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

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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: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Link: https://lkml.kernel.org/r/1593780569-62993-22-git-send-email-kan.liang@linux.intel.com
This commit is contained in:
Kan Liang 2020-07-03 05:49:27 -07:00 committed by Peter Zijlstra
parent f0dccc9da4
commit 50f408d96d
2 changed files with 75 additions and 0 deletions
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3
arch/x86/include/asm/fpu/xstate.h
View File

@ -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);

72
arch/x86/kernel/fpu/xstate.c
View File

@ -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