* 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. 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
