Messages in this thread | | | Date | Tue, 8 Mar 2022 17:57:46 +0000 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH RFC] arm64: improve display about CPU architecture in cpuinfo |
| |
On Mon, Mar 07, 2022 at 08:05:06PM +0000, Robin Murphy wrote: > On 2022-03-07 19:30, Arnd Bergmann wrote: > > On Mon, Mar 7, 2022 at 5:48 PM Robin Murphy <robin.murphy@arm.com> wrote: > > > > > And arguably it's not even too late, because 10 years ago this *did* say > > > "AArch64". I don't remember all the exact details behind commit > > > 44b82b7700d0 ("arm64: Fix up /proc/cpuinfo") - this just tickled enough > > > of a memory to go and look up the git history - but I don't think we > > > changed any of those fields without a real reason. > > > > > > > The patch description does state that this was done for compatibility with > > 32-bit architectures, which does make some sense. I suppose for similar > > reasons, the arch/arm/ version of /proc/cpuinfo is now stuck at > > 'CPU architecture: 7', even for ARMv8 or higher in aarch32 mode. > > > > The part that I find more annoying is how we leave out the one bit > > of information that people are generally looking for in /proc/cpuinfo: > > the name of the processor. Even though we already know the > > exact processor type in order to handle the CPU errata, this is > > always "model name\t: ARMv7 Processor rev %d (v7l)" on 32-bit, > > and "model name\t: ARMv8 Processor rev %d (%s)" on 64-bit, > > with the revision being the least important bit of information here... > > Eh, it's hardly impossible to recompose a MIDR value from the implementer, > part, variant and revision fields if one actually needs to. Maybe we could > null-terminate the raw MIDR value and print it as a string of > largely-unprintable characters in the "model name" field... I guess that > might satisfy the crowd who want parity* with x86 CPUID, at least :)
Actually, it is impossible to do it reliably. I won't expand on this, except what I said in my other reply - there are cases where the MIDR value is not unique.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
| |