[PATCH v12 4/4] x86/cpu: Clear feature bits whose dependencies were cleared

[Maciej Wieczor-Retman]

From: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>

After cpu_caps_cleared[] is initialized with DISABLED_MASK_INIT,
features present in disabled bitmasks are cleared from x86_capability[].
However features that depend on them and are not part of any disabled
mask are not cleared by anything. They can trigger the warning in
check_cpufeature_deps(), as before both features would show up as
enabled even though they weren't. The uncleared features can also still
falsely show up in /proc/cpuinfo.

Take such cases into account before applying the cpu_caps_cleared[]
array.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
---
Changelog v12:
- Move the check from check_cpufeature_deps() to apply_forced_caps().
  Redo last paragraph of the patch message.

Changelog v11:
- Add this patch to the series.

 arch/x86/include/asm/cpufeature.h |  1 +
 arch/x86/kernel/cpu/common.c      |  2 ++
 arch/x86/kernel/cpu/cpuid-deps.c  | 14 ++++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 3ddc1d33399b..e7a62990a9c2 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -77,6 +77,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 
 extern void setup_clear_cpu_cap(unsigned int bit);
 extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
+void clear_feature_disabled_deps(struct cpuinfo_x86 *c);
 void check_cpufeature_deps(struct cpuinfo_x86 *c);
 
 #define setup_force_cpu_cap(bit) do {			\
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8ad0da7012dd..2e24bdb3acaa 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -955,6 +955,8 @@ static void apply_forced_caps(struct cpuinfo_x86 *c)
 {
 	int i;
 
+	clear_feature_disabled_deps(c);
+
 	for (i = 0; i < NCAPINTS + NBUGINTS; i++) {
 		c->x86_capability[i] &= ~cpu_caps_cleared[i];
 		c->x86_capability[i] |= cpu_caps_set[i];
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 4354c0dd6d66..83060c0013c1 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -158,6 +158,20 @@ void setup_clear_cpu_cap(unsigned int feature)
 	do_clear_cpu_cap(NULL, feature);
 }
 
+/*
+ * If the dependency was cleared through the disabled bitmasks while the
+ * feature wasn't it also needs to be cleared.
+ */
+void clear_feature_disabled_deps(struct cpuinfo_x86 *c)
+{
+	const struct cpuid_dep *d;
+
+	for (d = cpuid_deps; d->feature; d++) {
+		if (!DISABLED_MASK_BIT_SET(d->feature) && DISABLED_MASK_BIT_SET(d->depends))
+			set_bit(d->feature, (unsigned long *)cpu_caps_cleared);
+	}
+}
+
 void check_cpufeature_deps(struct cpuinfo_x86 *c)
 {
 	char feature_buf[X86_NAMELESS_FEAT_BUFLEN], depends_buf[X86_NAMELESS_FEAT_BUFLEN];
-- 
2.53.0