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x86/cpu: Log CPU flag cmdline hacks more verbosely

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Since using these options is very dangerous, make details as visible as
possible:

- Instead of a single message for each of the cmdline options, print a
  separate pr_warn() for each individual flag.

- Say explicitly whether the flag is a "feature" or a "bug".

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250303-setcpuid-taint-louder-v1-3-8d255032cb4c@google.com
This commit is contained in:
Brendan Jackman 2025-03-03 15:45:39 +00:00 committed by Ingo Molnar
parent 681955761b
commit d0ba9bcf00
1 changed files with 23 additions and 16 deletions
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39
arch/x86/kernel/cpu/common.c
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@ -1484,8 +1484,6 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
char *opt;
int taint = 0;
pr_warn("%s CPUID bits:", set ? "Force-enabling" : "Clearing");
while (arg) {
bool found __maybe_unused = false;
unsigned int bit;
@ -1500,16 +1498,19 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
if (!kstrtouint(opt, 10, &bit)) {
if (bit < NCAPINTS * 32) {
if (set) {
pr_warn("setcpuid: force-enabling CPU feature flag:");
setup_force_cpu_cap(bit);
} else {
pr_warn("clearcpuid: force-disabling CPU feature flag:");
setup_clear_cpu_cap(bit);
}
/* empty-string, i.e., ""-defined feature flags */
if (!x86_cap_flags[bit])
pr_cont(" %d:%d", bit >> 5, bit & 31);
pr_cont(" %d:%d\n", bit >> 5, bit & 31);
else
pr_cont(" %s", x86_cap_flags[bit]);
pr_cont(" %s\n", x86_cap_flags[bit]);
if (set)
setup_force_cpu_cap(bit);
else
setup_clear_cpu_cap(bit);
taint++;
}
/*
@ -1521,11 +1522,15 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
for (bit = 0; bit < 32 * (NCAPINTS + NBUGINTS); bit++) {
const char *flag;
const char *kind;
if (bit < 32 * NCAPINTS)
if (bit < 32 * NCAPINTS) {
flag = x86_cap_flags[bit];
else
kind = "feature";
} else {
kind = "bug";
flag = x86_bug_flags[bit - (32 * NCAPINTS)];
}
if (!flag)
continue;
@ -1533,22 +1538,24 @@ static inline bool parse_set_clear_cpuid(char *arg, bool set)
if (strcmp(flag, opt))
continue;
pr_cont(" %s", opt);
if (set)
if (set) {
pr_warn("setcpuid: force-enabling CPU %s flag: %s\n",
kind, flag);
setup_force_cpu_cap(bit);
else
} else {
pr_warn("clearcpuid: force-disabling CPU %s flag: %s\n",
kind, flag);
setup_clear_cpu_cap(bit);
}
taint++;
found = true;
break;
}
if (!found)
pr_cont(" (unknown: %s)", opt);
pr_warn("%s: unknown CPU flag: %s", set ? "setcpuid" : "clearcpuid", opt);
}
pr_cont("\n");
return taint;
}