From: Lulu Cheng <chenglulu@loongson.cn>
To: Xi Ruoyao <xry111@xry111.site>,
gcc-patches@gcc.gnu.org, pinskia@gcc.gnu.org,
richard.sandiford@arm.com
Cc: i@xen0n.name, xuchenghua@loongson.cn
Subject: Re: [PATCH] LoongArch: Change the value of macro TRY_EMPTY_VM_SPACE from 0x8000000000 to 0x1000000000.
Date: Tue, 21 Feb 2023 21:03:03 +0800 [thread overview]
Message-ID: <b110118d-84f2-030c-c6ce-58c5b682076f@loongson.cn> (raw)
In-Reply-To: <ca044965aa9b8b8a25818583f05302d1de47abe3.camel@xry111.site>
在 2023/2/21 下午3:41, Xi Ruoyao 写道:
> On Tue, 2023-02-21 at 15:20 +0800, Lulu Cheng wrote:
>> Like la264 only has 40 effective bits of virtual address space.
> I'm OK with the change. But the VA length is configurable building the
> kernel. Is there any specific reason LA264 has to use the 40-bit
> configuration, or should we reword the commit message like "for
> supporting the configuration with less page table level or smaller page
> size"?
I consulted with my colleagues who are working on the kernel,
it looks like this:
The la264 chip desgn is physically 40-bit virtual address.
User mode and kernel mode each account for half:
User mode : 0x0-0x7f ffff ffff
Kernel mode: 0xffff ff80 0000 0000 -0xffff ffff ffff ffff
The high bit is the sign extension of bit39.
>
>> When TRY_EMPTY_VM_SPACE is set to 0x8000000000, it just exceeds
>> the range of 40-bit virtual address, causing the mmap mapping
>> to fail, thus causing the pch function to fail. To be compatible
>> with this situation set the macro to 0x1000000000.
>>
>> gcc/ChangeLog:
>>
>> * config/host-linux.cc (TRY_EMPTY_VM_SPACE): Modify the value
>> of
>> the macro to 0x1000000000.
>> ---
>> gcc/config/host-linux.cc | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gcc/config/host-linux.cc b/gcc/config/host-linux.cc
>> index a891651a7b6..d1aa7ab28ca 100644
>> --- a/gcc/config/host-linux.cc
>> +++ b/gcc/config/host-linux.cc
>> @@ -99,7 +99,7 @@
>> #elif defined(__riscv) && defined (__LP64__)
>> # define TRY_EMPTY_VM_SPACE 0x1000000000
>> #elif defined(__loongarch__) && defined(__LP64__)
>> -# define TRY_EMPTY_VM_SPACE 0x8000000000
>> +# define TRY_EMPTY_VM_SPACE 0x1000000000
>> #else
>> # define TRY_EMPTY_VM_SPACE 0
>> #endif
next prev parent reply other threads:[~2023-02-21 13:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-21 7:20 Lulu Cheng
2023-02-21 7:41 ` Xi Ruoyao
2023-02-21 13:03 ` Lulu Cheng [this message]
2023-02-21 13:56 ` WANG Xuerui
2023-02-22 9:30 ` Lulu Cheng
2023-02-22 9:35 ` WANG Xuerui
2023-02-22 9:49 ` Lulu Cheng
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