Re: [PATCH 6/7] target/i386: implement RDPID in TCG

[Richard Henderson <richard.henderson@linaro.org>]

On 6/18/23 23:51, Paolo Bonzini wrote:
> RDPID corresponds to a RDMSR(TSC_AUX); however, it is unprivileged
> so for user-mode emulation we must provide the value that the kernel
> places in the MSR.  For Linux, it is a combination of the current CPU
> and the current NUMA node, both of which can be retrieved with getcpu(2).
> For BSD, just return 0.
> 
> RDTSCP is reimplemented as RDTSC + RDPID ECX; the differences in terms
> of serializability are not relevant to QEMU.
> 
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
> ---
>   linux-user/i386/target_cpu.h   |  8 ++++++++
>   linux-user/x86_64/target_cpu.h |  1 +
>   target/i386/cpu.c              | 10 +++++++++-
>   target/i386/helper.h           |  2 +-
>   target/i386/tcg/misc_helper.c  | 21 +++++++++++++++------
>   target/i386/tcg/translate.c    | 15 +++++++++++++--
>   6 files changed, 47 insertions(+), 10 deletions(-)
> 
> diff --git a/linux-user/i386/target_cpu.h b/linux-user/i386/target_cpu.h
> index 52caf788cc3..3539f790222 100644
> --- a/linux-user/i386/target_cpu.h
> +++ b/linux-user/i386/target_cpu.h
> @@ -54,4 +54,12 @@ static inline abi_ulong get_sp_from_cpustate(CPUX86State *state)
>   {
>       return state->regs[R_ESP];
>   }
> +
> +static inline uint32_t get_cpunode(void)
> +{
> +    unsigned cpu, node;
> +    getcpu(&cpu, &node);
> +    return (node << 12) | (cpu & 0xfff);
> +}
> +

What is our minimum glibc version?  This requires 2.29.

Also, not especially fond of the placement.  target/ including linux-user/ header isn't 
nice.  Might as well just place these 3 lines in misc_helper.c to begin.

r~