| Message ID | 20190514014412.25373-1-shawn@git.icu (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/2,PowerPC] Add simd.h implementation | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (8150a153c013aa2dd1ffae43370b89ac1347a7fb) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 49 lines checked |
On Mon, 2019-05-13 at 22:44 -0300, Shawn Landden wrote: > + > +/* > + * Were we in user mode when we were > + * interrupted? > + * > + * Doing kernel_altivec/vsx_begin/end() is ok if we are running > + * in an interrupt context from user mode - we'll just > + * save the FPU state as required. > + */ > +static bool interrupted_user_mode(void) > +{ > + struct pt_regs *regs = get_irq_regs(); > + > + return regs && user_mode(regs); > +} > + That's interesting .... it *could* work but we'll have to careful audit the code to make sure thats ok. We probably also want to handle the case where the CPU is in the idle loop. Do we always save the user state when switching out these days ? If yes, then there's no "live" state to worry about... Cheers, Ben.
On Tue, May 14, 2019 at 12:43 AM Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote: > > On Mon, 2019-05-13 at 22:44 -0300, Shawn Landden wrote: > > + > > +/* > > + * Were we in user mode when we were > > + * interrupted? > > + * > > + * Doing kernel_altivec/vsx_begin/end() is ok if we are running > > + * in an interrupt context from user mode - we'll just > > + * save the FPU state as required. > > + */ > > +static bool interrupted_user_mode(void) > > +{ > > + struct pt_regs *regs = get_irq_regs(); > > + > > + return regs && user_mode(regs); > > +} > > + > > That's interesting .... it *could* work but we'll have to careful audit > the code to make sure thats ok. > > We probably also want to handle the case where the CPU is in the idle > loop. That is the next patch. It is best to split these up because then git bisect works better, and these are higher-risk changes. > > Do we always save the user state when switching out these days ? If > yes, then there's no "live" state to worry about... > > Cheers, > Ben. > >
diff --git a/arch/powerpc/include/asm/simd.h b/arch/powerpc/include/asm/simd.h new file mode 100644 index 000000000..2c02ad531 --- /dev/null +++ b/arch/powerpc/include/asm/simd.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ + +/* + * may_use_simd - whether it is allowable at this time to issue SIMD + * instructions or access the SIMD register file + * + * It's always ok in process context (ie "not interrupt") + * but it is sometimes ok even from an irq. + */ +static __must_check inline bool may_use_simd(void) +{ + return irq_simd_usable(); +} diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index dd9e0d538..e436d708a 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -345,6 +345,36 @@ static int restore_altivec(struct task_struct *tsk) } return 0; } + +/* + * Were we in user mode when we were + * interrupted? + * + * Doing kernel_altivec/vsx_begin/end() is ok if we are running + * in an interrupt context from user mode - we'll just + * save the FPU state as required. + */ +static bool interrupted_user_mode(void) +{ + struct pt_regs *regs = get_irq_regs(); + + return regs && user_mode(regs); +} + +/* + * Can we use SIMD in kernel mode with the + * whole "kernel_altivec/vsx_begin/end()" sequence? + * + * It's always ok in process context (ie "not interrupt") + * but it is sometimes ok even from an irq. + */ +bool irq_simd_usable(void) +{ + return !in_interrupt() || + interrupted_user_mode(); +} +EXPORT_SYMBOL(irq_simd_usable); + #else #define loadvec(thr) 0 static inline int restore_altivec(struct task_struct *tsk) { return 0; }
Based off the x86 one. WireGuard really wants to be able to do SIMD in interrupts, so it can accelerate its in-bound path. Signed-off-by: Shawn Landden <shawn@git.icu> --- arch/powerpc/include/asm/simd.h | 13 +++++++++++++ arch/powerpc/kernel/process.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+) create mode 100644 arch/powerpc/include/asm/simd.h