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* [PATCH V3] MIPS: make userspace mapping young by default
@ 2020-09-19  7:47 Huang Pei
  2020-09-28  6:39 ` Huang Pei
  2020-10-02 12:35 ` Thomas Bogendoerfer
  0 siblings, 2 replies; 4+ messages in thread
From: Huang Pei @ 2020-09-19  7:47 UTC (permalink / raw)
  To: Thomas Bogendoerfer, ambrosehua
  Cc: Bibo Mao, Andrew Morton, linux-mips, linux-arch, linux-mm,
	Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu, Gao Juxin,
	Fuxin Zhang, Huacai Chen

MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
the second TLB Invalid exception is just triggered by __update_tlb from
do_page_fault writing tlb without _PAGE_VALID set. With this patch, it
only take 1 TLB Miss + 1 TLB Invalid exceptions

This version removes pte_sw_mkyoung without polluting MM code and makes
page fault delay of MIPS on par with other architecture and covers both
no-RIXI and RIXI MIPS CPUS

[1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
-maobibo@loongson.cn/
---
V3:
- reformat with whitespace cleaned up following Thomas's advice
V2:
- remove unused asm-generic definition of pte_sw_mkyoung following Mao's
advice
---
Co-developed-by: Huang Pei <huangpei@loongson.cn>
Signed-off-by: Huang Pei <huangpei@loongson.cn>
Co-developed-by: Bibo Mao <maobibo@loonson.cn>
---
 arch/mips/include/asm/pgtable.h | 10 ++++------
 arch/mips/mm/cache.c            | 25 +++++++++++++------------
 include/linux/pgtable.h         |  8 --------
 mm/memory.c                     |  3 ---
 4 files changed, 17 insertions(+), 29 deletions(-)

diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index dd7a0f552cac..931fb35730f0 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -27,11 +27,11 @@ struct vm_area_struct;
 
 #define PAGE_NONE	__pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
 				 _page_cachable_default)
-#define PAGE_SHARED	__pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
-				 _page_cachable_default)
+#define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
+				 __READABLE | _page_cachable_default)
 #define PAGE_COPY	__pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
-				 _page_cachable_default)
-#define PAGE_READONLY	__pgprot(_PAGE_PRESENT | \
+				 __READABLE | _page_cachable_default)
+#define PAGE_READONLY	__pgprot(_PAGE_PRESENT |  __READABLE | \
 				 _page_cachable_default)
 #define PAGE_KERNEL	__pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
 				 _PAGE_GLOBAL | _page_cachable_default)
@@ -414,8 +414,6 @@ static inline pte_t pte_mkyoung(pte_t pte)
 	return pte;
 }
 
-#define pte_sw_mkyoung	pte_mkyoung
-
 #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
 static inline int pte_huge(pte_t pte)	{ return pte_val(pte) & _PAGE_HUGE; }
 
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 3e81ba000096..ed75f2871aad 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -159,22 +159,23 @@ static inline void setup_protection_map(void)
 {
 	if (cpu_has_rixi) {
 		protection_map[0]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
-		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
+		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
 		protection_map[2]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
-		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
-		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
-		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
-		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
-		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
+		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
+		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
+		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
+		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
+		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
 
 		protection_map[8]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
-		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
+		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
 		protection_map[10] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | _PAGE_NO_READ);
-		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
-		protection_map[12] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
-		protection_map[13] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
-		protection_map[14] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
-		protection_map[15] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
+		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | __READABLE);
+		protection_map[12]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
+		protection_map[13]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
+		protection_map[14]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
+		protection_map[15]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
+
 
 	} else {
 		protection_map[0] = PAGE_NONE;
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index e8cbc2e795d5..ef9c5fa8673e 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -377,14 +377,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
  * To be differentiate with macro pte_mkyoung, this macro is used on platforms
  * where software maintains page access bit.
  */
-#ifndef pte_sw_mkyoung
-static inline pte_t pte_sw_mkyoung(pte_t pte)
-{
-	return pte;
-}
-#define pte_sw_mkyoung	pte_sw_mkyoung
-#endif
-
 #ifndef pte_savedwrite
 #define pte_savedwrite pte_write
 #endif
diff --git a/mm/memory.c b/mm/memory.c
index 602f4283122f..5100ab5bcf77 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2705,7 +2705,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
 		}
 		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
 		entry = mk_pte(new_page, vma->vm_page_prot);
-		entry = pte_sw_mkyoung(entry);
 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 		/*
 		 * Clear the pte entry and flush it first, before updating the
@@ -3386,7 +3385,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 	__SetPageUptodate(page);
 
 	entry = mk_pte(page, vma->vm_page_prot);
-	entry = pte_sw_mkyoung(entry);
 	if (vma->vm_flags & VM_WRITE)
 		entry = pte_mkwrite(pte_mkdirty(entry));
 
