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The IA32_XFD_MSR allows to arm #NM traps for XSTATE components which are enabled in XCR0. The register has to be restored before the tasks XSTATE is restored. The life time rules are the same as for FPU state. XFD is updated on return to userspace only when the FPU state of the task is not up to date in the registers. It's updated before the XRSTORS so that eventually enabled dynamic features are restored as well and not brought into init state. Also in signal handling for restoring FPU state from user space the correctness of the XFD state has to be ensured. Add it to CPU initialization and resume as well. Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lore.kernel.org/r/20211021225527.10184-17-chang.seok.bae@intel.com
84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __X86_KERNEL_FPU_CONTEXT_H
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#define __X86_KERNEL_FPU_CONTEXT_H
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#include <asm/fpu/xstate.h>
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#include <asm/trace/fpu.h>
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/* Functions related to FPU context tracking */
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/*
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* The in-register FPU state for an FPU context on a CPU is assumed to be
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* valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
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* matches the FPU.
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*
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* If the FPU register state is valid, the kernel can skip restoring the
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* FPU state from memory.
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*
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* Any code that clobbers the FPU registers or updates the in-memory
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* FPU state for a task MUST let the rest of the kernel know that the
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* FPU registers are no longer valid for this task.
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*
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* Either one of these invalidation functions is enough. Invalidate
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* a resource you control: CPU if using the CPU for something else
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* (with preemption disabled), FPU for the current task, or a task that
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* is prevented from running by the current task.
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*/
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static inline void __cpu_invalidate_fpregs_state(void)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
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}
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static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
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{
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fpu->last_cpu = -1;
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}
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static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
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{
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return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
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}
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static inline void fpregs_deactivate(struct fpu *fpu)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
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trace_x86_fpu_regs_deactivated(fpu);
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}
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static inline void fpregs_activate(struct fpu *fpu)
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{
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__this_cpu_write(fpu_fpregs_owner_ctx, fpu);
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trace_x86_fpu_regs_activated(fpu);
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}
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/* Internal helper for switch_fpu_return() and signal frame setup */
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static inline void fpregs_restore_userregs(void)
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{
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struct fpu *fpu = ¤t->thread.fpu;
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int cpu = smp_processor_id();
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if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
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return;
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if (!fpregs_state_valid(fpu, cpu)) {
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/*
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* This restores _all_ xstate which has not been
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* established yet.
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*
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* If PKRU is enabled, then the PKRU value is already
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* correct because it was either set in switch_to() or in
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* flush_thread(). So it is excluded because it might be
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* not up to date in current->thread.fpu.xsave state.
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*
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* XFD state is handled in restore_fpregs_from_fpstate().
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*/
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restore_fpregs_from_fpstate(fpu->fpstate, XFEATURE_MASK_FPSTATE);
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fpregs_activate(fpu);
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fpu->last_cpu = cpu;
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}
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clear_thread_flag(TIF_NEED_FPU_LOAD);
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}
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#endif
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