On 10/21/20 12:46, Marc Zyngier wrote: > On 2020-10-21 12:25, Greg Kroah-Hartman wrote: > > On Wed, Oct 21, 2020 at 12:09:58PM +0100, Marc Zyngier wrote: > > > On 2020-10-21 11:46, Qais Yousef wrote: > > > > So that userspace can detect if the cpu has aarch32 support at EL0. > > > > > > > > CPUREGS_ATTR_RO() was renamed to CPUREGS_RAW_ATTR_RO() to better reflect > > > > what it does. And fixed to accept both u64 and u32 without causing the > > > > printf to print out a warning about mismatched type. This was caught > > > > while testing to check the new CPUREGS_USER_ATTR_RO(). > > > > > > > > The new CPUREGS_USER_ATTR_RO() exports a Sanitised or RAW sys_reg based > > > > on a @cond to user space. The exported fields match the definition in > > > > arm64_ftr_reg so that the content of a register exported via MRS and > > > > sysfs are kept cohesive. > > > > > > > > The @cond in our case is that the system is asymmetric aarch32 and the > > > > controlling sysctl.enable_asym_32bit is enabled. > > > > > > > > Update Documentation/arm64/cpu-feature-registers.rst to reflect the > > > > newly visible EL0 field in ID_AA64FPR0_EL1. > > > > > > > > Note that the MRS interface will still return the sanitized content > > > > _only_. > > > > > > > > Signed-off-by: Qais Yousef <qais.yousef@xxxxxxx> > > > > --- > > > > > > > > Example output. I was surprised that the 2nd field (bits[7:4]) is > > > > printed out > > > > although it's set as FTR_HIDDEN. > > > > > > > > # cat /sys/devices/system/cpu/cpu*/regs/identification/id_aa64pfr0 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > > > > > # echo 1 > /proc/sys/kernel/enable_asym_32bit > > > > > > > > # cat /sys/devices/system/cpu/cpu*/regs/identification/id_aa64pfr0 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > 0x0000000000000012 > > > > 0x0000000000000012 > > > > 0x0000000000000011 > > > > 0x0000000000000011 > > > > > > This looks like a terrible userspace interface. > > > > It's also not allowed, sorry. sysfs is "one value per file", which is > > NOT what is happening at all. > > I *think* Qais got that part right, though it is hard to tell without > knowing how many CPUs this system has (cpu/cpu* is ambiguous). Correct. This interface already exists for other registers and reads a single value for each CPU. I just added the ability to read a new register. Though it has a slightly different behavior: reads Sanitized vs RAW info. Thanks -- Qais Yousef
