With ARMv8.2-LVA and LPA architecture extensions, arm64 hardware which supports these extensions can support upto 52-bit virtual and 52-bit physical addresses respectively. Since at the moment we enable the support of these extensions via CONFIG flags, e.g. - LPA via CONFIG_ARM64_PA_BITS_52 there are no clear mechanisms in user-space right now to deteremine these CONFIG flag values and also determine the PARange and VARange address values. This patchset proposes two mechanisms to provide a user/user-space application more information on the same: 1. For a non-expert user, getting an idea about the virtual/physical address capabilities on an arm64 hardware via executing: $ cat /proc/cpuinfo can be quite useful as it provides a similar mechanism as available already on x86_64. PATCH 1/2 implements the same. 2. For a more involved user/user-space application, the Appendix I: Example in 'Documentation/arm64/cpu-feature-registers.txt' is pretty useful. If we can expose the PARange and VARange values via the MRS register reads to user-space, we can use them in user-space programs as a standard ABI. I already have a 'makedumpfile' user-space example that uses the same to determine ARMv8.2-LPA support. See [0]. PATCH 2/2 implements the same. [0]. https://github.com/bhupesh-sharma/makedumpfile/blob/9d7da4aad3efe79b448f48cc3454fcae46a316d6/arch/arm64.c#L499 Bhupesh Sharma (2): arm64: Expose address bits (physical/virtual) via cpuinfo arm64: Expose PARange via ID_AA64MMFR0_EL1 and VARange via ID_AA64MMFR2_EL1 arch/arm64/include/asm/cpufeature.h | 59 ++++++++++++++++++++++++------------- arch/arm64/include/asm/sysreg.h | 19 ++++++++++++ arch/arm64/kernel/cpufeature.c | 4 +-- arch/arm64/kernel/cpuinfo.c | 4 ++- 4 files changed, 63 insertions(+), 23 deletions(-) -- 2.7.4 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
