| Message ID | 1410546745-919-1-git-send-email-tony@atomide.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Sep 12, 2014 at 11:32 AM, Tony Lindgren <tony@atomide.com> wrote: > From: Rob Herring <robherring2@gmail.com> > > Currently trying to use pstore on at least ARMs can hang as we're > mapping the peristent RAM with pgprot_noncached(). > > On ARMs, pgprot_noncached() will actually make the memory strongly > ordered, and as the atomic operations pstore uses are implementation > defined for strongly ordered memory, they may not work. So basically > atomic operations have undefined behavior on ARM for device or strongly > ordered memory types. > > Let's fix the issue by using write-combine variants for mappings. This > corresponds to normal, non-cacheable memory on ARM. For many other > architectures, this change does not change the mapping type as by > default we have: > > #define pgprot_writecombine pgprot_noncached > > The reason why pgprot_noncached() was originaly used for pstore > is because Colin Cross <ccross@android.com> had observed lost > debug prints right before a device hanging write operation on some > systems. For the platforms supporting pgprot_noncached(), we can > add a an optional configuration option to support that. But let's > get pstore working first before adding new features. > > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Anton Vorontsov <cbouatmailru@gmail.com> > Cc: Colin Cross <ccross@android.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Olof Johansson <olof@lixom.net> > Cc: Tony Luck <tony.luck@intel.com> > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Rob Herring <rob.herring@calxeda.com> > [tony@atomide.com: updated description] > Signed-off-by: Tony Lindgren <tony@atomide.com> Acked-by: Kees Cook <keescook@chromium.org> Please Cc: stable@vger.kernel.org on this one too. Thanks! -Kees > --- > fs/pstore/ram_core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c > index 9d7b9a8..24f94b0 100644 > --- a/fs/pstore/ram_core.c > +++ b/fs/pstore/ram_core.c > @@ -392,7 +392,7 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size) > page_start = start - offset_in_page(start); > page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE); > > - prot = pgprot_noncached(PAGE_KERNEL); > + prot = pgprot_writecombine(PAGE_KERNEL); > > pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL); > if (!pages) { > @@ -422,7 +422,7 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size) > buffer_start_add = buffer_start_add_locked; > buffer_size_add = buffer_size_add_locked; > > - return ioremap(start, size); > + return ioremap_wc(start, size); > } > > static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size, > -- > 2.1.0 >
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 9d7b9a8..24f94b0 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -392,7 +392,7 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size) page_start = start - offset_in_page(start); page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE); - prot = pgprot_noncached(PAGE_KERNEL); + prot = pgprot_writecombine(PAGE_KERNEL); pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL); if (!pages) { @@ -422,7 +422,7 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size) buffer_start_add = buffer_start_add_locked; buffer_size_add = buffer_size_add_locked; - return ioremap(start, size); + return ioremap_wc(start, size); } static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size,