@@ -3661,7 +3659,6 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page)
 
 	flush_icache_page(vma, page);
 	entry = mk_pte(page, vma->vm_page_prot);
-	entry = pte_sw_mkyoung(entry);
 	if (write)
 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 	/* copy-on-write page */
-- 
2.17.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH V3] MIPS: make userspace mapping young by default
  2020-09-19  7:47 [PATCH V3] MIPS: make userspace mapping young by default Huang Pei
@ 2020-09-28  6:39 ` Huang Pei
  2020-10-02 12:35 ` Thomas Bogendoerfer
  1 sibling, 0 replies; 4+ messages in thread
From: Huang Pei @ 2020-09-28  6:39 UTC (permalink / raw)
  To: Thomas Bogendoerfer, ambrosehua
  Cc: Bibo Mao, Andrew Morton, linux-mips, linux-arch, linux-mm,
	Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu, Gao Juxin,
	Fuxin Zhang, Huacai Chen

On Sat, Sep 19, 2020 at 03:47:31PM +0800, Huang Pei wrote:

Ping?
> MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
> the second TLB Invalid exception is just triggered by __update_tlb from
> do_page_fault writing tlb without _PAGE_VALID set. With this patch, it
> only take 1 TLB Miss + 1 TLB Invalid exceptions
> 
> This version removes pte_sw_mkyoung without polluting MM code and makes
> page fault delay of MIPS on par with other architecture and covers both
> no-RIXI and RIXI MIPS CPUS
> 
> [1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
> -maobibo@loongson.cn/
> ---
> V3:
> - reformat with whitespace cleaned up following Thomas's advice
> V2:
> - remove unused asm-generic definition of pte_sw_mkyoung following Mao's
> advice
> ---
> Co-developed-by: Huang Pei <huangpei@loongson.cn>
> Signed-off-by: Huang Pei <huangpei@loongson.cn>
> Co-developed-by: Bibo Mao <maobibo@loonson.cn>
> ---
>  arch/mips/include/asm/pgtable.h | 10 ++++------
>  arch/mips/mm/cache.c            | 25 +++++++++++++------------
>  include/linux/pgtable.h         |  8 --------
>  mm/memory.c                     |  3 ---
>  4 files changed, 17 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index dd7a0f552cac..931fb35730f0 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -27,11 +27,11 @@ struct vm_area_struct;
>  
>  #define PAGE_NONE	__pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
>  				 _page_cachable_default)
> -#define PAGE_SHARED	__pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> -				 _page_cachable_default)
> +#define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> +				 __READABLE | _page_cachable_default)
>  #define PAGE_COPY	__pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> -				 _page_cachable_default)
> -#define PAGE_READONLY	__pgprot(_PAGE_PRESENT | \
> +				 __READABLE | _page_cachable_default)
> +#define PAGE_READONLY	__pgprot(_PAGE_PRESENT |  __READABLE | \
>  				 _page_cachable_default)
>  #define PAGE_KERNEL	__pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
>  				 _PAGE_GLOBAL | _page_cachable_default)
> @@ -414,8 +414,6 @@ static inline pte_t pte_mkyoung(pte_t pte)
>  	return pte;
>  }
>  
> -#define pte_sw_mkyoung	pte_mkyoung
> -
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
>  static inline int pte_huge(pte_t pte)	{ return pte_val(pte) & _PAGE_HUGE; }
>  
> diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> index 3e81ba000096..ed75f2871aad 100644
> --- a/arch/mips/mm/cache.c
> +++ b/arch/mips/mm/cache.c
> @@ -159,22 +159,23 @@ static inline void setup_protection_map(void)
>  {
>  	if (cpu_has_rixi) {
>  		protection_map[0]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> +		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
>  		protection_map[2]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> -		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> +		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
>  
>  		protection_map[8]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> +		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
>  		protection_map[10] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | _PAGE_NO_READ);
> -		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
> -		protection_map[12] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[13] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[14] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> -		protection_map[15] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> +		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | __READABLE);
> +		protection_map[12]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[13]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[14]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +		protection_map[15]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +
>  
>  	} else {
>  		protection_map[0] = PAGE_NONE;
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index e8cbc2e795d5..ef9c5fa8673e 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -377,14 +377,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
>   * To be differentiate with macro pte_mkyoung, this macro is used on platforms
>   * where software maintains page access bit.
>   */
> -#ifndef pte_sw_mkyoung
> -static inline pte_t pte_sw_mkyoung(pte_t pte)
> -{
> -	return pte;
> -}
> -#define pte_sw_mkyoung	pte_sw_mkyoung
> -#endif
> -
>  #ifndef pte_savedwrite
>  #define pte_savedwrite pte_write
>  #endif
> diff --git a/mm/memory.c b/mm/memory.c
> index 602f4283122f..5100ab5bcf77 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2705,7 +2705,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
>  		}
>  		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
>  		entry = mk_pte(new_page, vma->vm_page_prot);
> -		entry = pte_sw_mkyoung(entry);
>  		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  		/*
>  		 * Clear the pte entry and flush it first, before updating the
> @@ -3386,7 +3385,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>  	__SetPageUptodate(page);
>  
>  	entry = mk_pte(page, vma->vm_page_prot);
> -	entry = pte_sw_mkyoung(entry);
>  	if (vma->vm_flags & VM_WRITE)
>  		entry = pte_mkwrite(pte_mkdirty(entry));
>  
> @@ -3661,7 +3659,6 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page)
>  
>  	flush_icache_page(vma, page);
>  	entry = mk_pte(page, vma->vm_page_prot);
> -	entry = pte_sw_mkyoung(entry);
>  	if (write)
>  		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  	/* copy-on-write page */
> -- 
> 2.17.1
> 


