Re: [PATCH 1/4] bus/pci: Use force-noreplace flag when mapping PCI resources

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 5/6/2025 7:40 PM, Jake Freeland wrote:
> When mapping PCI resources in secondary processes, use the
> RTE_MAP_FORCE_ADDRESS_NOREPLACE flag to indicate that the
> mapping must be made at the provided address.
> 
> Without this flag, the kernel might return a different address for
> the mapping, even if the requested region was available.
> 
> Signed-off-by: Jake Freeland <jfree@FreeBSD.org>
> ---
>   drivers/bus/pci/pci_common_uio.c | 4 +++-
>   lib/eal/common/eal_private.h     | 7 ++++++-
>   lib/eal/include/rte_eal_paging.h | 7 ++++++-
>   lib/eal/unix/eal_unix_memory.c   | 8 +++++++-
>   4 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/pci/pci_common_uio.c b/drivers/bus/pci/pci_common_uio.c
> index 30503bd23a..71974e9f56 100644
> --- a/drivers/bus/pci/pci_common_uio.c
> +++ b/drivers/bus/pci/pci_common_uio.c
> @@ -10,6 +10,7 @@
>   #include <sys/mman.h>
>   
>   #include <rte_eal.h>
> +#include <rte_eal_paging.h>
>   #include <rte_pci.h>
>   #include <rte_bus_pci.h>
>   #include <rte_tailq.h>
> @@ -58,7 +59,8 @@ pci_uio_map_secondary(struct rte_pci_device *dev)
>   
>   			void *mapaddr = pci_map_resource(uio_res->maps[i].addr,
>   					fd, (off_t)uio_res->maps[i].offset,
> -					(size_t)uio_res->maps[i].size, 0);
> +					(size_t)uio_res->maps[i].size,
> +					RTE_MAP_FORCE_ADDRESS_NOREPLACE);
>   
>   			/* fd is not needed in secondary process, close it */
>   			close(fd);
> diff --git a/lib/eal/common/eal_private.h b/lib/eal/common/eal_private.h
> index 04ba8ddb86..aaeb140eaf 100644
> --- a/lib/eal/common/eal_private.h
> +++ b/lib/eal/common/eal_private.h
> @@ -211,7 +211,12 @@ enum eal_mem_reserve_flags {
>   	 * @see RTE_MAP_FORCE_ADDRESS for description of possible consequences
>   	 *      (although implementations are not required to use it).
>   	 */
> -	EAL_RESERVE_FORCE_ADDRESS = 1 << 1
> +	EAL_RESERVE_FORCE_ADDRESS = 1 << 1,
> +	/**
> +	 * Force reserving memory at the requested address, but fail if a
> +	 * preexisting mapping collides with the request.
> +	 */
> +	EAL_RESERVE_FORCE_ADDRESS_NOREPLACE = 1 << 2,
>   };
>   
>   /**
> diff --git a/lib/eal/include/rte_eal_paging.h b/lib/eal/include/rte_eal_paging.h
> index c60317d0f5..7b1983b615 100644
> --- a/lib/eal/include/rte_eal_paging.h
> +++ b/lib/eal/include/rte_eal_paging.h
> @@ -34,7 +34,12 @@ enum rte_map_flags {
>   	 * may remove all other mappings in the requested region. However,
>   	 * it is not required to do so, thus mapping with this flag may fail.
>   	 */
> -	RTE_MAP_FORCE_ADDRESS = 1 << 3
> +	RTE_MAP_FORCE_ADDRESS = 1 << 3,
> +	/**
> +	 * Force mapping to the requested address, but fail if a preexisting
> +	 * mapping collides with the request.
> +	 */
> +	RTE_MAP_FORCE_ADDRESS_NOREPLACE = 1 << 4,
>   };
>   
>   /**
> diff --git a/lib/eal/unix/eal_unix_memory.c b/lib/eal/unix/eal_unix_memory.c
> index c540f1e838..61e914b8db 100644
> --- a/lib/eal/unix/eal_unix_memory.c
> +++ b/lib/eal/unix/eal_unix_memory.c
> @@ -17,11 +17,13 @@
>   #ifdef RTE_EXEC_ENV_LINUX
>   #define EAL_DONTDUMP MADV_DONTDUMP
>   #define EAL_DODUMP   MADV_DODUMP
> +#define EAL_FIXED_NOREPLACE MAP_FIXED_NOREPLACE

Is this available in all supported Linux kernel versions?

-- 
Thanks,
Anatoly