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| author | Chang S. Bae <chang.seok.bae@intel.com> | 2021-10-21 15:55:22 -0700 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2021-10-26 10:53:02 +0200 |
| commit | 500afbf645a040a39e1af0dba2fdf6ebf224bd47 (patch) | |
| tree | 31a57a92d06da8df3b4198090d1d1440d37c7184 /arch/x86/kernel/process.c | |
| parent | 783e87b404956f8958657aed8a6a72aa98d5b7e1 (diff) | |
| download | lwn-500afbf645a040a39e1af0dba2fdf6ebf224bd47.tar.gz lwn-500afbf645a040a39e1af0dba2fdf6ebf224bd47.zip | |
x86/fpu/xstate: Add fpstate_realloc()/free()
The fpstate embedded in struct fpu is the default state for storing the FPU
registers. It's sized so that the default supported features can be stored.
For dynamically enabled features the register buffer is too small.
The #NM handler detects first use of a feature which is disabled in the
XFD MSR. After handling permission checks it recalculates the size for
kernel space and user space state and invokes fpstate_realloc() which
tries to reallocate fpstate and install it.
Provide the allocator function which checks whether the current buffer size
is sufficient and if not allocates one. If allocation is successful the new
fpstate is initialized with the new features and sizes and the now enabled
features is removed from the task's XFD mask.
realloc_fpstate() uses vzalloc(). If use of this mechanism grows to
re-allocate buffers larger than 64KB, a more sophisticated allocation
scheme that includes purpose-built reclaim capability might be justified.
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/20211021225527.10184-19-chang.seok.bae@intel.com
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 99025e32f105..f3f251787b99 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -32,6 +32,7 @@ #include <asm/mwait.h> #include <asm/fpu/api.h> #include <asm/fpu/sched.h> +#include <asm/fpu/xstate.h> #include <asm/debugreg.h> #include <asm/nmi.h> #include <asm/tlbflush.h> @@ -90,9 +91,18 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) #endif /* Drop the copied pointer to current's fpstate */ dst->thread.fpu.fpstate = NULL; + return 0; } +#ifdef CONFIG_X86_64 +void arch_release_task_struct(struct task_struct *tsk) +{ + if (fpu_state_size_dynamic()) + fpstate_free(&tsk->thread.fpu); +} +#endif + /* * Free thread data structures etc.. */ |