Commit 50f408d9 authored by Kan Liang's avatar Kan Liang Committed by Peter Zijlstra
Browse files

x86/fpu/xstate: Add helpers for LBR dynamic supervisor feature 



The perf subsystem will only need to save/restore the LBR state.
However, the existing helpers save all supported supervisor states to a
kernel buffer, which will be unnecessary. Two helpers are introduced to
only save/restore requested dynamic supervisor states. The supervisor
features in XFEATURE_MASK_SUPERVISOR_SUPPORTED and
XFEATURE_MASK_SUPERVISOR_UNSUPPORTED mask cannot be saved/restored using
these helpers.

The helpers will be used in the following patch.

Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Link: https://lkml.kernel.org/r/1593780569-62993-22-git-send-email-kan.liang@linux.intel.com
parent f0dccc9d

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

+3 −0
Original line number Diff line number Diff line
@@ -106,6 +106,9 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i 
int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf);

int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf);

void copy_supervisor_to_kernel(struct xregs_state *xsave);

void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask);

void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask);





/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */

int validate_user_xstate_header(const struct xstate_header *hdr);

arch/x86/kernel/fpu/xstate.c

+72 −0
Original line number Diff line number Diff line
@@ -1361,6 +1361,78 @@ void copy_supervisor_to_kernel(struct xregs_state *xstate) 
	}

}



/**

 * copy_dynamic_supervisor_to_kernel() - Save dynamic supervisor states to

 *                                       an xsave area

 * @xstate: A pointer to an xsave area

 * @mask: Represent the dynamic supervisor features saved into the xsave area

 *

 * Only the dynamic supervisor states sets in the mask are saved into the xsave

 * area (See the comment in XFEATURE_MASK_DYNAMIC for the details of dynamic

 * supervisor feature). Besides the dynamic supervisor states, the legacy

 * region and XSAVE header are also saved into the xsave area. The supervisor

 * features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and

 * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not saved.

 *

 * The xsave area must be 64-bytes aligned.

 */

void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask)

{

	u64 dynamic_mask = xfeatures_mask_dynamic() & mask;

	u32 lmask, hmask;

	int err;



	if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))

		return;



	if (WARN_ON_FPU(!dynamic_mask))

		return;



	lmask = dynamic_mask;

	hmask = dynamic_mask >> 32;



	XSTATE_OP(XSAVES, xstate, lmask, hmask, err);



	/* Should never fault when copying to a kernel buffer */

	WARN_ON_FPU(err);

}



/**

 * copy_kernel_to_dynamic_supervisor() - Restore dynamic supervisor states from

 *                                       an xsave area

 * @xstate: A pointer to an xsave area

 * @mask: Represent the dynamic supervisor features restored from the xsave area

 *

 * Only the dynamic supervisor states sets in the mask are restored from the

 * xsave area (See the comment in XFEATURE_MASK_DYNAMIC for the details of

 * dynamic supervisor feature). Besides the dynamic supervisor states, the

 * legacy region and XSAVE header are also restored from the xsave area. The

 * supervisor features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and

 * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not restored.

 *

 * The xsave area must be 64-bytes aligned.

 */

void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask)

{

	u64 dynamic_mask = xfeatures_mask_dynamic() & mask;

	u32 lmask, hmask;

	int err;



	if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES)))

		return;



	if (WARN_ON_FPU(!dynamic_mask))

		return;



	lmask = dynamic_mask;

	hmask = dynamic_mask >> 32;



	XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);



	/* Should never fault when copying from a kernel buffer */

	WARN_ON_FPU(err);

}



#ifdef CONFIG_PROC_PID_ARCH_STATUS

/*

 * Report the amount of time elapsed in millisecond since last AVX512

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