* Tony Lindgren <tony@xxxxxxxxxxx> [150429 07:42]: > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [150428 11:14]: > > On Thu, Apr 23, 2015 at 07:17:28AM -0700, Tony Lindgren wrote: > > > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [150423 03:26]: > > > > However, I don't think anyone is willing to say that they have a > > > > solution to this problem - obviously, you can't build OMAP as a > > > > non-multiplatform kernel anymore, so in effect you can never have > > > > the kernel enable this errata. And you can't detect whether you're > > > > running in secure mode or not. > > > > > > > > We could do the "only write the bit if it was originally clear" but > > > > we still have the problem that doing so may cause other people > > > > regressions. > > > > > > How about we keep the bit writing part !multiplatform conditional > > > (or even remove it) but always do the flush for ca-8? > > > > > > Then we could also do a warning for a misconfigured ca-8 later on. > > > > Yes, we could do this - we'll have to rely on the boot loader doing > > the right thing and setting this bit appropriately. For those > > platforms where this doesn't apply, I don't see any solution as (iirc) > > OMAP now requires MULTIPLATFORM to be enabled. > > OK, here's an updated patch. I've kept Sebastian's Tested-by as we know > the init part is a nop on n900 that he tested with. I've posted this updated version into Russell's patch system: http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=8353/1 Regards, Tony > 8< --------------------- > From: Tony Lindgren <tony@xxxxxxxxxxx> > Date: Mon, 27 Apr 2015 10:18:14 -0700 > Subject: [PATCH] ARM: mm: Fix Cortex-A8 erratum 430973 segfaults for bootloaders and multiarch > > Looks like apps can be made to segfault easily on armhf distros > just by running cpuburn-a8 in the background, then starting apt > get update unless erratum 430973 workaround is enabled. This happens > on r3p2 also, which has 430973 fixed in hardware. > > Turns out the reason for this is some bootloaders incorrectly > setting the auxilary register IBE bit, which probably causes us > to hit erratum 687067 on Cortex-A8 later than r1p2. > > If the bootloader incorrectly sets the IBE bit in the auxilary control > register for Cortex-A8 revisions with 430973 fixed in hardware, we > need to call flush BTAC/BTB to avoid segfaults probably caused by > erratum 687067. So let's flush BTAC/BTB unconditionally for Cortex-A8. > It won't do anything unless the IBE bit is set. > > Note that we keep the erratum 430973 Kconfig option still around and > disabled for multiarch as it may be unsafe to enable for some secure > SoC. It is known safe to be enabled for n900, but won't do anything > on n900 as the IBE bit needs to be set with SMC. > > Also note that SoCs probably should also add checks and print warnings > for the misconfigured IBE bit depending on the Cortex-A8 revision > so the bootloaders can be fixed Cortex-A8 revisions later than > r1p2 to not set the IBE bit. > > Tested-By: Sebastian Reichel <sre@xxxxxxxxxx> > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> > > --- a/arch/arm/mm/proc-v7-2level.S > +++ b/arch/arm/mm/proc-v7-2level.S > @@ -36,14 +36,16 @@ > * > * It is assumed that: > * - we are not using split page tables > + * > + * Note that we always need to flush BTAC/BTB if IBE is set > + * even on Cortex-A8 revisions not affected by 430973. > + * If IBE is not set, the flush BTAC/BTB won't do anything. > */ > ENTRY(cpu_ca8_switch_mm) > #ifdef CONFIG_MMU > mov r2, #0 > -#ifdef CONFIG_ARM_ERRATA_430973 > mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB > #endif > -#endif > ENTRY(cpu_v7_switch_mm) > #ifdef CONFIG_MMU > mmid r1, r1 @ get mm->context.id > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
