Commit aec98260 authored Dec 06, 2021 by Christophe Leroy Committed by Michael Ellerman Jan 24, 2022

powerpc/fixmap: Fix VM debug warning on unmap



Unmapping a fixmap entry is done by calling __set_fixmap()
with FIXMAP_PAGE_CLEAR as flags.

Today, powerpc __set_fixmap() calls map_kernel_page().

map_kernel_page() is not happy when called a second time
for the same page.

	WARNING: CPU: 0 PID: 1 at arch/powerpc/mm/pgtable.c:194 set_pte_at+0xc/0x1e8
	CPU: 0 PID: 1 Comm: swapper Not tainted 5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty #682
	NIP:  c0017cd4 LR: c00187f0 CTR: 00000010
	REGS: e1011d50 TRAP: 0700   Not tainted  (5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty)
	MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 42000208  XER: 00000000

	GPR00: c0165fec e1011e10 c14c0000 c0ee2550 ff800000 c0f3d000 00000000 c001686c
	GPR08: 00001000 b00045a9 00000001 c0f58460 c0f50000 00000000 c0007e10 00000000
	GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
	GPR24: 00000000 00000000 c0ee2550 00000000 c0f57000 00000ff8 00000000 ff800000
	NIP [c0017cd4] set_pte_at+0xc/0x1e8
	LR [c00187f0] map_kernel_page+0x9c/0x100
	Call Trace:
	[e1011e10] [c0736c68] vsnprintf+0x358/0x6c8 (unreliable)
	[e1011e30] [c0165fec] __set_fixmap+0x30/0x44
	[e1011e40] [c0c13bdc] early_iounmap+0x11c/0x170
	[e1011e70] [c0c06cb0] ioremap_legacy_serial_console+0x88/0xc0
	[e1011e90] [c0c03634] do_one_initcall+0x80/0x178
	[e1011ef0] [c0c0385c] kernel_init_freeable+0xb4/0x250
	[e1011f20] [c0007e34] kernel_init+0x24/0x140
	[e1011f30] [c0016268] ret_from_kernel_thread+0x5c/0x64
	Instruction dump:
	7fe3fb78 48019689 80010014 7c630034 83e1000c 5463d97e 7c0803a6 38210010
	4e800020 81250000 712a0001 41820008 <0fe00000> 9421ffe0 93e1001c 48000030

Implement unmap_kernel_page() which clears an existing pte.

Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b0b752f6f6ecc60653e873f385c6f0dce4e9ab6a.1638789098.git.christophe.leroy@csgroup.eu

parent dd81e1c7

arch/powerpc/include/asm/book3s/32/pgtable.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -178,6 +178,7 @@ static inline bool pte_user(pte_t pte)
		#ifndef __ASSEMBLY__

		int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
		void unmap_kernel_page(unsigned long va);

		#endif /* !__ASSEMBLY__ */

arch/powerpc/include/asm/book3s/64/pgtable.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -1082,6 +1082,8 @@ static inline int map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t p
		return hash__map_kernel_page(ea, pa, prot);
		}

		void unmap_kernel_page(unsigned long va);

		static inline int __meminit vmemmap_create_mapping(unsigned long start,
		unsigned long page_size,
		unsigned long phys)

arch/powerpc/include/asm/fixmap.h

+4 −2

Original line number	Diff line number	Diff line
		@@ -111,8 +111,10 @@ static inline void __set_fixmap(enum fixed_addresses idx,
		BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
		else if (WARN_ON(idx >= __end_of_fixed_addresses))
		return;

		if (pgprot_val(flags))
		map_kernel_page(__fix_to_virt(idx), phys, flags);
		else
		unmap_kernel_page(__fix_to_virt(idx));
		}

		#define __early_set_fixmap __set_fixmap

arch/powerpc/include/asm/nohash/32/pgtable.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -64,6 +64,7 @@ extern int icache_44x_need_flush;
		#ifndef __ASSEMBLY__

		int map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot);
		void unmap_kernel_page(unsigned long va);

		#endif /* !__ASSEMBLY__ */

arch/powerpc/include/asm/nohash/64/pgtable.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -308,6 +308,7 @@ static inline void __ptep_set_access_flags(struct vm_area_struct *vma,
		#define __swp_entry_to_pte(x) __pte((x).val)

		int map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot);
		void unmap_kernel_page(unsigned long va);
		extern int __meminit vmemmap_create_mapping(unsigned long start,
		unsigned long page_size,
		unsigned long phys);