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH V3] MIPS: make userspace mapping young by default
  2020-09-19  7:47 [PATCH V3] MIPS: make userspace mapping young by default Huang Pei
  2020-09-28  6:39 ` Huang Pei
@ 2020-10-02 12:35 ` Thomas Bogendoerfer
  2020-10-08  3:30   ` Huang Pei
  1 sibling, 1 reply; 4+ messages in thread
From: Thomas Bogendoerfer @ 2020-10-02 12:35 UTC (permalink / raw)
  To: Huang Pei
  Cc: ambrosehua, Bibo Mao, Andrew Morton, linux-mips, linux-arch,
	linux-mm, Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu,
	Gao Juxin, Fuxin Zhang, Huacai Chen

On Sat, Sep 19, 2020 at 03:47:31PM +0800, Huang Pei wrote:
> MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
> the second TLB Invalid exception is just triggered by __update_tlb from
> do_page_fault writing tlb without _PAGE_VALID set. With this patch, it
> only take 1 TLB Miss + 1 TLB Invalid exceptions
> 
> This version removes pte_sw_mkyoung without polluting MM code and makes
> page fault delay of MIPS on par with other architecture and covers both
> no-RIXI and RIXI MIPS CPUS
> 
> [1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
> -maobibo@loongson.cn/
> ---
> V3:
> - reformat with whitespace cleaned up following Thomas's advice
> V2:
> - remove unused asm-generic definition of pte_sw_mkyoung following Mao's
> advice
> ---
> Co-developed-by: Huang Pei <huangpei@loongson.cn>
> Signed-off-by: Huang Pei <huangpei@loongson.cn>
> Co-developed-by: Bibo Mao <maobibo@loonson.cn>
> ---
>  arch/mips/include/asm/pgtable.h | 10 ++++------
>  arch/mips/mm/cache.c            | 25 +++++++++++++------------
>  include/linux/pgtable.h         |  8 --------
>  mm/memory.c                     |  3 ---
>  4 files changed, 17 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index dd7a0f552cac..931fb35730f0 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -27,11 +27,11 @@ struct vm_area_struct;
>  
>  #define PAGE_NONE	__pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
>  				 _page_cachable_default)
> -#define PAGE_SHARED	__pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> -				 _page_cachable_default)
> +#define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> +				 __READABLE | _page_cachable_default)

you are still doing a white space changes here. 

