Hi, On Tue, Nov 28, 2023 at 06:05:20PM +0100, David Hildenbrand wrote: > On 27.11.23 16:04, Alexandru Elisei wrote: > > Hi, > > > > On Fri, Nov 24, 2023 at 08:51:38PM +0100, David Hildenbrand wrote: > > > On 19.11.23 17:57, Alexandru Elisei wrote: > > > > Tag storage memory requires that the tag storage pages used for data are > > > > always migratable when they need to be repurposed to store tags. > > > > > > > > If ARCH_KEEP_MEMBLOCK is enabled, kexec will scan all non-reserved > > > > memblocks to find a suitable location for copying the kernel image. The > > > > kernel image, once loaded, cannot be moved to another location in physical > > > > memory. The initialization code for the tag storage reserves the memblocks > > > > for the tag storage pages, which means kexec will not use them, and the tag > > > > storage pages can be migrated at any time, which is the desired behaviour. > > > > > > > > However, if ARCH_KEEP_MEMBLOCK is not selected, kexec will not skip a > > > > region unless the memory resource has the IORESOURCE_SYSRAM_DRIVER_MANAGED > > > > flag, which isn't currently set by the tag storage initialization code. > > > > > > > > Make ARM64_MTE_TAG_STORAGE depend on ARCH_KEEP_MEMBLOCK to make it explicit > > > > that that the Kconfig option required for it to work correctly. > > > > > > > > Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx> > > > > --- > > > > arch/arm64/Kconfig | 1 + > > > > 1 file changed, 1 insertion(+) > > > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > > index 047487046e8f..efa5b7958169 100644 > > > > --- a/arch/arm64/Kconfig > > > > +++ b/arch/arm64/Kconfig > > > > @@ -2065,6 +2065,7 @@ config ARM64_MTE > > > > if ARM64_MTE > > > > config ARM64_MTE_TAG_STORAGE > > > > bool "Dynamic MTE tag storage management" > > > > + depends on ARCH_KEEP_MEMBLOCK > > > > select CONFIG_CMA > > > > help > > > > Adds support for dynamic management of the memory used by the hardware > > > > > > Doesn't arm64 select that unconditionally? Why is this required then? > > > > I've added this patch to make the dependancy explicit. If, in the future, arm64 > > stops selecting ARCH_KEEP_MEMBLOCK, I thinkg it would be very easy to miss the > > fact that tag storage depends on it. So this patch is not required per-se, it's > > there to document the dependancy. > > I see. Could you add some static_assert / BUILD_BUG_ON instead? I can do that, sure. Thanks, Alex > > I suspect there are plenty other (undocumented) reasons why > ARCH_KEEP_MEMBLOCK has to be enabled for now, and none sets > ARCH_KEEP_MEMBLOCK, I suspect/ > > -- > Cheers, > > David / dhildenb >
