We did not handle XSAVES instructions correctly. There were issues in
converting between standard and compacted format when interfacing with
user-space. These issues have been corrected.
Add a WARN_ONCE() to make it clear that XSAVES supervisor states are not
yet implemented.
Signed-off-by: Yu-cheng Yu <yu-cheng...@intel.com>
Reviewed-by: Dave Hansen <dave.han...@intel.com>
---
arch/x86/kernel/fpu/init.c | 15 ---------------
arch/x86/kernel/fpu/xstate.c | 10 ++++++++++
2 files changed, 10 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index eccc36b..2b4f871 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -230,21 +230,6 @@ static void __init
fpu__init_system_xstate_size_legacy(void)
}
fpu_user_xstate_size = fpu_kernel_xstate_size;
-
- /*
- * Quirk: we don't yet handle the XSAVES* instructions
- * correctly, as we don't correctly convert between
- * standard and compacted format when interfacing
- * with user-space - so disable it for now.
- *
- * The difference is small: with recent CPUs the
- * compacted format is only marginally smaller than
- * the standard FPU state format.
- *
- * ( This is easy to backport while we are fixing
- * XSAVES* support. )
- */
- setup_clear_cpu_cap(X86_FEATURE_XSAVES);
}
/*
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 7c2cdc4..fed95f5 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -222,6 +222,16 @@ void fpu__init_cpu_xstate(void)
if (!cpu_has_xsave || !xfeatures_mask)
return;
+ /*
+ * Make it clear that XSAVES supervisor states are not yet
+ * implemented should anyone expect it to work by changing
+ * bits in XFEATURE_MASK_* macros and XCR0.
+ */
+ WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
+ "x86/fpu: XSAVES supervisor states are not yet implemented.\n");
+
+ xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;
+
cr4_set_bits(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}
--
1.9.1
