Re: [dpdk-dev] [PATCH 1/8] eal: expose rte_eal_using_phys_addrs

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Fri, 30 Jun 2017 21:05:47 +0200, Jan Blunck <jblunck@infradead.org> wrote:
> On Thu, Jun 1, 2017 at 12:14 PM, Gaetan Rivet <gaetan.rivet@6wind.com> wrote:
> > This function was previously private to the EAL layer.
> > Other subsystems requires it, such as the PCI bus.
> >
> > This function is only exposed for linuxapps.
> >
> > In order not to force other components to include stdbool, which is
> > incompatible with several NIC drivers, the return type has
> > been changed from bool to int.
> >
> > Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> > ---
> >  lib/librte_eal/common/eal_private.h             | 11 -----
> >  lib/librte_eal/linuxapp/eal/Makefile            |  2 +
> >  lib/librte_eal/linuxapp/eal/eal_memory.c        |  3 +-
> >  lib/librte_eal/linuxapp/eal/eal_pci.c           |  1 +
> >  lib/librte_eal/linuxapp/eal/rte_eal_version.map |  1 +
> >  lib/librte_eal/linuxapp/eal/rte_memory_linux.h  | 64 +++++++++++++++++++++++++
> >  6 files changed, 70 insertions(+), 12 deletions(-)
> >  create mode 100644 lib/librte_eal/linuxapp/eal/rte_memory_linux.h
> >
> > diff --git a/lib/librte_eal/common/eal_private.h b/lib/librte_eal/common/eal_private.h
> > index 6d2206a..b7e4cc6 100644
> > --- a/lib/librte_eal/common/eal_private.h
> > +++ b/lib/librte_eal/common/eal_private.h
> > @@ -327,17 +327,6 @@ int rte_eal_hugepage_init(void);
> >   */
> >  int rte_eal_hugepage_attach(void);
> >
> > -/**
> > - * Returns true if the system is able to obtain
> > - * physical addresses. Return false if using DMA
> > - * addresses through an IOMMU.
> > - *
> > - * Drivers based on uio will not load unless physical
> > - * addresses are obtainable. It is only possible to get
> > - * physical addresses when running as a privileged user.
> > - */
> > -bool rte_eal_using_phys_addrs(void);
> > -
> >  /*
> >   * Validate a bus name.
> >   *
> > diff --git a/lib/librte_eal/linuxapp/eal/Makefile b/lib/librte_eal/linuxapp/eal/Makefile
> > index 640afd0..530e286 100644
> > --- a/lib/librte_eal/linuxapp/eal/Makefile
> > +++ b/lib/librte_eal/linuxapp/eal/Makefile
> > @@ -131,4 +131,6 @@ INC := rte_interrupts.h rte_kni_common.h rte_dom0_common.h
> >  SYMLINK-$(CONFIG_RTE_EXEC_ENV_LINUXAPP)-include/exec-env := \
> >         $(addprefix include/exec-env/,$(INC))
> >
> > +SYMLINK-$(CONFIG_RTE_EXEC_ENV_LINUXAPP)-include += rte_memory_linux.h
> > +
> >  include $(RTE_SDK)/mk/rte.lib.mk
> > diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
> > index ebe0683..072bfe4 100644
> > --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> > +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> > @@ -99,6 +99,7 @@
> >  #include "eal_internal_cfg.h"
> >  #include "eal_filesystem.h"
> >  #include "eal_hugepages.h"
> > +#include "rte_memory_linux.h"
> >
> >  #define PFN_MASK_SIZE  8
> >
> > @@ -1472,7 +1473,7 @@ rte_eal_hugepage_attach(void)
> >         return -1;
> >  }
> >
> > -bool
> > +int
> >  rte_eal_using_phys_addrs(void)
> >  {
> >         return phys_addrs_available;
> > diff --git a/lib/librte_eal/linuxapp/eal/eal_pci.c b/lib/librte_eal/linuxapp/eal/eal_pci.c
> > index 595622b..9d5b051 100644
> > --- a/lib/librte_eal/linuxapp/eal/eal_pci.c
> > +++ b/lib/librte_eal/linuxapp/eal/eal_pci.c
> > @@ -45,6 +45,7 @@
> >  #include "eal_filesystem.h"
> >  #include "eal_private.h"
> >  #include "eal_pci_init.h"
> > +#include "rte_memory_linux.h"
> >
> >  /**
> >   * @file
> > diff --git a/lib/librte_eal/linuxapp/eal/rte_eal_version.map b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> > index a5127d6..8916520 100644
> > --- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> > +++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> > @@ -207,5 +207,6 @@ DPDK_17.08 {
> >
> >         rte_bus_from_name;
> >         rte_bus_from_dev;
> > +       rte_eal_using_phys_addrs;  
> 
> Is this only for the UIO mapping? Would it be better to let UIO skip
> (and warn?) over RTE_BAD_PHYS_ADDR mappings? That way we don't need
> this export and its probably more resilient to bad mappings.
> 
> Thoughts? Olivier?

From what I see, rte_eal_using_phys_addrs() is used by:

	rte_eal_pci_map_device(struct rte_pci_device *dev)
	{
		...
	        case RTE_KDRV_IGB_UIO:
	        case RTE_KDRV_UIO_GENERIC:
		if (rte_eal_using_phys_addrs()) {
			/* map resources for devices that use uio */
			ret = pci_uio_map_resource(dev);
		}


Looking at pci_uio_map_resource() and its callees, I'm not sure it's
easy to replace it something else. The functions that would return
RTE_BAD_PHYS_ADDR (virt2phy-like) are not called there.