[bug #42944] TFTP: "error: timeout reading '/rhel60x64/vmlinuz'" on hyper-v Generation 2 VMs with UEFI and secure boot disabled

[Rigoberto Corujo]

Follow-up Comment #1, bug #42944 (project grub):

I had sent email to address@hidden on September 28th 2014 root causing the
problem.  Below is a copy of the email:

=====================================

Hi,
 
When using the Hyper-V Generation 2 hypervisor and trying to PXE boot a VM
guest, the GRUB2 time functions are not working, which causes the PXE menu to
display for a fraction of a second, instead of the usual 10 seconds or so,
then boot the default menu entry, and immediately report that it timed out
while loading the kernel.  In other words, the time goes by superfast.  For
example, you'll get the message:
 
error: time out opening `rhel60x64/vmlinuz'.
 
This is because the functions in "./grub-core/kern/i386/tsc.c" that are used
to calculate time are not working.
 
I found this site, which seems to say that the devices that GRUB2 uses to
calculate the time have been removed from Hyper-V Generation 2:
 
Hyper-V generation 2 virtual machines – part 1 - John Howard - Senior
Program Manager in the Hyper-V team at Microsoft - Site Home - TechNet Blogs
 
Referring to changes made to Hyper-V Generation 2, it says:
Then we changed other devices such as removing the legacy i8042 keyboard
controller (which has an interesting side effect I will talk about in a future
part), PS/2 mouse, S3 Video, the Programmable Interrupt Controller (PIC), the
Programmable Interrupt Timer (PIT), the Super I/O device on which floppy
support relied. We actually went even further by removing the PCI bus as well.
For good measure, we also removed the speaker and the numerical co-processor.
We also revised ACPI.
I noticed that in "tsc.c", the grub_inb(GRUB_PIT_SPEAKER_PORT) call always
returns 0xff on Hyper-V Generation 2.
 
static void
grub_pit_wait (grub_uint16_t tics)
{
...
  grub_outb (grub_inb (GRUB_PIT_SPEAKER_PORT)
             & ~ (GRUB_PIT_SPK_DATA | GRUB_PIT_SPK_TMR2),
             GRUB_PIT_SPEAKER_PORT);
...
}
 
Is this a known issue that is already being addressed?
 
Thank you,
 
Rigoberto Corujo


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