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Subject[PATCH v2 1/3] x86/fpu/xstate: Fix small issues before adding supervisor xstates
Date
In response to earlier comments, fix small issues before introducing XSAVES
supervisor states:
- Fix comments of xfeature_is_supervisor().
- Replace ((u64)1 << 63) with XCOMP_BV_COMPACTED_FORMAT.

No functional changes from this patch.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/fpu/xstate.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 319be936c348..0bd313351650 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -110,12 +110,9 @@ EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
static int xfeature_is_supervisor(int xfeature_nr)
{
/*
- * We currently do not support supervisor states, but if
- * we did, we could find out like this.
- *
- * SDM says: If state component 'i' is a user state component,
- * ECX[0] return 0; if state component i is a supervisor
- * state component, ECX[0] returns 1.
+ * Extended State Enumeration Sub-leaves (EAX = 0DH, ECX = n, n > 1)
+ * returns ECX[0] set to (1) for a supervisor state, and cleared (0)
+ * for a user state.
*/
u32 eax, ebx, ecx, edx;

@@ -419,7 +416,8 @@ static void __init setup_init_fpu_buf(void)
print_xstate_features();

if (boot_cpu_has(X86_FEATURE_XSAVES))
- init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
+ init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
+ xfeatures_mask;

/*
* Init all the features state with header.xfeatures being 0x0
--
2.17.1
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