {
> -			release_resource(&ioapic->res);
>  		}
> +		if (ioapic->res.flags && ioapic->res.parent)
> +			release_resource(&ioapic->res);
>  		list_del(&ioapic->list);
>  		kfree(ioapic);
>  	}
> -- 
> 1.8.3.1
>