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linuxkm/x86_vector_register_glue.c: fix can_save_vector_registers_x86() to check wc_linuxkm_fpu_states before calling irq_fpu_usable(), needed for recursive call patterns. also, check TIF_NEED_FPU_LOAD only if it's defined.

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This commit is contained in:
Daniel Pouzzner
2025-04-14 13:33:54 -05:00
parent bbe956cc0c
commit 755fa1a701
1 changed files with 25 additions and 1 deletions
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26
linuxkm/x86_vector_register_glue.c
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@ -400,12 +400,34 @@ static inline void wc_linuxkm_fpu_state_release(
WARN_UNUSED_RESULT int can_save_vector_registers_x86(void)
{
/* First, check if we're already saved, per wc_linuxkm_fpu_states.
*
* On kernel >= 6.15, irq_fpu_usable() dumps a backtrace to the kernel log
* if called while already saved, so it's crucial to preempt that call by
* checking wc_linuxkm_fpu_states.
*/
struct wc_thread_fpu_count_ent *pstate = wc_linuxkm_fpu_state_assoc(0);
if ((pstate != NULL) && (pstate->fpu_state != 0U)) {
if (unlikely((pstate->fpu_state & WC_FPU_COUNT_MASK)
== WC_FPU_COUNT_MASK))
{
/* would overflow */
return 0;
} else {
return 1;
}
}
if (irq_fpu_usable())
return 1;
else if (in_nmi() || (hardirq_count() > 0) || (softirq_count() > 0))
return 0;
#ifdef TIF_NEED_FPU_LOAD
else if (test_thread_flag(TIF_NEED_FPU_LOAD))
return 1;
#endif
return 0;
}
@ -441,7 +463,7 @@ WARN_UNUSED_RESULT int save_vector_registers_x86(void)
}
if (irq_fpu_usable()
#if (LINUX_VERSION_CODE < KERNEL_VERSION(5, 17, 0))
#if (LINUX_VERSION_CODE < KERNEL_VERSION(5, 17, 0)) && defined(TIF_NEED_FPU_LOAD)
/* work around a kernel bug -- see linux commit 59f5ede3bc0f0.
* what we really want here is this_cpu_read(in_kernel_fpu), but
* in_kernel_fpu is an unexported static array.
@ -489,6 +511,7 @@ WARN_UNUSED_RESULT int save_vector_registers_x86(void)
wc_linuxkm_fpu_state_release(pstate);
#endif
return BAD_STATE_E;
#ifdef TIF_NEED_FPU_LOAD
} else if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
static int warned_fpu_forbidden = 0;
if (! warned_fpu_forbidden)
@ -498,6 +521,7 @@ WARN_UNUSED_RESULT int save_vector_registers_x86(void)
wc_linuxkm_fpu_state_release(pstate);
#endif
return BAD_STATE_E;
#endif
} else {
/* assume already safely in_kernel_fpu from caller, but recursively
* preempt_disable() to be extra-safe.