[dpdk-dev] [PATCH] pci_vfio: Support 64KB kernel page_size with vfio-pci driver

Burakov, Anatoly anatoly.burakov at intel.com
Wed Oct 24 11:09:18 CEST 2018


On 24-Oct-18 3:20 AM, tone.zhang wrote:
> With a larger PAGE_SIZE it is possible for the MSI table to very
> close to the end of the BAR s.t. when we align the MSI table to
> the PAGE_SIZE, the end offset of the MSI table is out the PCI BAR
> boundary.
> 
> This patch addresses the issue by comparing both the start and the
> end offset of the MSI table with the BAR size.
> 
> The patch fixes the debug log as below:
> EAL: Skipping BAR0
> 
> Signed-off-by: tone.zhang <tone.zhang at arm.com>
> Reviewed-by: Gavin Hu <Gavin.Hu at arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
> Reviewed-by: Steve Capper <Steve.Capper at arm.com>
> ---
>   drivers/bus/pci/linux/pci_vfio.c | 25 +++++++++++++++++++++----
>   1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
> index b1f0683..1373345 100644
> --- a/drivers/bus/pci/linux/pci_vfio.c
> +++ b/drivers/bus/pci/linux/pci_vfio.c
> @@ -445,9 +445,11 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>   	struct pci_msix_table *msix_table = &vfio_res->msix_table;
>   	struct pci_map *bar = &vfio_res->maps[bar_index];
>   
> -	if (bar->size == 0)
> +	if (bar->size == 0) {
>   		/* Skip this BAR */
> +		RTE_LOG(INFO, EAL, "Skipping this BAR%d\n", bar_index);
>   		return 0;

I feel like "this" is unnecessary here - just "Skipping BAR%d" should be 
enough :)

> +	}
>   
>   	if (msix_table->bar_index == bar_index) {
>   		/*
> @@ -457,7 +459,12 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>   		uint32_t table_start = msix_table->offset;
>   		uint32_t table_end = table_start + msix_table->size;
>   		table_end = (table_end + ~PAGE_MASK) & PAGE_MASK;
> -		table_start &= PAGE_MASK;
> +		table_start = (table_start + ~PAGE_MASK) & PAGE_MASK;

IMO these two additions should be replaced by RTE_ALIGN by page size. 
Makes the purpose of the code much clearer.

> +		/* after rounding to PAGE_SIZE, it is over the bar->size,
> +		 * fall back to the MSI-X table offset in the bar.
> +		*/
> +		if (table_start >= bar->size)
> +			table_start = msix_table->offset;

If i understand things correctly, msix_table->offset value here may be 
unaligned, so falling back to this value may cause mapping failure, 
because we later use this value as a size of mapping (which needs to be 
page aligned). Shouldn't this be aligned using RTE_ALIGN_FLOOR by page size?

>   
>   		if (table_start == 0 && table_end >= bar->size) {
>   			/* Cannot map this BAR */
> @@ -469,8 +476,18 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct mapped_pci_resource *vfio_res,
>   
>   		memreg[0].offset = bar->offset;
>   		memreg[0].size = table_start;
> -		memreg[1].offset = bar->offset + table_end;
> -		memreg[1].size = bar->size - table_end;
> +		if (bar->size < table_end) {
> +			/*
> +			 * after rounding to PAGE_SIZE we don't have any space
> +			 * left after the MSI table, so don't try and map it.
> +			*/
> +			memreg[1].offset = 0;
> +			memreg[1].size = 0;
> +		}
> +		else {
> +			memreg[1].offset = bar->offset + table_end;
> +			memreg[1].size = bar->size - table_end;
> +		}
>   
>   		RTE_LOG(DEBUG, EAL,
>   			"Trying to map BAR%d that contains the MSI-X "
> 


-- 
Thanks,
Anatoly


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