Re: [Xen-devel] [PATCH] libxc: lzma build fix

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Fri, 2011-01-28 at 18:51 +0000, Ian Jackson wrote: 
> Ian Jackson writes ("Re: [Xen-devel] [PATCH] libxc: lzma build fix"):
> > Yes, we could revert this patch and hardcode a value.  32M seems
> > plausible.
> 
> How about this.
> 
> Ian.
> 
> 
> libxc: Do not use host physmem as parameter to lzma decoder

Strictly speaking it's the dom0 physmem.

> It's not clear why a userspace lzma decode would want to use that
> particular value, what bearing it has on anything or why it would
> assume it could use 1/3 of the total RAM in the system (potentially
> quite a large amount of RAM) as opposed to any other limit number.

Sounds good to me ;-)

> Instead, hardcode 32Mby.
> 
> This reverts 22830:c80960244942, removes the xc_get_physmem/physmem
> function entirely, and replaces the expression at the call site with a
> fixed constant.
> 
> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Acked-by: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>

> Cc: Christoph Egger <Christoph.Egger@xxxxxxx>
> 
> diff -r 88cf07fed7d2 tools/libxc/xc_dom_bzimageloader.c
> --- a/tools/libxc/xc_dom_bzimageloader.c      Fri Jan 28 18:39:09 2011 +0000
> +++ b/tools/libxc/xc_dom_bzimageloader.c      Fri Jan 28 18:49:08 2011 +0000
> @@ -152,7 +152,7 @@ static int xc_try_lzma_decode(
>      int outsize;
>      const char *msg;
>  
> -    ret = lzma_alone_decoder(&stream, xc_get_physmem() / 3);
> +    ret = lzma_alone_decoder(&stream, 32*1024*1024);
>      if ( ret != LZMA_OK )
>      {
>          DOMPRINTF("LZMA: Failed to init stream decoder");
> diff -r 88cf07fed7d2 tools/libxc/xc_linux.c
> --- a/tools/libxc/xc_linux.c  Fri Jan 28 18:39:09 2011 +0000
> +++ b/tools/libxc/xc_linux.c  Fri Jan 28 18:49:08 2011 +0000
> @@ -55,27 +55,6 @@ void discard_file_cache(xc_interface *xc
>      errno = saved_errno;
>  }
>  
> -uint64_t xc_get_physmem(void)
> -{
> -    uint64_t ret = 0;
> -    const long pagesize = sysconf(_SC_PAGESIZE);
> -    const long pages = sysconf(_SC_PHYS_PAGES);
> -
> -    if ( (pagesize != -1) || (pages != -1) )
> -    {
> -        /*
> -         * According to docs, pagesize * pages can overflow.
> -         * Simple case is 32-bit box with 4 GiB or more RAM,
> -         * which may report exactly 4 GiB of RAM, and "long"
> -         * being 32-bit will overflow. Casting to uint64_t
> -         * hopefully avoids overflows in the near future.
> -         */
> -        ret = (uint64_t)(pagesize) * (uint64_t)(pages);
> -    }
> -
> -    return ret;
> -}
> -
>  /*
>   * Local variables:
>   * mode: C
> diff -r 88cf07fed7d2 tools/libxc/xc_netbsd.c
> --- a/tools/libxc/xc_netbsd.c Fri Jan 28 18:39:09 2011 +0000
> +++ b/tools/libxc/xc_netbsd.c Fri Jan 28 18:49:08 2011 +0000
> @@ -23,9 +23,6 @@
>  #include <xen/sys/evtchn.h>
>  #include <unistd.h>
>  #include <fcntl.h>
> -#include <stdio.h>
> -#include <errno.h>
> -#include <sys/sysctl.h>
>  
>  static xc_osdep_handle netbsd_privcmd_open(xc_interface *xch)
>  {
> @@ -354,24 +351,6 @@ void discard_file_cache(xc_interface *xc
>      errno = saved_errno;
>  }
>  
> -uint64_t xc_get_physmem(void)
> -{
> -    int mib[2], rc;
> -    size_t len;
> -    uint64_t physmem;
> -
> -    mib[0] = CTL_HW;
> -    mib[1] = HW_PHYSMEM64;
> -    rc = sysctl(mib, 2, &physmem, &len, NULL, 0);
> -
> -    if (rc == -1) {
> -        /* PERROR("%s: Failed to get hw.physmem64: %s\n", strerror(errno)); 
> */
> -        return 0;
> -    }
> -
> -    return physmem;
> -}
> -
>  static struct xc_osdep_ops *netbsd_osdep_init(xc_interface *xch, enum 
> xc_osdep_type type)
>  {
>      switch ( type )
> diff -r 88cf07fed7d2 tools/libxc/xc_private.h
> --- a/tools/libxc/xc_private.h        Fri Jan 28 18:39:09 2011 +0000
> +++ b/tools/libxc/xc_private.h        Fri Jan 28 18:49:08 2011 +0000
> @@ -275,9 +275,6 @@ void bitmap_byte_to_64(uint64_t *lp, con
>  /* Optionally flush file to disk and discard page cache */
>  void discard_file_cache(xc_interface *xch, int fd, int flush);
>  
> -/* How much physical RAM is available? */
> -uint64_t xc_get_physmem(void);
> -
>  #define MAX_MMU_UPDATES 1024
>  struct xc_mmu {
>      mmu_update_t updates[MAX_MMU_UPDATES];



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