>  #define PAGE_COPY	__pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> -				 _page_cachable_default)
> -#define PAGE_READONLY	__pgprot(_PAGE_PRESENT | \
> +				 __READABLE | _page_cachable_default)
> +#define PAGE_READONLY	__pgprot(_PAGE_PRESENT |  __READABLE | \

I've grepped for usage of PAGE_SHARED and PAGE_READONLY and found
arch/mips/kvm/mmu.c and arch/mips/kernel/vdso.c. I wonder

1. Is this usage correct or should we use protection_map[X] ?
2. Are this still correct after the change in this patch ?

Right now I'm in favour to fist clean up asm/pgtable.h to get rid
of all unneeded PAGE_XXX defines and make mm/cache.c rixi part
more readable before applying this patch.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH V3] MIPS: make userspace mapping young by default
  2020-10-02 12:35 ` Thomas Bogendoerfer
@ 2020-10-08  3:30   ` Huang Pei
  0 siblings, 0 replies; 4+ messages in thread
From: Huang Pei @ 2020-10-08  3:30 UTC (permalink / raw)
  To: Thomas Bogendoerfer
  Cc: ambrosehua, Bibo Mao, Andrew Morton, linux-mips, linux-arch,
	linux-mm, Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu,
	Gao Juxin, Fuxin Zhang, Huacai Chen

On Fri, Oct 02, 2020 at 02:35:03PM +0200, Thomas Bogendoerfer wrote:
Hi, 
> On Sat, Sep 19, 2020 at 03:47:31PM +0800, Huang Pei wrote:
> > MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
> > the second TLB Invalid exception is just triggered by __update_tlb from
> > do_page_fault writing tlb without _PAGE_VALID set. With this patch, it
> > only take 1 TLB Miss + 1 TLB Invalid exceptions
> > 
> > This version removes pte_sw_mkyoung without polluting MM code and makes
> > page fault delay of MIPS on par with other architecture and covers both
> > no-RIXI and RIXI MIPS CPUS
> > 
> > [1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
> > -maobibo@loongson.cn/
> > ---
> > V3:
> > - reformat with whitespace cleaned up following Thomas's advice
> > V2:
> > - remove unused asm-generic definition of pte_sw_mkyoung following Mao's
> > advice
> > ---
> > Co-developed-by: Huang Pei <huangpei@loongson.cn>
> > Signed-off-by: Huang Pei <huangpei@loongson.cn>
> > Co-developed-by: Bibo Mao <maobibo@loonson.cn>
> > ---
> >  arch/mips/include/asm/pgtable.h | 10 ++++------
> >  arch/mips/mm/cache.c            | 25 +++++++++++++------------
> >  include/linux/pgtable.h         |  8 --------
> >  mm/memory.c                     |  3 ---
> >  4 files changed, 17 insertions(+), 29 deletions(-)
> > 
> > diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> > index dd7a0f552cac..931fb35730f0 100644
> > --- a/arch/mips/include/asm/pgtable.h
> > +++ b/arch/mips/include/asm/pgtable.h
> > @@ -27,11 +27,11 @@ struct vm_area_struct;
> >  
> >  #define PAGE_NONE	__pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
> >  				 _page_cachable_default)
> > -#define PAGE_SHARED	__pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > -				 _page_cachable_default)
> > +#define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > +				 __READABLE | _page_cachable_default)
> 
> you are still doing a white space changes here. 
> 
> >  #define PAGE_COPY	__pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> > -				 _page_cachable_default)
> > -#define PAGE_READONLY	__pgprot(_PAGE_PRESENT | \
> > +				 __READABLE | _page_cachable_default)
> > +#define PAGE_READONLY	__pgprot(_PAGE_PRESENT |  __READABLE | \
> 
sorry, my bad
> I've grepped for usage of PAGE_SHARED and PAGE_READONLY and found
> arch/mips/kvm/mmu.c and arch/mips/kernel/vdso.c. I wonder
> 
for arch/mips/kvm/mmu.c, the comment says:
...
	/* Also set valid and dirty, so refill handler doesn't have to */
	*ptep = pte_mkyoung(pte_mkdirty(pfn_pte(pfn, PAGE_SHARED)));
...
the net effect is the same, dirty and valid, so I think it is ok;

for arch/mips/kernel/vdso.c, both mappings are kernel mapping, which
means the physical memory(or io memory) is already allocated and will not
be reclaimed by kernel.
       
> 1. Is this usage correct or should we use protection_map[X] ?
> 2. Are this still correct after the change in this patch ?
> 
> Right now I'm in favour to fist clean up asm/pgtable.h to get rid
> of all unneeded PAGE_XXX defines and make mm/cache.c rixi part
> more readable before applying this patch.
>
I think we can clean up rixi part of mm/cache.c after this patch, or
within V4;

> Thomas.
> 
> -- 
> Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
> good idea.                                                [ RFC1925, 2.3 ]


^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-19  7:47 [PATCH V3] MIPS: make userspace mapping young by default Huang Pei
2020-09-28  6:39 ` Huang Pei
2020-10-02 12:35 ` Thomas Bogendoerfer
2020-10-08  3:30   ` Huang Pei

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