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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Sun, 7 Feb 2021 22:51:08 +0100
Message-ID: <CAK8P3a13aGbqvTxL+5OQxu-wPa6RDHQJkJ_n8O6YeOibbJQ2yg@mail.gmail.com>
Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin
To:     Zhou Wang <wangzhou1@hisilicon.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux API <linux-api@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        gregkh <gregkh@linuxfoundation.org>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Jason Gunthorpe <jgg@ziepe.ca>, kevin.tian@intel.com,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Eric Auger <eric.auger@redhat.com>,
        "Liguozhu (Kenneth)" <liguozhu@hisilicon.com>,
        Zhangfei Gao <zhangfei.gao@linaro.org>,
        Sihang Chen <chensihang1@hisilicon.com>
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On Sun, Feb 7, 2021 at 9:18 AM Zhou Wang <wangzhou1@hisilicon.com> wrote:

> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index cccfbbe..3f49529 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -891,6 +891,8 @@ __SYSCALL(__NR_faccessat2, sys_faccessat2)
>  __SYSCALL(__NR_process_madvise, sys_process_madvise)
>  #define __NR_epoll_pwait2 441
>  __SYSCALL(__NR_epoll_pwait2, compat_sys_epoll_pwait2)
> +#define __NR_mempinfd 442
> +__SYSCALL(__NR_mempinfd, sys_mempinfd)

This adds a compat syscall for 32-bit tasks running on arm64 without adding
the same for the native arch/arm syscall table. Those two need to always
stay synchronized. In fact, new system call should ideally get assigned
on all architectures at the same time, with the same number (or +110
on arch/alpha).

         Arnd