On Tue, Nov 24, 2015 at 5:28 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > On Tue, Nov 24, 2015 at 4:47 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >> On Tue, 24 Nov 2015 16:34:19 -0800 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> >>> > IOW, a very good description of the problem-being-solved would help out >>> > a lot here... >>> >>> I'll fold the eventual result of this discussion into the changelog if >>> I can convince you it's worth moving forward. >> >> I'm easily convinced ;) Please let's get all the info into the right >> place, make sure it answers the thus-far-asked questions (at least) and >> we'll take it from there. >> >> And please do have a think about switching as much as possible over to >> runtime-configurability. Because "please echo foo > /proc" is a heck >> of a lot nicer than "please reboot with iomem=" which is a heck of a lot >> nicer than "please ask vendor for a new kernel". > > Actually, we already have runtime configuration. For example, if you > want to muck with pmem via /dev/mem, just do this first: > > echo namespace0.0 > /sys/bus/nd/drivers/nd_pmem/unbind Here's the summary of the thread that I will add to the changelog: --- In general if a device driver is busily using a memory region it already informs other parts of the kernel to not touch it via request_mem_region(). /dev/mem should honor the same safety restriction by default. Debugging a device driver from userspace becomes more difficult with this enabled. Any application using /dev/mem or mmap of sysfs pci resources will now need to perform the extra step of either: 1/ Disabling the driver, for example: echo <device id> > /dev/bus/<parent bus>/drivers/<driver name>/unbind 2/ Rebooting with "iomem=relaxed" on the command line 3/ Recompiling with CONFIG_IO_STRICT_DEVMEM=n Traditional users of /dev/mem like dosemu are unaffected because the first 1MB of memory is not subject to the IO_STRICT_DEVMEM restriction. Legacy X configurations use /dev/mem to talk to graphics hardware, but that functionality has since moved to kernel graphics drivers. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
