Re: [RFC PATCH for-4.22 2/2] tools: Introduce xen-inteltemp tool

[Jan Beulich <jbeulich@suse.com>]

On 27.10.2025 18:26, Teddy Astie wrote:
> Introduce a new tool to fetch Intel CPU temperatures through the
> Intel DTS interface using XENPF_resource_op hypercall.
> 
> Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
> ---
>  tools/misc/.gitignore      |  1 +
>  tools/misc/Makefile        |  4 ++
>  tools/misc/xen-inteltemp.c | 98 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 103 insertions(+)
>  create mode 100644 tools/misc/xen-inteltemp.c

Instead of introducing a new tool, might this not fit in xenpm?

> --- /dev/null
> +++ b/tools/misc/xen-inteltemp.c
> @@ -0,0 +1,98 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * xen-inteltemp.c
> + *
> + * Get the CPU temperature of Intel processors.
> + *
> + * Copyright 2025 Teddy Astie <teddy.astie@vates.tech>
> + */
> +
> +#include <stdio.h>
> +#include <errno.h>
> +#include <xenctrl.h>
> +
> +#define MSR_IA32_THERM_STATUS         0x0000019c
> +#define MSR_IA32_TEMPERATURE_TARGET   0x000001a2
> +#define MSR_IA32_PACKAGE_THERM_STATUS 0x000001b1
> +
> +int fetch_dts_temp(xc_interface *xch, uint32_t cpu, bool package, int *temp)
> +{
> +    xc_resource_entry_t entries[2] = {
> +        (xc_resource_entry_t){
> +            .idx = package ? MSR_IA32_PACKAGE_THERM_STATUS : MSR_IA32_THERM_STATUS
> +        },
> +        (xc_resource_entry_t){ .idx = MSR_IA32_TEMPERATURE_TARGET },
> +    };
> +    struct xc_resource_op ops = {
> +        .cpu = cpu,
> +        .entries = entries,
> +        .nr_entries = 2,
> +    };
> +    int tjmax;
> +
> +    int ret = xc_resource_op(xch, 1, &ops);
> +
> +    if ( ret <= 0 )
> +        /* This CPU isn't online or can't query this MSR */
> +        return ret ?: -EOPNOTSUPP;
> +
> +    if ( ret == 2 )
> +        tjmax = (entries[1].val >> 16) & 0xff;
> +    else
> +    {
> +        /*
> +         * The CPU doesn't support MSR_IA32_TEMPERATURE_TARGET, we assume it's 100 which
> +         * is correct aside a few selected Atom CPUs. Check coretemp source code for more
> +         * information.
> +         */
> +        fprintf(stderr, "CPU%d doesn't support MSR_IA32_TEMPERATURE_TARGET, assume "
> +               "tjmax=100°C, readings may be incorrect\n", cpu);
> +        tjmax = 100;
> +    }
> +    
> +    *temp = tjmax - ((entries[0].val >> 16) & 0xff);
> +    return 0;
> +}
> +
> +int main(void)
> +{
> +    int rc = 0, temp, cpu, socket;
> +    bool has_data = false;
> +    xc_interface *xch = xc_interface_open(0, 0, 0);
> +    xc_physinfo_t info;
> +
> +    if ( (rc = xc_physinfo(xch, &info)) < 0 )
> +    {
> +        perror("Getting physinfo failed");
> +        return rc;
> +    }
> +
> +    /* Per socket measurement */
> +    for ( socket = 0, cpu = 0;
> +          cpu < (info.max_cpu_id + 1);
> +          socket++, cpu += info.cores_per_socket * info.threads_per_core )
> +    {
> +        if ( !fetch_dts_temp(xch, cpu, true, &temp) )
> +        {
> +            has_data = true;
> +            printf("Package%d: %d°C\n", socket, temp);
> +        }
> +    }
> +
> +    printf("\n");
> +
> +    for ( cpu = 0; cpu < (info.max_cpu_id + 1); cpu += info.threads_per_core )
> +    {
> +        if ( fetch_dts_temp(xch, cpu, false, &temp) )
> +            continue;
> +
> +        has_data = true;
> +        printf("CPU%d: %d°C\n", cpu, temp);
> +    }
> +
> +    if ( !has_data )
> +        printf("No data\n");
> +
> +    xc_interface_close(xch);
> +    return 0;
> +}
> \ No newline at end of file

Please never introduce files without trailing newline.

Jan