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Subject[PATCH 1/3] x86/fpu/xstate: Fix last_good_offset in setup_xstate_features()
Date
The function setup_xstate_features() uses CPUID to find each xfeature's
standard-format offset and size. Since XSAVES always uses the compacted
format, supervisor xstates are *NEVER* in the standard-format and their
offsets are left as -1's. However, they are still being tracked as
last_good_offset.

Fix it by tracking only user xstate offsets.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
---
arch/x86/kernel/fpu/xstate.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index a1806598aaa4..3ef3603bcfc5 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -265,22 +265,26 @@ static void __init setup_xstate_features(void)

cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);

+ xstate_sizes[i] = eax;
+
/*
* If an xfeature is supervisor state, the offset
* in EBX is invalid. We leave it to -1.
*/
- if (xfeature_is_user(i))
+ if (xfeature_is_user(i)) {
xstate_offsets[i] = ebx;

- xstate_sizes[i] = eax;
- /*
- * In our xstate size checks, we assume that the
- * highest-numbered xstate feature has the
- * highest offset in the buffer. Ensure it does.
- */
- WARN_ONCE(last_good_offset > xstate_offsets[i],
- "x86/fpu: misordered xstate at %d\n", last_good_offset);
- last_good_offset = xstate_offsets[i];
+ /*
+ * In our xstate size checks, we assume that the
+ * highest-numbered xstate feature has the
+ * highest offset in the buffer. Ensure it does.
+ */
+ WARN_ONCE(last_good_offset > xstate_offsets[i],
+ "x86/fpu: misordered xstate at %d\n",
+ last_good_offset);
+
+ last_good_offset = xstate_offsets[i];
+ }
}
}

--
2.21.0
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