x86/fpu: Generalize 'init_xstate_ctx'

So the handling of init_xstate_ctx has a layering violation: both
'struct xsave_struct' and 'union thread_xstate' have a
'struct i387_fxsave_struct' member:

   xsave_struct::i387
   thread_xstate::fxsave

The handling of init_xstate_ctx is generic, it is used on all
CPUs, with or without XSAVE instruction. So it's confusing how
the generic code passes around and handles an XSAVE specific
format.

What we really want is for init_xstate_ctx to be a proper
fpstate and we use its ::fxsave and ::xsave members, as
appropriate.

Since the xsave_struct::i387 and thread_xstate::fxsave aliases
each other this is not a functional problem.

So implement this, and move init_xstate_ctx to the generic FPU
code in the process.

Also, since init_xstate_ctx is not XSAVE specific anymore,
rename it to init_fpstate, and mark it __read_mostly,
because it's only modified once during bootup, and used
as a reference fpstate later on.

There's no change in functionality.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index b74aa4329aeb0a77213c7c4c0d54675ac118c5e3..792fdbe64179ca596d7f239068e734559e406238 100644 (file)
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -22,6 +22,8 @@
 
 extern unsigned int mxcsr_feature_mask;
 
+extern union thread_xstate init_fpstate;
+
 extern void fpu__init_cpu(void);
 extern void fpu__init_system_xstate(void);
 extern void fpu__init_cpu_xstate(void);
@@ -342,9 +344,9 @@ static inline void fpregs_deactivate(struct fpu *fpu)
 static inline void restore_init_xstate(void)
 {
        if (use_xsave())
-               xrstor_state(&init_xstate_ctx, -1);
+               xrstor_state(&init_fpstate.xsave, -1);
        else
-               fxrstor_checking(&init_xstate_ctx.i387);
+               fxrstor_checking(&init_fpstate.fxsave);
 }
 
 /*

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index afd21329c5858dd31e1d3691bda47df2e407acc2..3051280887b833bc5691c78645411a7ee17eaa5d 100644 (file)
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -37,7 +37,6 @@
 extern unsigned int xstate_size;
 extern u64 xfeatures_mask;
 extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
-extern struct xsave_struct init_xstate_ctx;
 
 extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask);
 

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 8e4cad57be3df726a572df53dce1ec63e64337d3..a396f80b771f581aac1cd772e26cdf1df43c7fe9 100644 (file)
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -12,6 +12,12 @@
 
 #include <linux/hardirq.h>
 
+/*
+ * Represents the initial FPU state. It's mostly (but not completely) zeroes,
+ * depending on the FPU hardware format:
+ */
+union thread_xstate init_fpstate __read_mostly;
+
 /*
  * Track whether the kernel is using the FPU state
  * currently.

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 5a7e570789351f8965c3858a8c2c2899a4abe391..93bc11a5812c5e7cd1a54cf21b7adabef96f1ea6 100644 (file)
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -121,7 +121,7 @@ static void fpu__init_system_generic(void)
         * Set up the legacy init FPU context. (xstate init might overwrite this
         * with a more modern format, if the CPU supports it.)
         */
-       fpstate_init_fxstate(&init_xstate_ctx.i387);
+       fpstate_init_fxstate(&init_fpstate.fxsave);
 
        fpu__init_system_mxcsr();
 }

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index afbd5827743095504f10ab5c82d7181e8a8e139f..527d4bf4f3044c745fa6038d8a68219793daeea2 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -31,11 +31,6 @@ static const char *xfeature_names[] =
  */
 u64 xfeatures_mask __read_mostly;
 
-/*
- * Represents init state for the supported extended state.
- */
-struct xsave_struct init_xstate_ctx;
-
 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
 static unsigned int xstate_offsets[XFEATURES_NR_MAX], xstate_sizes[XFEATURES_NR_MAX];
 static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
@@ -150,7 +145,7 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
                        int size = xstate_sizes[feature_bit];
 
                        memcpy((void *)fx + offset,
-                              (void *)&init_xstate_ctx + offset,
+                              (void *)&init_fpstate.xsave + offset,
                               size);
                }
 
@@ -377,12 +372,12 @@ static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only)
        if (use_xsave()) {
                if ((unsigned long)buf % 64 || fx_only) {
                        u64 init_bv = xfeatures_mask & ~XSTATE_FPSSE;
-                       xrstor_state(&init_xstate_ctx, init_bv);
+                       xrstor_state(&init_fpstate.xsave, init_bv);
                        return fxrstor_user(buf);
                } else {
                        u64 init_bv = xfeatures_mask & ~xbv;
                        if (unlikely(init_bv))
-                               xrstor_state(&init_xstate_ctx, init_bv);
+                               xrstor_state(&init_fpstate.xsave, init_bv);
                        return xrestore_user(buf, xbv);
                }
        } else if (use_fxsr()) {
@@ -665,20 +660,20 @@ static void setup_init_fpu_buf(void)
        print_xstate_features();
 
        if (cpu_has_xsaves) {
-               init_xstate_ctx.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
-               init_xstate_ctx.header.xfeatures = xfeatures_mask;
+               init_fpstate.xsave.header.xcomp_bv = (u64)1 << 63 | xfeatures_mask;
+               init_fpstate.xsave.header.xfeatures = xfeatures_mask;
        }
 
        /*
         * Init all the features state with header_bv being 0x0
         */
-       xrstor_state_booting(&init_xstate_ctx, -1);
+       xrstor_state_booting(&init_fpstate.xsave, -1);
 
        /*
         * Dump the init state again. This is to identify the init state
         * of any feature which is not represented by all zero's.
         */
-       xsave_state_booting(&init_xstate_ctx);
+       xsave_state_booting(&init_fpstate.xsave);
 }
 
 /*