[PATCH 8/9] x86, xsave: add support for non-lazy xstates

[Hans Rosenfeld <hans.rosenfeld@amd.com>]

Non-lazy xstates are, as the name suggests, extended states that cannot
be saved or restored lazily. The state for AMDs LWP feature is a
non-lazy state.

This patch adds support for this kind of xstates. If any such states are
present and supported on the running system, they will always be enabled
in xstate_mask so that they are always restored in switch_to.

Signed-off-by: Hans Rosenfeld <hans.rosenfeld@amd.com>
---
 arch/x86/include/asm/xsave.h |    5 +++--
 arch/x86/kernel/xsave.c      |    6 +++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index 12793b6..02f1e1d 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -23,9 +23,10 @@
 /*
  * These are the features that the OS can handle currently.
  */
-#define XCNTXT_MASK	(XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
+#define XCNTXT_LAZY	(XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
+#define XCNTXT_NONLAZY	0
 
-#define XCNTXT_LAZY	XCNTXT_MASK
+#define XCNTXT_MASK	(XCNTXT_LAZY | XCNTXT_NONLAZY)
 
 #ifdef CONFIG_X86_64
 #define REX_PREFIX	"0x48, "
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 1a11291..988bdef 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -16,6 +16,7 @@
  * Supported feature mask by the CPU and the kernel.
  */
 u64 pcntxt_mask;
+EXPORT_SYMBOL(pcntxt_mask);
 
 /*
  * Represents init state for the supported extended state.
@@ -261,7 +262,7 @@ int restore_xstates_sigframe(void __user *buf, unsigned int size)
 	struct task_struct *tsk = current;
 	struct _fpstate_ia32 __user *fp = buf;
 	struct xsave_struct *xsave;
-	u64 xstate_mask = 0;
+	u64 xstate_mask = pcntxt_mask & XCNTXT_NONLAZY;
 
 	if (!buf) {
 		if (used_math()) {
@@ -478,6 +479,9 @@ static void __init xstate_enable_boot_cpu(void)
 	printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
 	       "cntxt size 0x%x\n",
 	       pcntxt_mask, xstate_size);
+
+	if (pcntxt_mask & XCNTXT_NONLAZY)
+		task_thread_info(&init_task)->xstate_mask |= XCNTXT_NONLAZY;
 }
 
 /*
-- 
1.7.5.4