Re: [PATCH v5 6/9] libxc: create unmapped initrd in domain builder if supported

[Ian Campbell <ian.campbell@citrix.com>]

On Mon, 2015-11-30 at 13:20 +0100, Juergen Gross wrote:
> On 30/11/15 12:23, Ian Campbell wrote:
> > On Mon, 2015-11-30 at 12:03 +0100, Juergen Gross wrote:
> > > On 30/11/15 11:52, Ian Campbell wrote:
> > > > On Mon, 2015-11-30 at 10:51 +0000, Ian Campbell wrote:
> > > > > On Mon, 2015-11-30 at 11:47 +0100, Juergen Gross wrote:
> > > > > > On 30/11/15 11:34, Ian Campbell wrote:
> > > > > > > On Mon, 2015-11-30 at 11:23 +0100, Juergen Gross wrote:
> > > > > > > > On 30/11/15 11:20, Wei Liu wrote:
> > > > > > > > > On Thu, Nov 26, 2015 at 08:35:02AM +0100, Juergen Gross
> > > > > > > > > wrote:
> > > > > > > > > >  
> > > > > > > > > >      /* initrd parameters as specified in start_info
> > > > > > > > > > page
> > > > > > > > > > */
> > > > > > > > > > -    unsigned long initrd_start;
> > > > > > > > > > -    unsigned long initrd_len;
> > > > > > > > > > +    uint64_t initrd_start;
> > > > > > > > > > +    uint64_t initrd_len;
> > > > > > > > > >  
> > > > > > > > > 
> > > > > > > > > I think these should be of type xen_vaddr_t. Doesn't make
> > > > > > > > > a
> > > > > > > > > difference
> > > > > > > > > in the end though.
> > > > > > > > 
> > > > > > > > xen_vaddr_t seems not to be appropriate. It can be either a
> > > > > > > > virtual
> > > > > > > > address or a pfn.
> > > > > > > 
> > > > > > > Did you mean a virtual address or a physical _address_?
> > > > > > > Potentially
> > > > > > > mixing
> > > > > > > addresses and frame numbers in a single variable seems liable
> > > > > > > to
> > > > > > > be
> > > > > > > confusing, at best.
> > > > > > 
> > > > > > No, it's really a pfn. And this is part of the stable interface
> > > > > > between
> > > > > > hypervisor and the pv-domU since more than 5 years now.
> > > > > 
> > > > > Including the virtual address bit?
> > > > > 
> > > > > That's a shame.
> > > > 
> > > > ... and that being the case would you mind adding a comment here
> > > > explaining
> > > > the two forms of these variables and the flag which indicates which
> > > > one
> > > > is
> > > > "in force" at a given moment.
> > > 
> > > The comment in the struct already tells us that initrd_start and
> > > initrd_len are in the very same format as in the start_info page.
> > > Both fields are meant to be opaque to most of the domain builder
> > > parts.
> > > 
> > > The only function dealing with the differences is
> > > xc_dom_build_image()
> > > which already contains the appropriate flag. I added this on your
> > > request. You acked the resulting patch. So why do you want to add
> > > another comment now?
> > 
> > I hadn't realised at the time that the semantics of these fields was
> > so,
> > uh, interesting.
> 
> :-)
> 
> I guess due to the lack of a comment? ;-)

;-)

> Okay, I'll add one when submitting the patch after (hopefully) Boris
> confirmed it is fixing his problem.

Thanks!

FYI attempting to upgrade osstest to use Debian Jessie in the guest seems
to have exposed another issue here.

http://logs.test-lab.xenproject.org/osstest/logs/65172/test-amd64-amd64-amd64-pvgrub/info.html

      Booting 'Debian GNU/Linux, kernel 3.16.0-4-amd64'

    root  (hd0,0)
     Filesystem type is ext2fs, partition type 0x83
    kernel  /boot/vmlinuz-3.16.0-4-amd64 root=UUID=12447529-e85a-4b41-86b6-3e83ccfc
    1377 ro 
    initrd  /boot/initrd.img-3.16.0-4-amd64

    ============= Init TPM Front ================
    Tpmfront:Error Unable to read device/vtpm/0/backend-id during tpmfront initialization! error = ENOENT
    Tpmfront:Info Shutting down tpmfront
    pin_table(x) returned 1357193
    close(3)

    Error 9: Unknown boot failure

    Press any key to continue...

xen.git 6853c9bf9ff0 is OK, whereas 713b7e4ef2aa is not. Adding your two
outstanding patches:
    libxc: correct domain builder for 64 bit guest with 32 bit tools
    libxc: use correct return type for do_memory_op()

Doesn't appear to have helped. Anyway, I was in the process of
investigating/bisecting etc but since I was mailing you any way I thought
I'd mention it. I'll start a fresh thread once I have some more to go on.

Ian.

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