On Thu, 23 Oct 2014, Minfei Huang wrote: > From: Minfei Huang <[email protected]> > > It is a problem when configuring high memory off where the vmalloc > reserve area could end up overlapping the early_ioremap fixmap > area on i386. > > The ordering of the VMALLOC_RESERVE space is: > FIXADDR_TOP > fixed_addresses > FIXADDR_START > early_ioremap fixed addresses > FIXADDR_BOOT_START > Persistent kmap area > PKMAP_BASE > VMALLOC_END > Vmalloc area > VMALLOC_START > high_memory > > The available address we can use is lower than FIXADDR_BOOT_START. So > We will set the kmap boundary below the FIXADDR_BOOT_START, if configure > the high memory. > > If we configure the high memory, the vmalloc reserve area should end > up to PKMAP_BASE, otherwise should end up to FIXADDR_BOOT_START.
Which is not really a problem, because the FIXADDR_BOOT area is only used during boot for early_ioremap() and it's unused when ioremap() is functional. vmalloc becomes available after early boot so the FIXADDR_BOOT area is available for reuse. Though in the highmem case the PKMAP area is not overlapping the FIXADDR_BOOT area. So having the !highmem case use the same layout (minus the PKMAP area) makes sense. Acked-by: Thomas Gleixner <[email protected]> > Signed-off-by: Minfei Huang <[email protected]> > --- > arch/x86/include/asm/pgtable_32_types.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/pgtable_32_types.h > b/arch/x86/include/asm/pgtable_32_types.h > index ed5903b..2ac5fc8 100644 > --- a/arch/x86/include/asm/pgtable_32_types.h > +++ b/arch/x86/include/asm/pgtable_32_types.h > @@ -43,7 +43,7 @@ extern bool __vmalloc_start_set; /* set once high_memory is > set */ > #ifdef CONFIG_HIGHMEM > # define VMALLOC_END (PKMAP_BASE - 2 * PAGE_SIZE) > #else > -# define VMALLOC_END (FIXADDR_START - 2 * PAGE_SIZE) > +# define VMALLOC_END (FIXADDR_BOOT_START - 2 * PAGE_SIZE) > #endif > > #define MODULES_VADDR VMALLOC_START > -- > 1.8.3.1 -- 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/
