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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2019-04-03 19:41:45 +0300 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2019-04-11 17:21:51 +0300 |
| commit | 383c252545edcc708128e2028a2318b05c45ede4 (patch) | |
| tree | 87b10ca634f95d0d875d7f0af65d39808897efb5 /arch/x86/include/asm/fpu | |
| parent | 0cecca9d03c964abbd2b7927d0670eb70db4ebf2 (diff) | |
| download | linux-383c252545edcc708128e2028a2318b05c45ede4.tar.xz | |
x86/entry: Add TIF_NEED_FPU_LOAD
Add TIF_NEED_FPU_LOAD. This flag is used for loading the FPU registers
before returning to userland. It must not be set on systems without a
FPU.
If this flag is cleared, the CPU's FPU registers hold the latest,
up-to-date content of the current task's (current()) FPU registers.
The in-memory copy (union fpregs_state) is not valid.
If this flag is set, then all of CPU's FPU registers may hold a random
value (except for PKRU) and it is required to load the content of the
FPU registers on return to userland.
Introduce it now as a preparatory change before adding the main feature.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-17-bigeasy@linutronix.de
Diffstat (limited to 'arch/x86/include/asm/fpu')
| -rw-r--r-- | arch/x86/include/asm/fpu/internal.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 6eb4a0b1ad0e..da75d7b3e37d 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -508,6 +508,14 @@ static inline void __fpregs_load_activate(struct fpu *fpu, int cpu) * - switch_fpu_finish() restores the new state as * necessary. * + * If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers + * are saved in the current thread's FPU register state. + * + * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not + * hold current()'s FPU registers. It is required to load the + * registers before returning to userland or using the content + * otherwise. + * * The FPU context is only stored/restored for a user task and * ->mm is used to distinguish between kernel and user threads. */ |