arm64: Fix TTBR + PAN + 52-bit PA logic in cpu_do_switch_mm
In cpu_do_switch_mm(.) with ARM64_SW_TTBR0_PAN=y we apply phys_to_ttbr
to a value that already has an ASID inserted into the upper bits. For
52-bit PA configurations this then can give us TTBR0_EL1 registers that
cause translation table walks to attempt to access non-zero PA[51:48]
spuriously. Ultimately leading to a Synchronous External Abort on level
1 translation.
This patch re-arranges the logic in cpu_do_switch_mm(.) such that
phys_to_ttbr is called before the ASID is inserted into the TTBR0 value.
Fixes: 6b88a32c7af6 ("arm64: kpti: Fix the interaction between ASID switching and software PAN")
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Kristina Martsenko <kristina.martsenko@arm.com>
Reviewed-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index c6a1207..9f177aa 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -153,14 +153,14 @@
ENTRY(cpu_do_switch_mm)
mrs x2, ttbr1_el1
mmid x1, x1 // get mm->context.id
+ phys_to_ttbr x0, x3
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
- bfi x0, x1, #48, #16 // set the ASID field in TTBR0
+ bfi x3, x1, #48, #16 // set the ASID field in TTBR0
#endif
bfi x2, x1, #48, #16 // set the ASID
msr ttbr1_el1, x2 // in TTBR1 (since TCR.A1 is set)
isb
- phys_to_ttbr x0, x2
- msr ttbr0_el1, x2 // now update TTBR0
+ msr ttbr0_el1, x3 // now update TTBR0
isb
b post_ttbr_update_workaround // Back to C code...
ENDPROC(cpu_do_switch_mm)