[v4,09/26] xen/x86: Clear dependent features when clearing a cpu cap

Commit Message

Andrew Cooper March 23, 2016, 4:36 p.m. UTC

When clearing a cpu cap, clear all dependent features.  This avoids having a
featureset with intermediate features disabled, but leaf features enabled.

Signed-off-by: Andrew Cooper <[e-mail]>
Reviewed-by: Jan Beulich <[e-mail]>
---
v3:
 * Style fixes.  Use __test_and_set_bit()
---
 xen/arch/x86/cpu/common.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

Patch

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index d302272..0942b44 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -53,8 +53,22 @@  static unsigned int cleared_caps[NCAPINTS];
 
 void __init setup_clear_cpu_cap(unsigned int cap)
 {
+	const uint32_t *dfs;
+	unsigned int i;
+
+	if (__test_and_set_bit(cap, cleared_caps))
+		return;
+
 	__clear_bit(cap, boot_cpu_data.x86_capability);
-	__set_bit(cap, cleared_caps);
+	dfs = lookup_deep_deps(cap);
+
+	if (!dfs)
+		return;
+
+	for (i = 0; i < FSCAPINTS; ++i) {
+		cleared_caps[i] |= dfs[i];
+		boot_cpu_data.x86_capability[i] &= ~dfs[i];
+	}
 }
 
 static void default_init(struct cpuinfo_x86 * c)