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>
---
arch/x86/kernel/fpu/init.c | 16 ++++------------
arch/x86/kernel/fpu/xstate.c | 8 ++++++++
2 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index b5952d5..21e0d52 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -228,19 +228,11 @@ static void __init
fpu__init_system_xstate_size_legacy(void)
user_xstate_size = 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. )
+ * Most recent CPUs supporting XSAVES can run 64-bit mode.
+ * Enable XSAVES for 64-bit.
*/
- setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+ if (!config_enabled(CONFIG_X86_64))
+ setup_clear_cpu_cap(X86_FEATURE_XSAVES);
}
/*
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 2e80d6f..cb2a484 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -204,6 +204,14 @@ 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");
+
cr4_set_bits(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
}
--
1.9.1
