linux-kernel - Re: [PATCH v2 2/2] RISC-V: Don't use a global include guard for uapi/asm/syscalls.h

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Message-ID: <mhng-ef018453-7a99-48b3-bda5-5408383d9566@palmer-si-x1c4>
Date:   Thu, 09 Aug 2018 20:59:59 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     linux@...ck-us.net
CC:     Christoph Hellwig <hch@...radead.org>, aou@...s.berkeley.edu,
        Arnd Bergmann <arnd@...db.de>, tklauser@...tanz.ch,
        Andrew Waterman <andrew@...ive.com>, dan.carpenter@...cle.com,
        linux@...inikbrodowski.net, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, marcus@...pp.se
Subject:     Re: [PATCH v2 2/2] RISC-V: Don't use a global include guard for uapi/asm/syscalls.h

On Thu, 09 Aug 2018 19:40:55 PDT (-0700), linux@...ck-us.net wrote:
> On 08/09/2018 06:03 PM, Palmer Dabbelt wrote:
>> On Thu, 09 Aug 2018 14:24:22 PDT (-0700), linux@...ck-us.net wrote:
>>> On Thu, Aug 09, 2018 at 01:25:24PM -0700, Palmer Dabbelt wrote:
>>>> This file is expected to be included multiple times in the same file in
>>>> order to allow the __SYSCALL macro to generate system call tables.  With
>>>> a global include guard we end up missing __NR_riscv_flush_icache in the
>>>> syscall table, which results in icache flushes that escape the vDSO call
>>>> to not actually do anything.
>>>>
>>>> The fix is to move to per-#define include guards, which allows the
>>>> system call tables to actually be populated.  Thanks to Macrus Comstedt
>>>> for finding and fixing the bug!
>>>>
>>>> I also went ahead and fixed the SPDX header to use a //-style comment,
>>>> which I've been told is the canonical way to do it.
>>>>
>>>> Cc: Marcus Comstedt <marcus@...pp.se>
>>>> Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
>>>
>>> [Compile-]Tested-by: Guenter Roeck <linux@...ck-us.net>
>>>
>>> on top of linux-next after reverting the version of the patch there.
>>>
>>> I also tried to run the resulting image (defconfig) with qemu (built
>>> from https://github.com/riscv/riscv-qemu.git), but that still doesn't
>>> work. I assume there are still some patches missing ?
>>
>> Do you have the PLIC patches?  They'll be necessary to make this all work, and there's a v4 out now that when combined with for-next should get you to userspace.
>>
>>     https://lore.kernel.org/lkml/20180809075602.989-1-hch@lst.de/T/#u
>>
> Yes, after merging that branch on top of linux-next I can boot into Linux.
> If I add my "riscv: Drop setup_initrd" patch as well, I can boot using
> initrd, otherwise I have to use virtio-blk-device.

Awesome!  If you patch isn't on for-next then I must have missed it, do you 
mind sending me a pointer?  I can't find any references in my email.

>> Also, what is your methodology?  I follow
>>
>>     https://wiki.qemu.org/Documentation/Platforms/RISCV
>>
>> and could could natively compile and run hello world with an earlier version of Christoph's patch set, which is really only cosmetically different than the v4. I use qemu's master branch as well, which when I tried was exactly 3.0.0-rc3.
>>
>
> That doesn't work for me, possibly because I don't specify a bbl
> image with -kernel but vmlinux (using -bios for the bbl image).
> I use branch qemu-for-upstream of https://github.com/riscv/riscv-qemu.git.
>
> Guenter