Messages in this thread Patch in this message | | | Date | Wed, 30 May 2007 13:33:59 -0700 | From | Andrew Morton <> | Subject | Re: [patch 8/9] F00F bug fixup for i386 - use conditional calls |
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On Wed, 30 May 2007 10:00:33 -0400 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> Use the faster conditional calls for F00F bug handling in do_page_fault. >
I guess this means that CONDCALL will be enabled on pretty much all i386, in which case making the whole feature Kconfigurable is starting to look marginal.
Perhaps a better approach would have to made this change dependent upon CONDCALL, rather than forcing it on.
> @@ -1084,6 +1085,7 @@ > */ > idt_descr.address = fix_to_virt(FIX_F00F_IDT); > load_idt(&idt_descr); > + BUG_ON(cond_call_arm("fix_f00f"));
It is generally poor C style to do
assert(something_which_has_side_effects())
because people can legitimately expect to do
#define assert() /*nothing*/
for production code.
The kernel doesn't actually do the right thing here when CONFIG_BUG=n, sadly. But still, children might be watching, so the better and preferred style is
if (cond_call_arm("fix_f00f")) BUG();
> } > #endif > > Index: linux-2.6-lttng/arch/i386/mm/fault.c > =================================================================== > --- linux-2.6-lttng.orig/arch/i386/mm/fault.c 2007-05-29 11:05:48.000000000 -0400 > +++ linux-2.6-lttng/arch/i386/mm/fault.c 2007-05-29 11:13:16.000000000 -0400 > @@ -25,6 +25,7 @@ > #include <linux/kprobes.h> > #include <linux/uaccess.h> > #include <linux/kdebug.h> > +#include <linux/condcall.h> > > #include <asm/system.h> > #include <asm/desc.h> > @@ -221,6 +222,25 @@ > > fastcall void do_invalid_op(struct pt_regs *, unsigned long); > > +#ifdef CONFIG_X86_F00F_BUG > +/* > + * Pentium F0 0F C7 C8 bug workaround. > + */ > +static inline int do_f00f_workaround(struct pt_regs *regs, > + unsigned long address) > +{ > + unsigned long nr; > + > + nr = (address - idt_descr.address) >> 3; > + > + if (nr == 6) { > + do_invalid_op(regs, 0); > + return 1; > + } > + return 0; > +} > +#endif > + > static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) > { > unsigned index = pgd_index(address); > @@ -474,19 +494,8 @@ > } > > #ifdef CONFIG_X86_F00F_BUG > - /* > - * Pentium F0 0F C7 C8 bug workaround. > - */ > - if (boot_cpu_data.f00f_bug) { > - unsigned long nr; > - > - nr = (address - idt_descr.address) >> 3; > - > - if (nr == 6) { > - do_invalid_op(regs, 0); > - return; > - } > - } > + if (cond_call(fix_f00f, do_f00f_workaround(regs, address))) > + return;
We do a cond_call() to an inlined function? That's a bit weird, isn't it?
> #endif > > no_context: > Index: linux-2.6-lttng/arch/i386/Kconfig.cpu > =================================================================== > --- linux-2.6-lttng.orig/arch/i386/Kconfig.cpu 2007-05-29 11:51:46.000000000 -0400 > +++ linux-2.6-lttng/arch/i386/Kconfig.cpu 2007-05-29 11:52:08.000000000 -0400 > @@ -275,6 +275,7 @@ > config X86_F00F_BUG > bool > depends on M586MMX || M586TSC || M586 || M486 || M386 > + select COND_CALL
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