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Re: [qemu-s390x] Interactive Boot Menu: New Fields in IPLB
From: |
Cornelia Huck |
Subject: |
Re: [qemu-s390x] Interactive Boot Menu: New Fields in IPLB |
Date: |
Fri, 8 Dec 2017 11:19:19 +0100 |
On Thu, 7 Dec 2017 18:56:16 -0500
"Collin L. Walling" <address@hidden> wrote:
> --- The Fields We Need To Store ---
>
> Currently, we're utilizing 3 bytes out of a 77 byte reserved field in
> the IPLB for
> CCW and SCSI. We do this because need a way to pass the Qemu command
> line options
> for a boot menu (on/off and timeout) to the s390-ccw bios. We require
> only two
> fields in the IPLB, totaling 3 bytes:
Hm, are we actually that constrained with space?
>
> * uint8_t boot_menu_flag
> o determines if we should show the menu or not
Should be fine. I'd recommend something along the lines of
- bit 0: show a boot menu
- bit 1-7: reserved [for future use]
>
> * uint16_t boot_menu_timeout
> o stored as milliseconds
> o A max value of approx 65,000 gives us 65 seconds -- should be
> plenty
65 seconds should be enough for everyone?
:)
> o could potentially be reduced to one byte, and we store the value
> as seconds instead
As said, do we really need to worry about the space this is using up
here?
>
> Note: these fields *only*have value in a QEMU environment.