Hi, On 28/01/2019 20:57, Bhupesh Sharma wrote:
ARMv8.2 architecture hardware extensions can support upto 52-bit physical addresses (ARMv8.2-LPA) and 52-bit virtual addresses (ARMv8.2-LVA). User-space utilities like 'makedumpfile' can try and use the getauxval() function to retrieve the underlying PARange and VARange values supported.
Why do we need VARange here ? This value could be different from the kernel VA. As for decoding the PTE, you could safely do the flip of the upper byte by checking the page size of 64K. What is the usecase for exposing the PARange ?
An example implementation can be via the 'Appendix I: Example' shown in 'Documentation/arm64/cpu-feature-registers.txt'. A reference 'makedumpfile' implementation which uses a similar approach is available in [0]. So, we expose these properties via 'FTR_NONSTRICT' and 'FTR_VISIBLE' settings for 'ID_AA64MMFR0_PARANGE_SHIFT' and 'ID_AA64MMFR2_LVA_SHIFT'.
What is the rationale behind changing the feature to NONSTRICT ?
[0]. https://github.com/bhupesh-sharma/makedumpfile/blob/9d7da4aad3efe79b448f48cc3454fcae46a316d6/arch/arm64.c#L499
Btw, if you are not using a 64K page size, the usage of the lva support feature could corrupt your PTE-> PHYS conversion, unless I am missing something. Suzuki _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
