Old kernels that used high memory only allowed the initrd to be in the
first 896MB of memory. If you load the initrd above, they complain
that "initrd extends beyond end of memory".
In order to fix this, while not breaking machines with small amounts
of memory fixed by cdebec5 (linuxboot: compute initrd loading address,
2014-10-06), we need to distinguish two cases. If pc.c placed the
initrd at end of memory, use the new algorithm based on the e801
memory map. If instead pc.c placed the initrd at the maximum address
specified by the bzImage, leave it there.
The only interesting part is that the low-memory info block is now
loaded very early, in real mode, and thus the 32-bit address has
to be converted into a real mode segment. The initrd address is
also patched in the info block before entering real mode, it is
simpler that way.
This fixes booting the RHEL4.8 32-bit installation image with 1GB
of RAM.
Cc: qemu-stable@nongnu.org
Cc: mst@redhat.com
Cc: jsnow@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Even though hw/i386/pc.c tries to compute a valid loading address for the
initrd, close to the top of RAM, this does not take into account other
data that is malloced into that memory by SeaBIOS.
Luckily we can easily look at the memory map to find out how much memory is
used up there. This patch places the initrd in the first four gigabytes,
below the first hole (as returned by INT 15h, AX=e801h).
Without this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x0710a000-0x07fd7fff]
With this patch:
[ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff]
[ 0.000000] RAMDISK: [mem 0x07112000-0x07fdffff]
So linuxboot is able to use the 64k that were added as padding for
QEMU <= 2.1.
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Currently linuxboot.bin and multiboot.bin option roms override int19
vector to intercept boot process. No sane option rom should do that.
Provide bev entry instead that will be called by BIOS if option rom
is selected for booting.
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Commit dd4239d657 broke multiboot. It replaced the
instruction "rep insb (%dx), %es:(%edi)" by the binary output of
"addr32 rep insb (%dx), %es:(%di)".
Linuxboot calls the respective helper function in a code16 section. So the
original instruction was automatically translated to its "addr32" equivalent.
For multiboot, we're running in code32 so gcc didn't add the "addr32" which
breaks the instruction.
This patch splits that helper function in one which uses addr32 and one which
does not, so everyone's happy.
The good news is that nobody probably cared so far. The bundled multiboot.bin
binary was built before the change and is thus correct.
Please also put this patch into -stable.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
The gdt address calculation in linuxboot.bin is broken in two ways: first
it loads %cs into %eax, but that instruction leaves the high bits of %eax
undefined and we did not clear them. Secondly, we completely ignore the
incorrect %eax, and use the undefined %ebx instead.
With these issues fixed, linuxboot works again.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
The %gs segment that was used was not matching the comments.
I just moved the GDT descriptor on the stack instead.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
While trying to run -kernel with -bios pc-bios/pcbios.bin, I realized
that I was actually writing data to %es, but only set up %ds to a 32-bit
segment we want to write to.
So at the end of the day the data hasn't actually been copied. Oops.
So here's a fix to set ES instead of DS, which makes -kernel work with
BOCHS bios again (and actually makes the code do the correct thing)!
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
We already have a working multiboot implementation that uses fw_cfg to get
its kernel module etc. data in int19 runtime now.
So what's missing is a working linux boot option rom. While at it I figured it
would be a good idea to take the opcode generator out of pc.c and instead use
a proper option rom, like we do with multiboot.
So here it is - an fw_cfg using option rom for -kernel with linux!
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Paolo Bonzini
Gleb Natapov
Alexander Graf
Avi Kivity