Re: Kernel using LZMA compression
The executive summary is: Xen does not let a kernel boot itself, because mimicking bare hardware is too tedious (and pointless.) Instead, Xen instantiates an instance of a kernel into the Xen environment. To do this instantiation, Xen does its own decompression, so Xen must know everything about the compression. I know you're right. But that sound stupid to me: The kernel itself has routines built-in for decompression. Why isn't it enough to let Xen use the same routines for decompression as the kernel? -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
On 11/04/2009 06:18 PM, Ikem Krueger wrote: The executive summary is: Xen does not let a kernel boot itself, because mimicking bare hardware is too tedious (and pointless.) Instead, Xen instantiates an instance of a kernel into the Xen environment. To do this instantiation, Xen does its own decompression, so Xen must know everything about the compression. I know you're right. But that sound stupid to me: The kernel itself has routines built-in for decompression. Why isn't it enough to let Xen use the same routines for decompression as the kernel? I am reading between the lines here (I have never looked at this stuff in Xen) but I would assume it's for the reason given above. The kernel's own decompression routines must run very early on in the boot process - well before the first line of C code runs and while the CPU (on x86) is still running in legacy real addressing mode (right after the handover from the bootloader and relocation of the kernel image). It's emulating this early-boot environment that is tedious and pointless and being able to use the in-kernel decompresser is not sufficient motivation to go down that route. Regards, Bryn. -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
I am reading between the lines here (I have never looked at this stuff in Xen) but I would assume it's for the reason given above. The kernel's own decompression routines must run very early on in the boot process - well before the first line of C code runs and while the CPU (on x86) is still running in legacy real addressing mode (right after the handover from the bootloader and relocation of the kernel image). Ok. Sounds plausible. How is it to seperate the routines? Can they brought from legacy mode to real mode? -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
On 11/04/2009 06:37 PM, Ikem Krueger wrote: I am reading between the lines here (I have never looked at this stuff in Xen) but I would assume it's for the reason given above. The kernel's own decompression routines must run very early on in the boot process - well before the first line of C code runs and while the CPU (on x86) is still running in legacy real addressing mode (right after the handover from the bootloader and relocation of the kernel image). Ok. Sounds plausible. How is it to seperate the routines? Can they brought from legacy mode to real mode? Quite tricky I'd guess - it's chicken-and-egg. The code to switch the CPU from real mode to protected mode is in the kernel's startup routines *inside* the compressed image. I don't think anyone is going to want to reorganise things to move that code to the primitive early-boot period - the idea is to do as little as possible in that part of the kernel and leave everything else to later in the boot process when life gets easier. Decompressing the kernel is always going to be done in that part of the startup sequence because that's when it has to happen. Regards, Bryn. -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Kernel using LZMA compression
As I know, the kernel is compressed with bzip2 or gzip. How about using LZMA instead? Or is that already the case? -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
On Sat, Oct 31, 2009 at 2:24 PM, Ikem Krueger ikem.krue...@googlemail.com wrote: As I know, the kernel is compressed with bzip2 or gzip. How about using LZMA instead? Or is that already the case? There is such an option but it is currently disabled due to missing support in xen. -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
As I know, the kernel is compressed with bzip2 or gzip. How about using LZMA instead? Or is that already the case? There is such an option but it is currently disabled due to missing support in xen. Thanks. But don't understand. What has LZMA todo with Xen? -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
On Sat, Oct 31, 2009 at 6:03 PM, Ikem Krueger ikem.krue...@googlemail.com wrote: As I know, the kernel is compressed with bzip2 or gzip. How about using LZMA instead? Or is that already the case? There is such an option but it is currently disabled due to missing support in xen. Thanks. But don't understand. What has LZMA todo with Xen? https://bugzilla.redhat.com/show_bug.cgi?id=515831 -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
Re: Kernel using LZMA compression
Thanks. But don't understand. What has LZMA todo with Xen? https://bugzilla.redhat.com/show_bug.cgi?id=515831 The executive summary is: Xen does not let a kernel boot itself, because mimicking bare hardware is too tedious (and pointless.) Instead, Xen instantiates an instance of a kernel into the Xen environment. To do this instantiation, Xen does its own decom- pression, so Xen must know everything about the compression. -- -- fedora-devel-list mailing list fedora-devel-list@redhat.com https://www.redhat.com/mailman/listinfo/fedora-devel-list
