| Message ID | 1499898783-25732-3-git-send-email-mark.rutland@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: alternative VMAP_STACK implementation | expand |
Hi Mark, On 12/07/17 23:32, Mark Rutland wrote: > Currently we define THREAD_SIZE_ORDER dependent on which arm64-specific > page size kconfig symbol was selected. This is unfortunate, as it hides > the relationship between THREAD_SIZE_ORDER and THREAD_SIZE, and makes it > painful more painful than necessary to modify the thread size as we will > need to do for some debug configurations. > > This patch follows arch/metag's approach of consistently defining > THREAD_SIZE in terms of THREAD_SIZE_ORDER. This avoids having ifdefs for > particular page size configurations, and allows us to change a single > definition to change the thread size. I think this has unintended side effects for 64K page systems. (or at least not yet intended) Today: > #ifdef CONFIG_ARM64_4K_PAGES > #define THREAD_SIZE_ORDER 2 > #elif defined(CONFIG_ARM64_16K_PAGES) > #define THREAD_SIZE_ORDER 0 > #endif Means THREAD_SIZE_ORDER is unset on 64K, and THREAD_SIZE is always: > #define THREAD_SIZE 16384 /kernel/fork.c matches this with its: > # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) [...] > #else [...] > void thread_stack_cache_init(void) > { > thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, > THREAD_SIZE, 0, NULL); > BUG_ON(thread_stack_cache == NULL); > } > #endif To create a kmemcache to share 64K pages as 16K stacks. After this patch: > #define THREAD_SHIFT 14 > > #if THREAD_SHIFT >= PAGE_SHIFT > #define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) > #else > #define THREAD_SIZE_ORDER 0 > #endif Means THREAD_SIZE_ORDER is 0, and: > #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) gives us a 64K THREAD_SIZE. Thanks, James > diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > index 141f13e9..6d0c59a 100644 > --- a/arch/arm64/include/asm/thread_info.h > +++ b/arch/arm64/include/asm/thread_info.h > @@ -23,13 +23,17 @@ > > #include <linux/compiler.h> > > -#ifdef CONFIG_ARM64_4K_PAGES > -#define THREAD_SIZE_ORDER 2 > -#elif defined(CONFIG_ARM64_16K_PAGES) > +#include <asm/page.h> > + > +#define THREAD_SHIFT 14 > + > +#if THREAD_SHIFT >= PAGE_SHIFT > +#define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) > +#else > #define THREAD_SIZE_ORDER 0 > #endif > > -#define THREAD_SIZE 16384 > +#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) > #define THREAD_START_SP (THREAD_SIZE - 16) > > #ifndef __ASSEMBLY__ >
On Thu, Jul 13, 2017 at 11:18:35AM +0100, James Morse wrote: > Hi Mark, > > On 12/07/17 23:32, Mark Rutland wrote: > > Currently we define THREAD_SIZE_ORDER dependent on which arm64-specific > > page size kconfig symbol was selected. This is unfortunate, as it hides > > the relationship between THREAD_SIZE_ORDER and THREAD_SIZE, and makes it > > painful more painful than necessary to modify the thread size as we will > > need to do for some debug configurations. > > > > This patch follows arch/metag's approach of consistently defining > > THREAD_SIZE in terms of THREAD_SIZE_ORDER. This avoids having ifdefs for > > particular page size configurations, and allows us to change a single > > definition to change the thread size. > > I think this has unintended side effects for 64K page systems. (or at least not > yet intended) > > Today: > > #ifdef CONFIG_ARM64_4K_PAGES > > #define THREAD_SIZE_ORDER 2 > > #elif defined(CONFIG_ARM64_16K_PAGES) > > #define THREAD_SIZE_ORDER 0 > > #endif > > Means THREAD_SIZE_ORDER is unset on 64K, and THREAD_SIZE is always: > > #define THREAD_SIZE 16384 > > /kernel/fork.c matches this with its: > > # if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) > [...] > > #else > [...] > > void thread_stack_cache_init(void) > > { > > thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE, > > THREAD_SIZE, 0, NULL); > > BUG_ON(thread_stack_cache == NULL); > > } > > #endif > > To create a kmemcache to share 64K pages as 16K stacks. > > > After this patch: > > #define THREAD_SHIFT 14 > > > > #if THREAD_SHIFT >= PAGE_SHIFT > > #define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) > > #else > > #define THREAD_SIZE_ORDER 0 > > #endif > > Means THREAD_SIZE_ORDER is 0, and: > > #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) > > gives us a 64K THREAD_SIZE. Yes; I'd gotten confused as to what I was doing here. Thanks for spotting that. I've folded this and the next patch, with the resultant logic being as below, which I think fixes this. Thanks, Mark. ---->8---- #define MIN_THREAD_SHIFT 14 /* * Each VMAP stack is a separate VMALLOC allocation, which is at least * PAGE_SIZE. */ #if defined(CONFIG_VMAP_STACK) && (MIN_THREAD_SHIFT < PAGE_SHIFT) #define THREAD_SHIFT PAGE_SHIFT #else #define THREAD_SHIFT MIN_THREAD_SHIFT #endif #if THREAD_SHIFT >= PAGE_SHIFT #define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) #endif #define THREAD_SIZE (1UL << THREAD_SHIFT) #define THREAD_START_SP (THREAD_SIZE - 16)
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 141f13e9..6d0c59a 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -23,13 +23,17 @@ #include <linux/compiler.h> -#ifdef CONFIG_ARM64_4K_PAGES -#define THREAD_SIZE_ORDER 2 -#elif defined(CONFIG_ARM64_16K_PAGES) +#include <asm/page.h> + +#define THREAD_SHIFT 14 + +#if THREAD_SHIFT >= PAGE_SHIFT +#define THREAD_SIZE_ORDER (THREAD_SHIFT - PAGE_SHIFT) +#else #define THREAD_SIZE_ORDER 0 #endif -#define THREAD_SIZE 16384 +#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) #define THREAD_START_SP (THREAD_SIZE - 16) #ifndef __ASSEMBLY__
Currently we define THREAD_SIZE_ORDER dependent on which arm64-specific page size kconfig symbol was selected. This is unfortunate, as it hides the relationship between THREAD_SIZE_ORDER and THREAD_SIZE, and makes it painful more painful than necessary to modify the thread size as we will need to do for some debug configurations. This patch follows arch/metag's approach of consistently defining THREAD_SIZE in terms of THREAD_SIZE_ORDER. This avoids having ifdefs for particular page size configurations, and allows us to change a single definition to change the thread size. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/include/asm/thread_info.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) -- 1.9.1