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arm64: tlb: Use the TLBI RANGE feature in arm64
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Add __TLBI_VADDR_RANGE macro and rewrite __flush_tlb_range().

When cpu supports TLBI feature, the minimum range granularity is
decided by 'scale', so we can not flush all pages by one instruction
in some cases.

For example, when the pages = 0xe81a, let's start 'scale' from
maximum, and find right 'num' for each 'scale':

1. scale = 3, we can flush no pages because the minimum range is
   2^(5*3 + 1) = 0x10000.
2. scale = 2, the minimum range is 2^(5*2 + 1) = 0x800, we can
   flush 0xe800 pages this time, the num = 0xe800/0x800 - 1 = 0x1c.
   Remaining pages is 0x1a;
3. scale = 1, the minimum range is 2^(5*1 + 1) = 0x40, no page
   can be flushed.
4. scale = 0, we flush the remaining 0x1a pages, the num =
   0x1a/0x2 - 1 = 0xd.

However, in most scenarios, the pages = 1 when flush_tlb_range() is
called. Start from scale = 3 or other proper value (such as scale =
ilog2(pages)), will incur extra overhead.
So increase 'scale' from 0 to maximum, the flush order is exactly
opposite to the example.

Signed-off-by: Zhenyu Ye <yezhenyu2@huawei.com>
Link: https://lore.kernel.org/r/20200715071945.897-4-yezhenyu2@huawei.com
[catalin.marinas@arm.com: removed unnecessary masks in __TLBI_VADDR_RANGE]
[catalin.marinas@arm.com: __TLB_RANGE_NUM subtracts 1]
[catalin.marinas@arm.com: minor adjustments to the comments]
[catalin.marinas@arm.com: introduce system_supports_tlb_range()]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Zhenyu Ye authored and Catalin Marinas committed Jul 15, 2020
1 parent 7c78f67 commit d1d3aa9
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Showing 2 changed files with 131 additions and 29 deletions.
6 changes: 6 additions & 0 deletions arch/arm64/include/asm/cpufeature.h
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Original file line number Diff line number Diff line change
Expand Up @@ -692,6 +692,12 @@ static inline bool system_supports_bti(void)
return IS_ENABLED(CONFIG_ARM64_BTI) && cpus_have_const_cap(ARM64_BTI);
}

static inline bool system_supports_tlb_range(void)
{
return IS_ENABLED(CONFIG_ARM64_TLB_RANGE) &&
cpus_have_const_cap(ARM64_HAS_TLB_RANGE);
}

#define ARM64_BP_HARDEN_UNKNOWN -1
#define ARM64_BP_HARDEN_WA_NEEDED 0
#define ARM64_BP_HARDEN_NOT_REQUIRED 1
Expand Down
154 changes: 125 additions & 29 deletions arch/arm64/include/asm/tlbflush.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,31 @@
__ta; \
})

/*
* Get translation granule of the system, which is decided by
* PAGE_SIZE. Used by TTL.
* - 4KB : 1
* - 16KB : 2
* - 64KB : 3
*/
#define TLBI_TTL_TG_4K 1
#define TLBI_TTL_TG_16K 2
#define TLBI_TTL_TG_64K 3

static inline unsigned long get_trans_granule(void)
{
switch (PAGE_SIZE) {
case SZ_4K:
return TLBI_TTL_TG_4K;
case SZ_16K:
return TLBI_TTL_TG_16K;
case SZ_64K:
return TLBI_TTL_TG_64K;
default:
return 0;
}
}

/*
* Level-based TLBI operations.
*
Expand All @@ -73,29 +98,14 @@
* in asm/stage2_pgtable.h.
*/
#define TLBI_TTL_MASK GENMASK_ULL(47, 44)
#define TLBI_TTL_TG_4K 1
#define TLBI_TTL_TG_16K 2
#define TLBI_TTL_TG_64K 3

#define __tlbi_level(op, addr, level) do { \
u64 arg = addr; \
\
if (cpus_have_const_cap(ARM64_HAS_ARMv8_4_TTL) && \
level) { \
u64 ttl = level & 3; \
\
switch (PAGE_SIZE) { \
case SZ_4K: \
ttl |= TLBI_TTL_TG_4K << 2; \
break; \
case SZ_16K: \
ttl |= TLBI_TTL_TG_16K << 2; \
break; \
case SZ_64K: \
ttl |= TLBI_TTL_TG_64K << 2; \
break; \
} \
\
ttl |= get_trans_granule() << 2; \
arg &= ~TLBI_TTL_MASK; \
arg |= FIELD_PREP(TLBI_TTL_MASK, ttl); \
} \
Expand All @@ -108,6 +118,44 @@
__tlbi_level(op, (arg | USER_ASID_FLAG), level); \
} while (0)

