Commit acca4f4d authored by Paul Mundt's avatar Paul Mundt
Browse files

sh: Handle fixmap TLB eviction more coherently. 



There was a race in the kmap_coherent() implementation. While we
guarded against preemption, there was nothing preventing eviction of
the pre-faulted fixmap entry from the UTLB. Under certain workloads
this would result in the fixmap entries used for cache colouring being
evicted from the UTLB in the midst of a copy_page().

In addition to pre-faulting, we also make sure to preserve the PTEs
in the kernel page table and introduce a cached PTE for kmap_coherent()
usage. This follows a similar change on MIPS ("[MIPS] Fix aliasing bug
in copy_to_user_page / copy_from_user_page").

Reported-by: default avatarHideo Saito <saito@densan.co.jp>
Reported-by: default avatarCHIKAMA Masaki <masaki.chikama@gmail.com>
Tested-by: default avatarYoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
parent f7160c75

arch/sh/include/asm/pgtable.h

+6 −0
Original line number Diff line number Diff line
@@ -148,6 +148,12 @@ extern void paging_init(void); 
extern void page_table_range_init(unsigned long start, unsigned long end,

				  pgd_t *pgd);



#if !defined(CONFIG_CACHE_OFF) && defined(CONFIG_CPU_SH4) && defined(CONFIG_MMU)

extern void kmap_coherent_init(void);

#else

#define kmap_coherent_init()	do { } while (0)

#endif



#include <asm-generic/pgtable.h>



#endif /* __ASM_SH_PGTABLE_H */

arch/sh/mm/init.c

+9 −3
Original line number Diff line number Diff line
@@ -137,6 +137,7 @@ void __init page_table_range_init(unsigned long start, unsigned long end, 
void __init paging_init(void)

{

	unsigned long max_zone_pfns[MAX_NR_ZONES];

	unsigned long vaddr;

	int nid;



	/* We don't need to map the kernel through the TLB, as
@@ -148,10 +149,15 @@ void __init paging_init(void) 
	 * check for a null value. */

	set_TTB(swapper_pg_dir);



	/* Populate the relevant portions of swapper_pg_dir so that

	/*

	 * Populate the relevant portions of swapper_pg_dir so that

	 * we can use the fixmap entries without calling kmalloc.

	 * pte's will be filled in by __set_fixmap(). */

	page_table_range_init(FIXADDR_START, FIXADDR_TOP, swapper_pg_dir);

	 * pte's will be filled in by __set_fixmap().

	 */

	vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;

	page_table_range_init(vaddr, 0, swapper_pg_dir);



	kmap_coherent_init();



	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));

arch/sh/mm/pg-sh4.c

+17 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
 * Released under the terms of the GNU GPL v2.0.

 */

#include <linux/mm.h>

#include <linux/init.h>

#include <linux/mutex.h>

#include <linux/fs.h>

#include <linux/highmem.h>
@@ -16,6 +17,20 @@ 


#define CACHE_ALIAS (current_cpu_data.dcache.alias_mask)



#define kmap_get_fixmap_pte(vaddr)                                     \

	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))



static pte_t *kmap_coherent_pte;



void __init kmap_coherent_init(void)

{

	unsigned long vaddr;



	/* cache the first coherent kmap pte */

	vaddr = __fix_to_virt(FIX_CMAP_BEGIN);

	kmap_coherent_pte = kmap_get_fixmap_pte(vaddr);

}



static inline void *kmap_coherent(struct page *page, unsigned long addr)

{

	enum fixed_addresses idx;
@@ -34,6 +49,8 @@ static inline void *kmap_coherent(struct page *page, unsigned long addr) 


	update_mmu_cache(NULL, vaddr, pte);



	set_pte(kmap_coherent_pte - (FIX_CMAP_END - idx), pte);



	return (void *)vaddr;

}

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