Re: [Xen-devel] [PATCH 3/3] xen-init-dom0: set Dom0 UUID if requested

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Nov 15, 2018 at 11:20:37AM +0000, Wei Liu wrote:
> On Thu, Nov 15, 2018 at 10:45:52AM +0000, Edwin Török wrote:
> > On 14/11/2018 18:17, Wei Liu wrote:
> > > Read from XEN_CONFIG_DIR/dom0-uuid. If it contains a valid UUID, set
> > > it for Dom0.
> > > 
> > > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > 
> > [snip]
> > In general this looks good, however I am not familiar with libxl
> > conventions, so just some generic comments below.
> > 
> > > +static void get_dom0_uuid(libxl_uuid *uuid)
> > > +{
> > > +    int fd = -1;
> > > +    ssize_t r;
> > > +    char uuid_buf[LIBXL_UUID_FMTLEN+1];
> > > +
> > > +    libxl_uuid_clear(uuid);
> > > +
> > > +    fd = open(DOM0_UUID_PATH, O_RDONLY);
> > > +    if (fd < 0) {
> > > +        fprintf(stderr, "failed to open %s\n", DOM0_UUID_PATH);
> > > +        goto out;
> > > +    }
> > > +
> > > +    r = read(fd, uuid_buf, LIBXL_UUID_FMTLEN);
> > 
> > Could this be a short read? I'm not familiar with libxl conventions, but
> > would there be a utility function that repeats the read if it is short,
> > or would fread be better?
> 
> I can use libxl_read_exactly instead. That saves me from writing some
> code to handle every corner case.
> 

On second thought, this requires code to allocating and destroying libxl
ctx. I will write a loop here to handle short-read instead.

Wei.

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