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Date: Wed, 24 Jan 2018 22:20:57 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20180124221602-mutt-send-email-mst@kernel.org>
References: <20180117081325.11924-1-haozhong.zhang@intel.com>
	<20180117081325.11924-2-haozhong.zhang@intel.com>
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In-Reply-To: <20180117081325.11924-2-haozhong.zhang@intel.com>
Subject: Re: [Qemu-devel] [PATCH v3 1/3] util/mmap-alloc: support MAP_SYNC
 in qemu_ram_mmap()
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To: Haozhong Zhang <haozhong.zhang@intel.com>
Cc: qemu-devel@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>, Igor Mammedov <imammedo@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, dgilbert@redhat.com, Xiao Guangrong <xiaoguangrong.eric@gmail.com>, Stefan Hajnoczi <stefanha@redhat.com>, Dan Williams <dan.j.williams@intel.com>

> index 50385e3f81..dd5876471f 100644
> --- a/include/qemu/mmap-alloc.h
> +++ b/include/qemu/mmap-alloc.h
> @@ -7,7 +7,8 @@ size_t qemu_fd_getpagesize(int fd);
>  
>  size_t qemu_mempath_getpagesize(const char *mem_path);
>  
> -void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared);
> +void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared,
> +                    OnOffAuto sync);
>  
>  void qemu_ram_munmap(void *ptr, size_t size);
>  

And Marcel plans to add a remappable flag ...  Is it time we
switched to a flags field?

> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index adb3758275..0ff10cb529 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -372,6 +372,24 @@ void qemu_anon_ram_free(void *ptr, size_t size);
>  #  define QEMU_VMALLOC_ALIGN getpagesize()
>  #endif
>  
> +/*
> + * MAP_SHARED_VALIDATE and MAP_SYNC were introduced in Linux kernel
> + * 4.15, so they may not be defined when compiling on older kernels.
> + */
> +#ifdef CONFIG_LINUX
> +#ifndef MAP_SHARED_VALIDATE
> +#define MAP_SHARED_VALIDATE   0x3
> +#endif
> +#ifndef MAP_SYNC
> +#define MAP_SYNC              0x80000
> +#endif
> +#define QEMU_HAS_MAP_SYNC     true
> +#else  /* !CONFIG_LINUX */
> +#define MAP_SHARED_VALIDATE   0x0
> +#define MAP_SYNC              0x0
> +#define QEMU_HAS_MAP_SYNC     false
> +#endif /* CONFIG_LINUX */
> +
>  #ifdef CONFIG_POSIX
>  struct qemu_signalfd_siginfo {
>      uint32_t ssi_signo;   /* Signal number */

Please just import this into standard-headers from Linux.