Re: [PATCH] linux-user: Emulate /proc/cpuinfo on aarch64 and arm

[Peter Maydell]

On Tue, 1 Aug 2023 at 15:41, Helge Deller <deller@gmx.de> wrote:
>
> On 8/1/23 16:22, Peter Maydell wrote:
> > On Tue, 1 Aug 2023 at 14:57, Helge Deller <deller@gmx.de> wrote:
> >>
> >> Add emulation for /proc/cpuinfo for arm architecture.
> >> The output below mimics output as seen on debian porterboxes.
> >
> >
> >> +#if defined(TARGET_AARCH64) || defined(TARGET_ARM)
> >> +static int open_cpuinfo(CPUArchState *cpu_env, int fd)
> >> +{
> >> +    int i, num_cpus;
> >> +    const int is64 = TARGET_ABI_BITS == 64;
> >> +
> >> +    num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> >> +    for (i = 0; i < num_cpus; i++) {
> >> +        dprintf(fd, "processor\t: %d\n", i);
> >> +        if (!is64) {
> >> +            dprintf(fd, "model name\t: ARMv7 Processor rev 2 (v7l)\n");
> >> +        }
> >> +        dprintf(fd, "BogoMIPS\t: %d.00\n", is64 ? 100 : 50);
> >> +        dprintf(fd, "Features\t: %s\n",
> >> +                is64 ? "fp asimd evtstrm cpuid"
> >> +                     : "half thumb fastmult vfp edsp thumbee vfpv3 " \
> >> +                       "tls idiva idivt vfpd32 lpae");
> >> +        dprintf(fd, "CPU implementer\t: 0x%d\n", is64 ? 50 : 56);
> >> +        dprintf(fd, "CPU architecture: %d\n",    is64 ? 8 : 7);
> >> +        dprintf(fd, "CPU variant\t: 0x%d\n",     is64 ? 0 : 2);
> >> +        dprintf(fd, "CPU part\t: 0x%d\n",        is64 ? 0 : 584);
> >> +        dprintf(fd, "CPU revision\t: %d\n\n",    is64 ? 1 : 2);
> >
> > If you want to do this you should hook it up to what the
> > CPU being emulated actually is and what features it has.
> > (Compare how we set the hwcaps.)
>
> Nice!
> I didn't know about those elf hwcaps...

In an ideal world guest code should only look at the
hwcaps (which are the ABI-stable interface the kernel
provides), not at what's in /proc/cpuinfo. But of
course if you're a shell script then cpuinfo is a lot
easier to deal with...

thanks
-- PMM