Not just crazy, but wrong - this *can* happen on pre-Montecito. Even though
L1D is write-through and L2 was mixed I/D, the L1 I-cache could contain
stale instrutions if there are missing flushes. I think the only reason this
has never been observed is that the L1I is so small (32K) that it's likely
that any stale data has been displaced.
-- Jim
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of
> KAMEZAWA Hiroyuki
> Sent: Monday, July 30, 2007 9:30 PM
> To: David Mosberger-Tang
> Cc: LKML; [email protected]; [email protected];
> [email protected]; Christoph Lameter
> Subject: Re: [PATCH] flush icache before set_pte take6. [4/4]
> optimization for cpus other than montecito
>
> On Mon, 30 Jul 2007 22:15:50 -0600
> "David Mosberger-Tang" <[email protected]> wrote:
>
> > This seems crazy to me. Flushing should occur according to the
> > *architecture*, not model-by-model. Even if we happen to
> get "lucky"
> > on pre-Montecito CPUs, that doesn't justify such ugly hacks.
>
> I'm not sure this can happen before Montecito because L1 was
> write-through
> and L2 was mixed.
>
> > Or you really want to debug this *again* come next CPU?
>
> No.
> I should add RFC to this patch. I just want to hear opinions.
> This is why I separated this patch. I can drop this.
>
> Thanks,
> -Kame
>
>
>
>
>
>
> > --david
> >
> > On 7/30/07, KAMEZAWA Hiroyuki
> <[email protected]> wrote:
> > >
> > > Add "L2 cache is separated? check flag" as read_mostly
> global variable.
> > >
> > > This add one memory reference to global variable to page
> faults of "executable"
> > > map in do_wp_page(page copy case), file-mapped page fault
> and some system calls
> > > which does memory map changes. But not so bad as calling
> sync_icache_dcache in
> > > architectures which doesn't need it.
> > >
> > > Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
> > >
> > >
> > > ---
> > > arch/ia64/kernel/setup.c | 7 +++++++
> > > include/asm-ia64/pgtable.h | 3 ++-
> > > 2 files changed, 9 insertions(+), 1 deletion(-)
> > >
> > > Index: linux-2.6.23-rc1.test/arch/ia64/kernel/setup.c
> > >
> ===================================================================
> > > --- linux-2.6.23-rc1.test.orig/arch/ia64/kernel/setup.c
> > > +++ linux-2.6.23-rc1.test/arch/ia64/kernel/setup.c
> > > @@ -106,6 +106,8 @@ struct io_space io_space[MAX_IO_SPACES];
> > > EXPORT_SYMBOL(io_space);
> > > unsigned int num_io_spaces;
> > >
> > > +int separated_l2_icache_dcache __read_mostly;
> > > +
> > > /*
> > > * "flush_icache_range()" needs to know what processor
> dependent stride size to use
> > > * when it makes i-cache(s) coherent with d-caches.
> > > @@ -718,6 +720,11 @@ get_model_name(__u8 family, __u8 model)
> > > printk(KERN_ERR
> > > "%s: Table overflow. Some
> processor model information will be missing\n",
> > > __FUNCTION__);
> > > + /* Montecito has separated L2 Icache and Dcache.
> This requires
> > > + synchronize Icache and Dcache before set_pte() */
> > > + if (family == 0x20)
> > > + separated_l2_icache_dcache = 1;
> > > +
> > > return "Unknown";
> > > }
> > >
> > > Index: linux-2.6.23-rc1.test/include/asm-ia64/pgtable.h
> > >
> ===================================================================
> > > --- linux-2.6.23-rc1.test.orig/include/asm-ia64/pgtable.h
> > > +++ linux-2.6.23-rc1.test/include/asm-ia64/pgtable.h
> > > @@ -489,9 +489,10 @@ extern struct page *zero_page_memmap_ptr
> > > * as an executable pte.
> > > */
> > > extern void __sync_icache_dcache(pte_t pte);
> > > +extern int separated_l2_icache_dcache;
> > > static inline void sync_icache_dcache(pte_t pte)
> > > {
> > > - if (pte_exec(pte))
> > > + if (pte_exec(pte) && separated_l2_icache_dcache)
> > > __sync_icache_dcache(pte);
> > > }
> > > #define __HAVE_ARCH_SYNC_ICACHE_DCACHE
> > >
> > > -
> > > To unsubscribe from this list: send the line "unsubscribe
> linux-ia64" in
> > > the body of a message to [email protected]
> > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > >
> >
> >
> > --
> > Mosberger Consulting LLC, http://www.mosberger-consulting.com/
> >
>
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-ia64" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
