On Mon, May 14, 2018 at 12:07:30PM +0100, Dave Martin wrote:
> On Mon, May 14, 2018 at 10:46:32AM +0100, Mark Rutland wrote:
> > diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
> > index 5df857e32b48..4706f841e758 100644
> > --- a/arch/arm64/kernel/syscall.c
> > +++ b/arch/arm64/kernel/syscall.c
> > @@ -6,7 +6,9 @@
> > #include <linux/ptrace.h>
> >
> > #include <asm/daifflags.h>
> > +#include <asm/fpsimd.h>
> > #include <asm/thread_info.h>
> > +#include <asm/unistd.h>
> >
> > long do_ni_syscall(struct pt_regs *regs);
> >
> > @@ -41,8 +43,8 @@ static inline bool has_syscall_work(unsigned long flags)
> > int syscall_trace_enter(struct pt_regs *regs);
> > void syscall_trace_exit(struct pt_regs *regs);
> >
> > -asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
> > - syscall_fn_t syscall_table[])
> > +static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
> > + syscall_fn_t syscall_table[])
> > {
> > unsigned long flags = current_thread_info()->flags;
> >
> > @@ -79,3 +81,37 @@ asmlinkage void el0_svc_common(struct pt_regs *regs, int
> > scno, int sc_nr,
> > trace_exit:
> > syscall_trace_exit(regs);
> > }
> > +
> > +static inline void sve_user_reset(void)
>
> Static function with no caller...
Ugh, this was intended to be called below in el0_svc_handler().
> > +{
> > + if (!system_supports_sve())
> > + return;
> > +
> > + /*
> > + * task_fpsimd_load() won't be called to update CPACR_EL1 in
> > + * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
> > + * happens if a context switch or kernel_neon_begin() or context
> > + * modification (sigreturn, ptrace) intervenes.
> > + * So, ensure that CPACR_EL1 is already correct for the fast-path case.
> > + */
> > + if (test_and_clear_thread_flag(TIF_SVE))
> > + sve_user_disable();
>
> sve_user_disable() is already inline, and incorporates the if()
> internally via sysreg_clear_set().
>
> So, should this just be
>
> clear_thread_flag(TIF_SVE);
> sve_user_disable();
Sure. That does mean we'll unconditionally read cpacr_el1, but I assume
you're happy with that. I'll note the difference in the commit message.
> > +}
> > +
> > +extern syscall_fn_t sys_call_table[];
> > +
> > +asmlinkage void el0_svc_handler(struct pt_regs *regs)
> > +{
>
> if (system_supports_sve()) ?
>
> > + sve_user_disable();
>
> Or should this be replaced by a call to sve_user_reset()?
>
> I suspect the latter, since we do want to be clearing TIF_SVE here too.
Yes, this was mean to be sve_user_reset().
Thanks,
Mark.
