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Commit 1499ce2d authored by Yu-cheng Yu's avatar Yu-cheng Yu Committed by Ingo Molnar
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x86/fpu/xstate: Fix supervisor xstate component offset 



CPUID function 0x0d, sub function (i, i > 1) returns in ebx the offset of
xstate component i. Zero is returned for a supervisor state. A supervisor
state can only be saved by XSAVES and XSAVES uses a compacted format.
There is no fixed offset for a supervisor state. This patch checks and
makes sure a supervisor state offset is not recorded or mis-used. This has
no effect in practice as we currently use no supervisor states, but it
would be good to fix.

Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/81b29e40d35d4cec9f2511a856fe769f34935a3f.1466179491.git.yu-cheng.yu@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 03482e08

arch/x86/include/asm/fpu/types.h

+1 −0
Original line number Diff line number Diff line
@@ -122,6 +122,7 @@ enum xfeature { 
#define XFEATURE_MASK_OPMASK		(1 << XFEATURE_OPMASK)

#define XFEATURE_MASK_ZMM_Hi256		(1 << XFEATURE_ZMM_Hi256)

#define XFEATURE_MASK_Hi16_ZMM		(1 << XFEATURE_Hi16_ZMM)

#define XFEATURE_MASK_PT		(1 << XFEATURE_PT_UNIMPLEMENTED_SO_FAR)

#define XFEATURE_MASK_PKRU		(1 << XFEATURE_PKRU)



#define XFEATURE_MASK_FPSSE		(XFEATURE_MASK_FP | XFEATURE_MASK_SSE)

arch/x86/include/asm/fpu/xstate.h

+3 −0
Original line number Diff line number Diff line
@@ -18,6 +18,9 @@ 
#define XSAVE_YMM_SIZE	    256

#define XSAVE_YMM_OFFSET    (XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET)



/* Supervisor features */

#define XFEATURE_MASK_SUPERVISOR (XFEATURE_MASK_PT)



/* Supported features which support lazy state saving */

#define XFEATURE_MASK_LAZY	(XFEATURE_MASK_FP | \

				 XFEATURE_MASK_SSE | \

arch/x86/kernel/fpu/xstate.c

+39 −23
Original line number Diff line number Diff line
@@ -112,6 +112,27 @@ int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) 
}

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.

	 */

	u32 eax, ebx, ecx, edx;



	cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);

	return !!(ecx & 1);

}



static int xfeature_is_user(int xfeature_nr)

{

	return !xfeature_is_supervisor(xfeature_nr);

}



/*

 * When executing XSAVEOPT (or other optimized XSAVE instructions), if

 * a processor implementation detects that an FPU state component is still
@@ -230,7 +251,14 @@ static void __init setup_xstate_features(void) 
			continue;



		cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);



		/*

		 * If an xfeature is supervisor state, the offset

		 * in EBX is invalid. We leave it to -1.

		 */

		if (xfeature_is_user(i))

			xstate_offsets[i] = ebx;



		xstate_sizes[i] = eax;

		/*

		 * In our xstate size checks, we assume that the
@@ -375,31 +403,19 @@ static void __init setup_init_fpu_buf(void) 
	copy_xregs_to_kernel_booting(&init_fpstate.xsave);

}



static int xfeature_is_supervisor(int xfeature_nr)

static int xfeature_uncompacted_offset(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.

	u32 eax, ebx, ecx, edx;

	cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx;

	return !!(ecx & 1);

	*/

	return 0;

}



	/*

static int xfeature_is_user(int xfeature_nr)

{

	return !xfeature_is_supervisor(xfeature_nr);

}

	 * Only XSAVES supports supervisor states and it uses compacted

	 * format. Checking a supervisor state's uncompacted offset is

	 * an error.

	 */



static int xfeature_uncompacted_offset(int xfeature_nr)

{

	u32 eax, ebx, ecx, edx;

	if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) {

		WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);

		return -1;

	}



	CHECK_XFEATURE(xfeature_nr);

	cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);