On Wed, 20 Feb 2008 13:07:47 +0100 Ingo Molnar <[EMAIL PROTECTED]> wrote:
> > * Mike Travis <[EMAIL PROTECTED]> wrote: > > > * Declare the pda as a per cpu variable. This will move the pda area > > to an address accessible by the x86_64 per cpu macros. > > Subtraction of __per_cpu_start will make the offset based from the > > beginning of the per cpu area. Since %gs is pointing to the pda, > > it will then also point to the per cpu variables and can be > > accessed thusly: > > > > %gs:[&per_cpu_xxxx - __per_cpu_start] > > randconfig QA on x86.git found a crash on x86.git#testing with > nmi_watchdog=2 (config attached) - and i bisected it down to this patch. > > config and crashlog attached. You can pick up x86.git#testing via: > > http://people.redhat.com/mingo/x86.git/README > > (since i had to hand-merge the patch when integrating it, i've attached > the merged version below.) > > Ingo > > --------------> > Subject: x86_64: Fold pda into per cpu area v3 > From: Mike Travis <[EMAIL PROTECTED]> > Date: Tue, 19 Feb 2008 12:33:36 -0800 > > * Declare the pda as a per cpu variable. This will move the pda area > to an address accessible by the x86_64 per cpu macros. Subtraction > of __per_cpu_start will make the offset based from the beginning > of the per cpu area. Since %gs is pointing to the pda, it will > then also point to the per cpu variables and can be accessed thusly: > > %gs:[&per_cpu_xxxx - __per_cpu_start] > > * The boot_pdas are only needed in head64.c so move the declaration > over there. And since the boot_cpu_pda is only used during > bootup and then copied to the per_cpu areas during init, it is > then removable. In addition, the initial cpu_pda pointer table > is reallocated to be the correct size for the number of cpus. > > * Remove the code that allocates special pda data structures. > Since the percpu area is currently maintained for all possible > cpus then the pda regions will stay intact in case cpus are > hotplugged off and then back on. > > * Relocate the x86_64 percpu variables to begin at zero. Then > we can directly use the x86_32 percpu operations. x86_32 > offsets %fs by __per_cpu_start. x86_64 has %gs pointing > directly to the pda and the per cpu area thereby allowing > access to the pda with the x86_64 pda operations and access > to the per cpu variables using x86_32 percpu operations. > > * This also supports further integration of x86_32/64. > > Cc: Andy Whitcroft <[EMAIL PROTECTED]> > Cc: Randy Dunlap <[EMAIL PROTECTED]> > Cc: Joel Schopp <[EMAIL PROTECTED]> > Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]> > Signed-off-by: Mike Travis <[EMAIL PROTECTED]> > Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]> > --- > arch/x86/Kconfig | 3 + > arch/x86/kernel/head64.c | 41 ++++++++++++++++++++++++ > arch/x86/kernel/setup64.c | 66 > ++++++++++++++++++++++++--------------- > arch/x86/kernel/smpboot_64.c | 16 --------- > arch/x86/kernel/vmlinux_64.lds.S | 1 > include/asm-x86/pda.h | 13 +++++-- > include/asm-x86/percpu.h | 33 +++++++++++-------- > 7 files changed, 115 insertions(+), 58 deletions(-) > > Index: linux-x86.q/arch/x86/Kconfig > =================================================================== > --- linux-x86.q.orig/arch/x86/Kconfig > +++ linux-x86.q/arch/x86/Kconfig > @@ -122,6 +122,9 @@ config ARCH_HAS_CPU_RELAX > config HAVE_SETUP_PER_CPU_AREA > def_bool X86_64 > > +config HAVE_ZERO_BASED_PER_CPU > + def_bool X86_64 > + > config ARCH_HIBERNATION_POSSIBLE > def_bool y > depends on !SMP || !X86_VOYAGER > Index: linux-x86.q/arch/x86/kernel/head64.c > =================================================================== > --- linux-x86.q.orig/arch/x86/kernel/head64.c > +++ linux-x86.q/arch/x86/kernel/head64.c > @@ -11,6 +11,7 @@ > #include <linux/string.h> > #include <linux/percpu.h> > #include <linux/start_kernel.h> > +#include <linux/bootmem.h> > > #include <asm/processor.h> > #include <asm/proto.h> > @@ -23,6 +24,12 @@ > #include <asm/kdebug.h> > #include <asm/e820.h> > > +#ifdef CONFIG_SMP > +/* Only used before the per cpu areas are setup. */ > +static struct x8664_pda boot_cpu_pda[NR_CPUS] __initdata; > +static struct x8664_pda *_cpu_pda_init[NR_CPUS] __initdata; > +#endif > + > static void __init zap_identity_mappings(void) > { > pgd_t *pgd = pgd_offset_k(0UL); > @@ -102,8 +109,14 @@ void __init x86_64_start_kernel(char * r > > early_printk("Kernel alive\n"); > > +#ifdef CONFIG_SMP > + _cpu_pda = (void *)_cpu_pda_init; > for (i = 0; i < NR_CPUS; i++) > cpu_pda(i) = &boot_cpu_pda[i]; > +#endif > + > + /* setup percpu segment offset for cpu 0 */ > + cpu_pda(0)->data_offset = (unsigned long)__per_cpu_load; > > pda_init(0); > copy_bootdata(__va(real_mode_data)); > @@ -128,3 +141,31 @@ void __init x86_64_start_kernel(char * r > > start_kernel(); > } > + > +#ifdef CONFIG_SMP > +/* > + * Remove initial boot_cpu_pda array and cpu_pda pointer table. > + * > + * This depends on setup_per_cpu_areas relocating the pda to the beginning > + * of the per_cpu area so that (_cpu_pda[i] != &boot_cpu_pda[i]). If it > + * is equal then the new pda has not been setup for this cpu, and the pda > + * table will have a NULL address for this cpu. > + */ > +void __init x86_64_cleanup_pda(void) > +{ > + int i; > + > + _cpu_pda = alloc_bootmem_low(nr_cpu_ids * sizeof(void *)); Here we allocate an array of [nr_cpu_ids] slots > + > + if (!_cpu_pda) > + panic("Cannot allocate cpu pda table\n"); > + > + /* cpu_pda() now points to allocated cpu_pda_table */ > + > + for (i = 0; i < NR_CPUS; i++) But in this loop we want to read/write on [NR_CPUS] slots of this array > + if (_cpu_pda_init[i] == &boot_cpu_pda[i]) > + cpu_pda(i) = NULL; > + else > + cpu_pda(i) = _cpu_pda_init[i]; > +} > +#endif You might want to apply this patch. I also wonder if _cpu_pda should be set only at the very end of x86_64_cleanup_pda(), after array initialization, or maybe other cpus are not yet running ? (Sorry I cannot boot test this patch at this momeent) [PATCH] x86_64: x86_64_cleanup_pda() should use nr_cpu_ids instead of NR_CPUS We allocate an array of nr_cpu_ids pointers, so we should respect its bonds. Delay change of _cpu_pda after array initialization. Also take into account that alloc_bootmem_low() : - calls panic() if not enough memory - already clears allocated memory Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 3942e6a..21532eb 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -154,18 +154,16 @@ void __init x86_64_start_kernel(char * real_mode_data) void __init x86_64_cleanup_pda(void) { int i; + struct x8664_pda **new_cpu_pda; - _cpu_pda = alloc_bootmem_low(nr_cpu_ids * sizeof(void *)); + new_cpu_pda = alloc_bootmem_low(nr_cpu_ids * sizeof(void *)); - if (!_cpu_pda) - panic("Cannot allocate cpu pda table\n"); + for (i = 0; i < nr_cpu_ids; i++) + if (_cpu_pda_init[i] != &boot_cpu_pda[i]) + new_cpu_pda[i] = _cpu_pda_init[i]; + mb(); + _cpu_pda = new_cpu_pda; /* cpu_pda() now points to allocated cpu_pda_table */ - - for (i = 0; i < NR_CPUS; i++) - if (_cpu_pda_init[i] == &boot_cpu_pda[i]) - cpu_pda(i) = NULL; - else - cpu_pda(i) = _cpu_pda_init[i]; } #endif -- 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/
