[libvirt PATCH] util: Fix getting CPU frequency on Apple Silicon

The hw.cpufrequency sysctl, which we use to obtain the CPU frequency on macOS, is not available when running on Apple Silicon, and as a consequence we currently report an error whenever such information is requested. The virNodeInfo.mhz field, where the CPU frequency gets stored, is documented as being zero when the information could not be obtained, and we already do that for Linux on aarch64. Extend this behavior to macOS on Apple Silicon. Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- src/util/virhostcpu.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c index a07c00a0e9..011ef8a153 100644 --- a/src/util/virhostcpu.c +++ b/src/util/virhostcpu.c @@ -928,8 +928,14 @@ virHostCPUGetInfo(virArch hostarch G_GNUC_UNUSED, *mhz = cpu_freq; # else if (sysctlbyname("hw.cpufrequency", &cpu_freq, &cpu_freq_len, NULL, 0) < 0) { - virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); - return -1; + if (errno == ENOENT) { + /* The hw.cpufrequency sysctl is not implemented on Apple Silicon. + * In that case, we report 0 instead of erroring out */ + cpu_freq = 0; + } else { + virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); + return -1; + } } *mhz = cpu_freq / 1000000; -- 2.34.1

On 2/10/22 10:08, Andrea Bolognani wrote:
The hw.cpufrequency sysctl, which we use to obtain the CPU frequency on macOS, is not available when running on Apple Silicon, and as a consequence we currently report an error whenever such information is requested.
The virNodeInfo.mhz field, where the CPU frequency gets stored, is documented as being zero when the information could not be obtained, and we already do that for Linux on aarch64. Extend this behavior to macOS on Apple Silicon.
Signed-off-by: Andrea Bolognani <abologna@redhat.com> --- src/util/virhostcpu.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
Reviewed-by: Michal Privoznik <mprivozn@redhat.com> Michal

On Thu, Feb 10, 2022 at 10:08:42AM +0100, Andrea Bolognani wrote:
+++ b/src/util/virhostcpu.c @@ -928,8 +928,14 @@ virHostCPUGetInfo(virArch hostarch G_GNUC_UNUSED, *mhz = cpu_freq; # else if (sysctlbyname("hw.cpufrequency", &cpu_freq, &cpu_freq_len, NULL, 0) < 0) { - virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); - return -1; + if (errno == ENOENT) { + /* The hw.cpufrequency sysctl is not implemented on Apple Silicon. + * In that case, we report 0 instead of erroring out */ + cpu_freq = 0; + } else { + virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); + return -1; + } }
Menci, can you please confirm this works for you before I push? I have no way of verifying that on my own. Thanks! -- Andrea Bolognani / Red Hat / Virtualization

I tested the patch (applying to v7.10.0) and it works on my M1 MacBook Air. Thanks. On Sat, Feb 12, 2022 at 1:32 AM Andrea Bolognani <abologna@redhat.com> wrote:
+++ b/src/util/virhostcpu.c @@ -928,8 +928,14 @@ virHostCPUGetInfo(virArch hostarch G_GNUC_UNUSED, *mhz = cpu_freq; # else if (sysctlbyname("hw.cpufrequency", &cpu_freq, &cpu_freq_len, NULL,
On Thu, Feb 10, 2022 at 10:08:42AM +0100, Andrea Bolognani wrote: 0) < 0) {
- virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); - return -1; + if (errno == ENOENT) { + /* The hw.cpufrequency sysctl is not implemented on Apple Silicon. + * In that case, we report 0 instead of erroring out */ + cpu_freq = 0; + } else { + virReportSystemError(errno, "%s", _("cannot obtain CPU freq")); + return -1; + } }
Menci, can you please confirm this works for you before I push? I have no way of verifying that on my own. Thanks!
-- Andrea Bolognani / Red Hat / Virtualization
participants (3)
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Andrea Bolognani
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Menci
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Michal Prívozník