Re: [PATCH v1 2/2] arm64: tlb: Use the TLBI RANGE feature in arm64
Hi Catalin,
On 2020/7/10 1:36, Catalin Marinas wrote:
> On Thu, Jul 09, 2020 at 05:10:54PM +0800, Zhenyu Ye wrote:
>> #define __tlbi_level(op, addr, level) do { \
>> u64 arg = addr; \
>> \
>> if (cpus_have_const_cap(ARM64_HAS_ARMv8_4_TTL) && \
>> +!cpus_have_const_cap(ARM64_HAS_TLBI_RANGE) && \
>> 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); \
>> } \
>
> I think checking for !ARM64_HAS_TLBI_RANGE here is incorrect. I can see
> why you attempted this since the range and classic ops have a different
> position for the level but now you are not passing the TTL at all for
> the classic TLBI. It's also inconsistent to have the range ops get the
> level in the addr argument while the classic ops added in the
> __tlbi_level macro.
>
You are right, this is really a serious problem. But this can be avoided
after removing the check for ARM64_HAS_TLBI_RANGE and dropping the
__tlbi_last_level.
Just call __tlbi() and __tlbi_user() when doing range ops.
> I'd rather have two sets of macros, __tlbi_level and __tlbi_range_level,
> called depending on whether you use classic or range ops.
>
Then we have to add __tlbi_user_range_level, too. And if we move the num
and scale out of __TLBI_VADDR_RANGE, the __TLBI_VADDR_RANGE macro will make
little sense (addr and asid also can be moved out).
__TLBI_VADDR macro is defined to create a properly formatted VA operand for
the TLBI, then how about add the level to __TLBI_VADDR, just like:
#define __TLBI_VADDR(addr, asid, level) \
({ \
unsigned long __ta = (addr) >> 12; \
__ta &= GENMASK_ULL(43, 0); \
__ta |= (unsigned long)(asid) << 48;\
if (cpus_have_const_cap(ARM64_HAS_ARMv8_4_TTL)) { \
u64 ttl = get_trans_granule() << 2 + level & 3; \
__ta |= ttl << 44; \
} \
__ta; \
})
Then we should make sure __TLBI_VADDR is used for all TLBI operands. But
the related code has changed a lot in this merge window, so I perfer to
do this in the future, after all below be merged:
git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
kvm-arm64/el2-obj-v4.1
git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
kvm-arm64/pre-nv-5.9
git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/tlbi
Currently, keep the range ops get the level in the addr argument, the classic
ops added the level in the __tlbi_level macro.
>> @@ -108,6 +119,49 @@
>> __tlbi_level(op, (arg | USER_ASID_FLAG), level);\
>> } while (0)
>>
>> +#define __tlbi_last_level(op1, op2, arg, last_level, tlb_level) do {
>> \
>> +if (last_level) { \
>> +__tlbi_level(op1, arg, tlb_level); \
>> +__tlbi_user_level(op1, arg, tlb_level); \
>> +} else {\
>> +__tlbi_level(op2, arg, tlb_level); \
>> +__tlbi_user_level(op2, arg, tlb_level); \
>> +}
Re: [PATCH v1 2/2] arm64: tlb: Use the TLBI RANGE feature in arm64
On Thu, Jul 09, 2020 at 05:10:54PM +0800, Zhenyu Ye wrote:
> Add __TLBI_VADDR_RANGE macro and rewrite __flush_tlb_range().
>
> Signed-off-by: Zhenyu Ye
> ---
> arch/arm64/include/asm/tlbflush.h | 156 --
> 1 file changed, 126 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm64/include/asm/tlbflush.h
> b/arch/arm64/include/asm/tlbflush.h
> index 39aed2efd21b..30e52eae973b 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -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.
> *
> @@ -73,29 +98,15 @@
> * in asm/stage2_pgtable.h.
> */
> #define TLBI_TTL_MASKGENMASK_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) && \
> + !cpus_have_const_cap(ARM64_HAS_TLBI_RANGE) && \
> 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); \
> } \
I think checking for !ARM64_HAS_TLBI_RANGE here is incorrect. I can see
why you attempted this since the range and classic ops have a different
position for the level but now you are not passing the TTL at all for
the classic TLBI. It's also inconsistent to have the range ops get the
level in the addr argument while the classic ops added in the
__tlbi_level macro.
I'd rather have two sets of macros, __tlbi_level and __tlbi_range_level,
called depending on whether you use classic or range ops.
> @@ -108,6 +119,49 @@
> __tlbi_level(op, (arg | USER_ASID_FLAG), level);\
> } while (0)
>
> +#define __tlbi_last_level(op1, op2, arg, last_level, tlb_level) do { \
> + if (last_level) { \
> + __tlbi_level(op1, arg, tlb_level); \
> + __tlbi_user_level(op1, arg, tlb_level); \
> + } else {\
> + __tlbi_level(op2, arg, tlb_level); \
> + __tlbi_user_level(op2, arg, tlb_level); \
> + } \
> +} while (0)
And you could drop this altogether. I know it's slightly more lines of
code but keeping it expanded in __flush_tlb_range() would be clearer.
> +
> +/*
> + * This macro creates a properly formatted VA operand for the TLBI RANGE.
> + * The value bit assignments are:
> + *
> + * +--+--+---+---+---+--+
> + * | ASID | TG | SCALE | NUM | TTL |BADDR |
> + *
Re: [PATCH v1 2/2] arm64: tlb: Use the TLBI RANGE feature in arm64
On 2020/7/9 17:10, Zhenyu Ye wrote: > + /* > + * When cpu does not support TLBI RANGE feature, we flush the tlb > + * entries one by one at the granularity of 'stride'. > + * When cpu supports the TLBI RANGE feature, then: > + * 1. If pages is odd, flush the first page through non-RANGE > + *instruction; > + * 2. For remaining pages: 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': > + * > + * When scale = 3, we can flush no pages because the minumum > + * range is 2^(5*3 + 1) = 0x1. > + * When scale = 2, the minimum range is 2^(5*2 + 1) = 0x800, we can > + * flush 0xe800 pages this time, the num = 0xe800/0x800 - 1 = 0x1c. > + * Remain pages is 0x1a; > + * When scale = 1, the minimum range is 2^(5*1 + 1) = 0x40, no page > + * can be flushed. > + * When 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. > + */ The comments may be too long, probably should be moved to commit messages. Thanks, Zhenyu
