On Tue, 2015-12-15 at 09:21 -0800, Dan Williams wrote: > On Tue, Dec 15, 2015 at 8:59 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote: > > ACPI 6.0 defines NFIT table and new persistent memory types for > > EFI memory table (EFI_PERSISTENT_MEMORY) and e820 table (E820_PMEM). > > > > setup_e820() enabled by EFI_STUB converts EFI_PERSISTENT_MEMORY to > > E820_PMEM for the e820_map table on x86 EFI platforms. When EFI_STUB > > is disabled, x86 kernels rely on the bootloader to perform this > > conversion. > > > > It was found that the upstream grub bootloader since 2012 has a bug > > that converts EFI_PERSISTENT_MEMORY (or any new type) to E820_RAM, > > which causes the kernel to use persistent memory ranges as regular > > memory and corrupts the data in NVDIMM. > > > > Therefore, this patch sets ACPI_NFIT to depend on EFI_STUB on x86. > > This assures that ACPI_NFIT kernels are self-contained and are > > protected from the upstream grub bug on x86. > > > > Note, X86_PMEM_LEGACY allows the kernel to use the pmem driver on > > pre-ACPI 6.0 platforms, and does not require ACPI_NFIT enabled. > > > > References: > > http://www.mail-archive.com/grub-devel@xxxxxxx/msg23961.html > > Reported-by: Robert Elliott <elliott@xxxxxxx> > > Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx> > > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> > > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > > --- > > drivers/acpi/Kconfig | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig > > index 5eef4cb..5368baa 100644 > > --- a/drivers/acpi/Kconfig > > +++ b/drivers/acpi/Kconfig > > @@ -441,6 +441,7 @@ config ACPI_NFIT > > depends on PHYS_ADDR_T_64BIT > > depends on BLK_DEV > > depends on ARCH_HAS_MMIO_FLUSH > > + depends on !X86 || (X86 && EFI_STUB) > > select LIBNVDIMM > > help > > Infrastructure to probe ACPI 6 compliant platforms for > > This seems wrong to me. > > In general Kconfig "depends on" are only about compile-time code > dependency, not about working around random bugs in external projects. I agree that they do not have a compile dependency, and it looks rather odd. On the other hand, proper support of the ACPI NFIT extensions has a functional dependency to setup_e820() as this is the only code that can handle the EFI_PERSISTENT_MEMORY type today. Thanks, -Toshi -- 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
