| Message ID | 81f4c402d1fda7c2419aac1148061a0789112e76.1749849645.git.calvin@wbinvd.org |
|---|---|
| State | New |
| Headers | show |
| Series | tools/power turbostat: Fix MSRs with CONFIG_MULTIUSER=n | expand |
On Monday 06/16 at 01:30 +0000, Zhang, Rui wrote: > On Fri, 2025-06-13 at 19:20 -0700, Calvin Owens wrote: > > Handle ENOSYS from cap_get_proc() in check_for_cap_sys_rawio(), so > > turbostat can display temperatures when running on kernels compiled > > without multiuser support. > > > > Signed-off-by: Calvin Owens <calvin@wbinvd.org> > > --- > > tools/power/x86/turbostat/turbostat.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/tools/power/x86/turbostat/turbostat.c > > b/tools/power/x86/turbostat/turbostat.c > > index 925556b90770..f7d665913a52 100644 > > --- a/tools/power/x86/turbostat/turbostat.c > > +++ b/tools/power/x86/turbostat/turbostat.c > > @@ -6496,8 +6496,13 @@ int check_for_cap_sys_rawio(void) > > int ret = 0; > > > > caps = cap_get_proc(); > > - if (caps == NULL) > > + if (caps == NULL) { > > + /* Support CONFIG_MULTIUSER=n */ > > + if (errno == ENOSYS) > > Can you point me where this knowledge comes from? > > I downloaded the libcap source and didn't see how ENOSYS is set. Hi Rui, When the kernel is built without multiuser support, the capget() et al. syscalls are #ifdef'd out: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/capability.c#n32 ...so userspace will get -ENOSYS when it tries to call them, and that ends up being propagated to errno in userspace. Admittedly it is sort of implicit. Maybe a better way to "fix" this would be to warn the user if the capability check fails, but still attempt to access the MSR devices? I can do that if you prefer. That is my only problem here: when check_for_cap_sys_rawio() fails, the current code doesn't attempt to access the MSR devices at all, even though in my case it would actually work. I realize this is very weird: it came up when I was recently including turbostat as part of an extremely tiny bootable utility image. Thanks, Calvin > thanks, > rui > > + return 0; > > + > > return 1; > > + } > > > > if (cap_get_flag(caps, CAP_SYS_RAWIO, CAP_EFFECTIVE, > > &cap_flag_value)) { > > ret = 1; >
diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c index 925556b90770..f7d665913a52 100644 --- a/tools/power/x86/turbostat/turbostat.c +++ b/tools/power/x86/turbostat/turbostat.c @@ -6496,8 +6496,13 @@ int check_for_cap_sys_rawio(void) int ret = 0; caps = cap_get_proc(); - if (caps == NULL) + if (caps == NULL) { + /* Support CONFIG_MULTIUSER=n */ + if (errno == ENOSYS) + return 0; + return 1; + } if (cap_get_flag(caps, CAP_SYS_RAWIO, CAP_EFFECTIVE, &cap_flag_value)) { ret = 1;
Handle ENOSYS from cap_get_proc() in check_for_cap_sys_rawio(), so turbostat can display temperatures when running on kernels compiled without multiuser support. Signed-off-by: Calvin Owens <calvin@wbinvd.org> --- tools/power/x86/turbostat/turbostat.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)