Commit 5383cc6e authored by Steve Capper's avatar Steve Capper Committed by Will Deacon
Browse files

arm64: mm: Introduce vabits_actual 



In order to support 52-bit kernel addresses detectable at boot time, one
needs to know the actual VA_BITS detected. A new variable vabits_actual
is introduced in this commit and employed for the KVM hypervisor layout,
KASAN, fault handling and phys-to/from-virt translation where there
would normally be compile time constants.

In order to maintain performance in phys_to_virt, another variable
physvirt_offset is introduced.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarSteve Capper <steve.capper@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 90ec95cd

arch/arm64/include/asm/kasan.h

+1 −1
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ 
 *				(1ULL << (64 - KASAN_SHADOW_SCALE_SHIFT))

 */

#define _KASAN_SHADOW_START(va)	(KASAN_SHADOW_END - (1UL << ((va) - KASAN_SHADOW_SCALE_SHIFT)))

#define KASAN_SHADOW_START      _KASAN_SHADOW_START(VA_BITS)

#define KASAN_SHADOW_START      _KASAN_SHADOW_START(vabits_actual)



void kasan_init(void);

void kasan_copy_shadow(pgd_t *pgdir);

arch/arm64/include/asm/memory.h

+6 −5
Original line number Diff line number Diff line
@@ -37,8 +37,6 @@ 
 * VA_START - the first kernel virtual address.

 */

#define VA_BITS			(CONFIG_ARM64_VA_BITS)

#define VA_START		(UL(0xffffffffffffffff) - \

	(UL(1) << (VA_BITS - 1)) + 1)

#define PAGE_OFFSET		(UL(0xffffffffffffffff) - \

	(UL(1) << VA_BITS) + 1)

#define KIMAGE_VADDR		(MODULES_END)
@@ -166,10 +164,13 @@ 
#endif



#ifndef __ASSEMBLY__

extern u64			vabits_actual;

#define VA_START		(_VA_START(vabits_actual))



#include <linux/bitops.h>

#include <linux/mmdebug.h>



extern s64			physvirt_offset;

extern s64			memstart_addr;

/* PHYS_OFFSET - the physical address of the start of memory. */

#define PHYS_OFFSET		({ VM_BUG_ON(memstart_addr & 1); memstart_addr; })
@@ -240,9 +241,9 @@ static inline const void *__tag_set(const void *addr, u8 tag) 
 * space. Testing the top bit for the start of the region is a

 * sufficient check.

 */

#define __is_lm_address(addr)	(!((addr) & BIT(VA_BITS - 1)))

#define __is_lm_address(addr)	(!((addr) & BIT(vabits_actual - 1)))



#define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)

#define __lm_to_phys(addr)	(((addr) + physvirt_offset))

#define __kimg_to_phys(addr)	((addr) - kimage_voffset)



#define __virt_to_phys_nodebug(x) ({					\
@@ -261,7 +262,7 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x); 
#define __phys_addr_symbol(x)	__pa_symbol_nodebug(x)

#endif



#define __phys_to_virt(x)	((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET)

#define __phys_to_virt(x)	((unsigned long)((x) - physvirt_offset))

#define __phys_to_kimg(x)	((unsigned long)((x) + kimage_voffset))



/*

arch/arm64/include/asm/mmu_context.h

+1 −1
Original line number Diff line number Diff line
@@ -95,7 +95,7 @@ static inline void __cpu_set_tcr_t0sz(unsigned long t0sz) 
	isb();

}



#define cpu_set_default_tcr_t0sz()	__cpu_set_tcr_t0sz(TCR_T0SZ(VA_BITS))

#define cpu_set_default_tcr_t0sz()	__cpu_set_tcr_t0sz(TCR_T0SZ(vabits_actual))

#define cpu_set_idmap_tcr_t0sz()	__cpu_set_tcr_t0sz(idmap_t0sz)



/*

arch/arm64/kernel/head.S

+5 −0
Original line number Diff line number Diff line
@@ -321,6 +321,11 @@ __create_page_tables: 
	dmb	sy

	dc	ivac, x6		// Invalidate potentially stale cache line



	adr_l	x6, vabits_actual

	str	x5, [x6]

	dmb	sy

	dc	ivac, x6		// Invalidate potentially stale cache line



	/*

	 * VA_BITS may be too small to allow for an ID mapping to be created

	 * that covers system RAM if that is located sufficiently high in the

arch/arm64/kvm/va_layout.c

+7 −7
Original line number Diff line number Diff line
@@ -29,25 +29,25 @@ static void compute_layout(void) 
	int kva_msb;



	/* Where is my RAM region? */

	hyp_va_msb  = idmap_addr & BIT(VA_BITS - 1);

	hyp_va_msb ^= BIT(VA_BITS - 1);

	hyp_va_msb  = idmap_addr & BIT(vabits_actual - 1);

	hyp_va_msb ^= BIT(vabits_actual - 1);



	kva_msb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^

			(u64)(high_memory - 1));



	if (kva_msb == (VA_BITS - 1)) {

	if (kva_msb == (vabits_actual - 1)) {

		/*

		 * No space in the address, let's compute the mask so

		 * that it covers (VA_BITS - 1) bits, and the region

		 * that it covers (vabits_actual - 1) bits, and the region

		 * bit. The tag stays set to zero.

		 */

		va_mask  = BIT(VA_BITS - 1) - 1;

		va_mask  = BIT(vabits_actual - 1) - 1;

		va_mask |= hyp_va_msb;

	} else {

		/*

		 * We do have some free bits to insert a random tag.

		 * Hyp VAs are now created from kernel linear map VAs

		 * using the following formula (with V == VA_BITS):

		 * using the following formula (with V == vabits_actual):

		 *

		 *  63 ... V |     V-1    | V-2 .. tag_lsb | tag_lsb - 1 .. 0

		 *  ---------------------------------------------------------
@@ -55,7 +55,7 @@ static void compute_layout(void) 
		 */

		tag_lsb = kva_msb;

		va_mask = GENMASK_ULL(tag_lsb - 1, 0);

		tag_val = get_random_long() & GENMASK_ULL(VA_BITS - 2, tag_lsb);

		tag_val = get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb);

		tag_val |= hyp_va_msb;

		tag_val >>= tag_lsb;

	}

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