On 11/12, Shanker Donthineni wrote: > The ARM architecture defines the memory locations that are permitted > to be accessed as the result of a speculative instruction fetch from > an exception level for which all stages of translation are disabled. > Specifically, the core is permitted to speculatively fetch from the > 4KB region containing the current program counter 4K and next 4K. > > When translation is changed from enabled to disabled for the running > exception level (SCTLR_ELn[M] changed from a value of 1 to 0), the > Falkor core may errantly speculatively access memory locations outside > of the 4KB region permitted by the architecture. The errant memory > access may lead to one of the following unexpected behaviors. > > 1) A System Error Interrupt (SEI) being raised by the Falkor core due > to the errant memory access attempting to access a region of memory > that is protected by a slave-side memory protection unit. > 2) Unpredictable device behavior due to a speculative read from device > memory. This behavior may only occur if the instruction cache is > disabled prior to or coincident with translation being changed from > enabled to disabled. > > The conditions leading to this erratum will not occur when either of the > following occur: > 1) A higher exception level disables translation of a lower exception level > (e.g. EL2 changing SCTLR_EL1[M] from a value of 1 to 0). > 2) An exception level disabling its stage-1 translation if its stage-2 > translation is enabled (e.g. EL1 changing SCTLR_EL1[M] from a value of 1 > to 0 when HCR_EL2[VM] has a value of 1). > > To avoid the errant behavior, software must execute an ISB immediately > prior to executing the MSR that will change SCTLR_ELn[M] from 1 to 0. > This also applies to Kryo CPUs. I have a patch[1] for the 1003 Falkor errata that adds the Kryo MIDR check which can also be used for this errata. [1] https://patchwork.kernel.org/patch/10048987/ -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
