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Re: [Xen-devel] [PATCH v3 2/3] xen/x86: add dom0 memory sizing variants


  • To: Jan Beulich <JBeulich@xxxxxxxx>
  • From: Juergen Gross <jgross@xxxxxxxx>
  • Date: Mon, 10 Dec 2018 15:52:52 +0100
  • Autocrypt: addr=jgross@xxxxxxxx; prefer-encrypt=mutual; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNHkp1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmRlPsLAeQQTAQIAIwUCU4xw6wIbAwcL CQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJELDendYovxMvi4UH/Ri+OXlObzqMANruTd4N zmVBAZgx1VW6jLc8JZjQuJPSsd/a+bNr3BZeLV6lu4Pf1Yl2Log129EX1KWYiFFvPbIiq5M5 kOXTO8Eas4CaScCvAZ9jCMQCgK3pFqYgirwTgfwnPtxFxO/F3ZcS8jovza5khkSKL9JGq8Nk czDTruQ/oy0WUHdUr9uwEfiD9yPFOGqp4S6cISuzBMvaAiC5YGdUGXuPZKXLpnGSjkZswUzY d9BVSitRL5ldsQCg6GhDoEAeIhUC4SQnT9SOWkoDOSFRXZ+7+WIBGLiWMd+yKDdRG5RyP/8f 3tgGiB6cyuYfPDRGsELGjUaTUq3H2xZgIPfOwE0EU4xwFgEIAMsx+gDjgzAY4H1hPVXgoLK8 B93sTQFN9oC6tsb46VpxyLPfJ3T1A6Z6MVkLoCejKTJ3K9MUsBZhxIJ0hIyvzwI6aYJsnOew cCiCN7FeKJ/oA1RSUemPGUcIJwQuZlTOiY0OcQ5PFkV5YxMUX1F/aTYXROXgTmSaw0aC1Jpo w7Ss1mg4SIP/tR88/d1+HwkJDVW1RSxC1PWzGizwRv8eauImGdpNnseneO2BNWRXTJumAWDD pYxpGSsGHXuZXTPZqOOZpsHtInFyi5KRHSFyk2Xigzvh3b9WqhbgHHHE4PUVw0I5sIQt8hJq 5nH5dPqz4ITtCL9zjiJsExHuHKN3NZsAEQEAAcLAXwQYAQIACQUCU4xwFgIbDAAKCRCw3p3W KL8TL0P4B/9YWver5uD/y/m0KScK2f3Z3mXJhME23vGBbMNlfwbr+meDMrJZ950CuWWnQ+d+ Ahe0w1X7e3wuLVODzjcReQ/v7b4JD3wwHxe+88tgB9byc0NXzlPJWBaWV01yB2/uefVKryAf AHYEd0gCRhx7eESgNBe3+YqWAQawunMlycsqKa09dBDL1PFRosF708ic9346GLHRc6Vj5SRA UTHnQqLetIOXZm3a2eQ1gpQK9MmruO86Vo93p39bS1mqnLLspVrL4rhoyhsOyh0Hd28QCzpJ wKeHTd0MAWAirmewHXWPco8p1Wg+V+5xfZzuQY0f4tQxvOpXpt4gQ1817GQ5/Ed/wsDtBBgB CAAgFiEEhRJncuj2BJSl0Jf3sN6d1ii/Ey8FAlrd8NACGwIAgQkQsN6d1ii/Ey92IAQZFggA HRYhBFMtsHpB9jjzHji4HoBcYbtP2GO+BQJa3fDQAAoJEIBcYbtP2GO+TYsA/30H/0V6cr/W V+J/FCayg6uNtm3MJLo4rE+o4sdpjjsGAQCooqffpgA+luTT13YZNV62hAnCLKXH9n3+ZAgJ RtAyDWk1B/0SMDVs1wxufMkKC3Q/1D3BYIvBlrTVKdBYXPxngcRoqV2J77lscEvkLNUGsu/z W2pf7+P3mWWlrPMJdlbax00vevyBeqtqNKjHstHatgMZ2W0CFC4hJ3YEetuRBURYPiGzuJXU pAd7a7BdsqWC4o+GTm5tnGrCyD+4gfDSpkOT53S/GNO07YkPkm/8J4OBoFfgSaCnQ1izwgJQ jIpcG2fPCI2/hxf2oqXPYbKr1v4Z1wthmoyUgGN0LPTIm+B5vdY82wI5qe9uN6UOGyTH2B3p hRQUWqCwu2sqkI3LLbTdrnyDZaixT2T0f4tyF5Lfs+Ha8xVMhIyzNb1byDI5FKCb
  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
  • Delivery-date: Mon, 10 Dec 2018 14:52:58 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 10/12/2018 15:45, Jan Beulich wrote:
>>>> On 10.12.18 at 12:44, <jgross@xxxxxxxx> wrote:
>> Today the memory size of dom0 can be specified only in terms of bytes
>> (either an absolute value or "host-mem - value"). When dom0 shouldn't
>> be auto-ballooned this requires nearly always a manual adaption of the
>> Xen boot parameters to reflect the actual host memory size.
>>
>> Add more possibilities to specify memory sizes. Today we have:
>>
>> dom0_mem= List of ( min:<size> | max:<size> | <size> )
>>
>> with <size> being a positive or negative size value (e.g. 1G).
>>
>> Modify that to:
>>
>> dom0_mem= List of ( min:<sz> | max:<sz> | <sz> )
>> <sz>: <size> | [<size>+]<frac>%
>> <frac>: integer value < 100
>>
>> With the following semantics:
>>
>> <frac>% specifies a fraction of host memory size in percent.
>> <sz> is a percentage of host memory plus an offset.
>>
>> So <sz> being 1G+25% on a 256G host would result in 65G.
>>
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> 
> Once again
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> yet once again with a remark:
> 
>> -static long __init parse_amt(const char *s, const char **ps)
>> +static int __init parse_amt(const char *s, const char **ps, struct memsize 
>> *sz)
>>  {
>> -    long pages = parse_size_and_unit((*s == '-') ? s+1 : s, ps) >> 
>> PAGE_SHIFT;
>> -    return (*s == '-') ? -pages : pages;
>> +    unsigned long val;
>> +    struct memsize tmp = { };
>> +    unsigned int items = 0;
>> +
>> +    tmp.minus = (*s == '-');
>> +    if ( tmp.minus )
>> +        s++;
>> +
>> +    do
>> +    {
>> +        if ( !isdigit(*s) )
>> +            return -EINVAL;
>> +
>> +        val = parse_size_and_unit(s, ps);
>> +        s = *ps;
>> +        if ( *s == '%' )
>> +        {
>> +            if ( val >= 100 )
>> +                return -EINVAL;
>> +            tmp.percent = val;
>> +            s++;
>> +            items++; /* No other item allowed. */
> 
> Isn't this unnecessary with ...
> 
>> +        }
>> +        else
>> +        {
>> +            /* <size> item must be first one. */
>> +            if ( items )
>> +                return -EINVAL;
>> +            tmp.nr_pages = val >> PAGE_SHIFT;
>> +        }
>> +        items++;
> 
> ... this? However, allowing <frac>%+<size> would apparently have
> been easy (and add further flexibility).

That would require two booleans instead. Otherwise <frac>%+<frac>%
wouldn't be rejected. In case anyone else thinks this would be better
I can change it, of course.


Juergen

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