/*
* This macro creates a properly formatted VA operand for the TLB RANGE.
* The value bit assignments are:
*
* +----------+------+-------+-------+-------+----------------------+
* | ASID | TG | SCALE | NUM | TTL | BADDR |
* +-----------------+-------+-------+-------+----------------------+
* |63 48|47 46|45 44|43 39|38 37|36 0|
*
* The address range is determined by below formula:
* [BADDR, BADDR + (NUM + 1) * 2^(5*SCALE + 1) * PAGESIZE)
*
*/
#define __TLBI_VADDR_RANGE(addr, asid, scale, num, ttl) \
({ \
unsigned long __ta = (addr) >> PAGE_SHIFT; \
__ta &= GENMASK_ULL(36, 0); \
__ta |= (unsigned long)(ttl) << 37; \
__ta |= (unsigned long)(num) << 39; \
__ta |= (unsigned long)(scale) << 44; \
__ta |= get_trans_granule() << 46; \
__ta |= (unsigned long)(asid) << 48; \
__ta; \
})

/* These macros are used by the TLBI RANGE feature. */
#define __TLBI_RANGE_PAGES(num, scale) \
((unsigned long)((num) + 1) << (5 * (scale) + 1))
#define MAX_TLBI_RANGE_PAGES __TLBI_RANGE_PAGES(31, 3)

/*
* Generate 'num' values from -1 to 30 with -1 rejected by the
* __flush_tlb_range() loop below.
*/
#define TLBI_RANGE_MASK GENMASK_ULL(4, 0)
#define __TLBI_RANGE_NUM(pages, scale) \
((((pages) >> (5 * (scale) + 1)) & TLBI_RANGE_MASK) - 1)

/*
* TLB Invalidation
* ================
Expand Down Expand Up @@ -231,32 +279,80 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
unsigned long stride, bool last_level,
int tlb_level)
{
int num = 0;
int scale = 0;
unsigned long asid = ASID(vma->vm_mm);
unsigned long addr;
unsigned long pages;

start = round_down(start, stride);
end = round_up(end, stride);
pages = (end - start) >> PAGE_SHIFT;

if ((end - start) >= (MAX_TLBI_OPS * stride)) {
/*
* When not uses TLB range ops, we can handle up to
* (MAX_TLBI_OPS - 1) pages;
* When uses TLB range ops, we can handle up to
* (MAX_TLBI_RANGE_PAGES - 1) pages.
*/
if ((!system_supports_tlb_range() &&
(end - start) >= (MAX_TLBI_OPS * stride)) ||
pages >= MAX_TLBI_RANGE_PAGES) {
flush_tlb_mm(vma->vm_mm);
return;
}

/* Convert the stride into units of 4k */
stride >>= 12;
dsb(ishst);

start = __TLBI_VADDR(start, asid);
end = __TLBI_VADDR(end, asid);
/*
* When the CPU does not support TLB range operations, flush the TLB
* entries one by one at the granularity of 'stride'. If the the TLB
* range ops are supported, then:
*
* 1. If 'pages' is odd, flush the first page through non-range
* operations;
*
* 2. For remaining pages: the minimum range granularity is decided
* by 'scale', so multiple range TLBI operations may be required.
* Start from scale = 0, flush the corresponding number of pages
* ((num+1)*2^(5*scale+1) starting from 'addr'), then increase it
* until no pages left.
*
* Note that certain ranges can be represented by either num = 31 and
* scale or num = 0 and scale + 1. The loop below favours the latter
* since num is limited to 30 by the __TLBI_RANGE_NUM() macro.
*/
while (pages > 0) {
if (!system_supports_tlb_range() ||
pages % 2 == 1) {
addr = __TLBI_VADDR(start, asid);
if (last_level) {
__tlbi_level(vale1is, addr, tlb_level);
__tlbi_user_level(vale1is, addr, tlb_level);
} else {
__tlbi_level(vae1is, addr, tlb_level);
__tlbi_user_level(vae1is, addr, tlb_level);
}
start += stride;
pages -= stride >> PAGE_SHIFT;
continue;
}

dsb(ishst);
for (addr = start; addr < end; addr += stride) {
if (last_level) {
__tlbi_level(vale1is, addr, tlb_level);
__tlbi_user_level(vale1is, addr, tlb_level);
} else {
__tlbi_level(vae1is, addr, tlb_level);
__tlbi_user_level(vae1is, addr, tlb_level);
num = __TLBI_RANGE_NUM(pages, scale);
if (num >= 0) {
addr = __TLBI_VADDR_RANGE(start, asid, scale,
num, tlb_level);
if (last_level) {
__tlbi(rvale1is, addr);
__tlbi_user(rvale1is, addr);
} else {
__tlbi(rvae1is, addr);
__tlbi_user(rvae1is, addr);
}
start += __TLBI_RANGE_PAGES(num, scale) << PAGE_SHIFT;
pages -= __TLBI_RANGE_PAGES(num, scale);
}
scale++;
}
dsb(ish);
}
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