[PATCH] arm64: cpu_errata: Add Kryo to Falkor 1003 errata

On 11/14, Stephen Boyd wrote:

On 11/10, Catalin Marinas wrote:

quoted

On Wed, Nov 08, 2017 at 11:00:29AM -0800, Stephen Boyd wrote:

quoted

The Kryo CPUs are also affected by the Falkor 1003 errata, so
we need to do the same workaround on Kryo CPUs. The MIDR is
slightly more complicated here, where the PART number is not
always the same when looking at all the bits from 15 to 4. Drop
the lower 8 bits and just look at the top 4 to see if it's '2'
and then consider those as Kryo CPUs. This covers all the
combinations without having to list them all out.

Signed-off-by: Stephen Boyd <redacted>
---

We may need to introduce another Kconfig option to block software PAN
from being enabled when this errata is enabled (and then have software PAN
depend on this new config being false).

It depends on whether you'd want to use SW PAN together with these CPUs.
From a defconfig + single Image perspective, SW PAN is disabled but it
would be nice to allow single Image with both E1003 and SW PAN configs
enabled (though SW PAN wouldn't be used at run-time).

As a quick hack, something like below but we may want to add a separate
cap bit as a minor optimisation (not sure it makes a difference).
Untested:

Ok. The Falkor CPUs support HW PAN so your patch looks like it
should work. If we're running on a Kryo CPU we may not see the HW
PAN capability and then we would still return false here because
the errata is present. I'll fold it in and test it out.

Almost works. The problem is that uaccess_ttbr0_{disable,enable}
assembly macros need to be patched for NOPs if we have cap bits
for ARM64_HAS_PAN or ARM64_WORKAROUND_QCOM_FALKOR_E1003. From
what I can tell, we have only ever had one bit there so doing
something like:

----8<----

diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index b3da6c886835..70644cde9e7c 100644
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h

@@ -26,13 +26,13 @@
 	.endm
 
 	.macro	uaccess_ttbr0_disable, tmp1
-alternative_if_not ARM64_HAS_PAN
+alternative_if_not (ARM64_HAS_PAN | ARM64_WORKAROUND_QCOM_FALKOR_E1003)
 	__uaccess_ttbr0_disable \tmp1
 alternative_else_nop_endif
 	.endm
 
 	.macro	uaccess_ttbr0_enable, tmp1, tmp2
-alternative_if_not ARM64_HAS_PAN
+alternative_if_not (ARM64_HAS_PAN | ARM64_WORKAROUND_QCOM_FALKOR_E1003)
 	save_and_disable_irq \tmp2		// avoid preemption
 	__uaccess_ttbr0_enable \tmp1
 	restore_irq \tmp2

won't work just like that because it's not a bitmask, just a raw
cap number. So I need to introduce another capability number that
combines the presence of HW_PAN and this errata? Looks like it
would be similar to ARM64_ALT_PAN_NOT_UAO.

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