On Fri, May 29, 2015 at 4:39 AM, Ross Zwisler <zwisler@xxxxxxxxx> wrote: > On Thu, 2015-05-28 at 15:47 -0700, Dan Williams wrote: >> On Thu, May 28, 2015 at 3:35 PM, Ross Zwisler >> <ross.zwisler@xxxxxxxxxxxxxxx> wrote: >> > Even though we use ioremap_nocache() to map our persistent memory >> > in the >> > pmem driver, the memory we are mapping behaves like normal memory >> > and >> > not I/O memory in that it can be accessed using regular memcpy() >> > operations and doesn't need to go through memcpy_toio() and >> > memcpy_fromio(). Force casting the pointers received from >> > ioremap_nocache() and given to iounmap() gives us the correct >> > behavior >> > and makes sparse happy. >> > >> > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> >> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> >> > Cc: linux-nvdimm@xxxxxxxxxxxx >> > --- >> > drivers/block/nd/pmem.c | 7 ++++--- >> > 1 file changed, 4 insertions(+), 3 deletions(-) >> > >> > diff --git a/drivers/block/nd/pmem.c b/drivers/block/nd/pmem.c >> > index 5e8c9c629f22..a8712e41e7f5 100644 >> > --- a/drivers/block/nd/pmem.c >> > +++ b/drivers/block/nd/pmem.c >> > @@ -163,7 +163,8 @@ static struct pmem_device *pmem_alloc(struct >> > device *dev, struct resource *res, >> > * of the CPU caches in case of a crash. >> > */ >> > err = -ENOMEM; >> > - pmem->virt_addr = ioremap_nocache(pmem->phys_addr, pmem >> > ->size); >> > + pmem->virt_addr = (__force void *)ioremap_nocache(pmem >> > ->phys_addr, >> > + pmem->size); >> >> I think I'd rather see casting when ->virt_addr is used (the >> __io_virt() helper can be used to make this a tad cleaner), or >> provide >> ioremap apis that don't attach __iomem to their return value. >> Because >> in this and other cases ioremap() is being on non "i/o" memory. > > The reason that I thought this was cleaner was that now when you look > at the pmem->virt_addr definition it is just a clean void* with no > annotations. This correctly describes the memory to the user (it's > usable as regular memory, it's in the kernel address space, etc.). > > Having the pointer itself annotated with __iomem feels weird to me > because a random well meaning user could incorrectly try to use it as > I/O memory. pmem->virt_addr does not leak outside the driver to random well meaning users. I think we have two options, provide physical address remap helpers from the outset (memremap()?) that don't attach __iomem, or put the casts on the non-iomem usages. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
