Bug 1120017
Summary: | Qemu should give a warning when using boot=off to boot a guest with only one disk | ||
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Product: | Red Hat Enterprise Linux 6 | Reporter: | Chengyou Liu <cheliu> |
Component: | qemu-kvm | Assignee: | Kevin Wolf <kwolf> |
Status: | CLOSED NOTABUG | QA Contact: | Virtualization Bugs <virt-bugs> |
Severity: | medium | Docs Contact: | |
Priority: | unspecified | ||
Version: | 6.6 | CC: | acathrow, bsarathy, chayang, coli, juzhang, kwolf, michen, mkenneth, qzhang, shuang, virt-maint |
Target Milestone: | rc | ||
Target Release: | --- | ||
Hardware: | Unspecified | ||
OS: | Unspecified | ||
Whiteboard: | |||
Fixed In Version: | Doc Type: | Bug Fix | |
Doc Text: | Story Points: | --- | |
Clone Of: | Environment: | ||
Last Closed: | 2014-07-22 12:20:59 UTC | Type: | Bug |
Regression: | --- | Mount Type: | --- |
Documentation: | --- | CRM: | |
Verified Versions: | Category: | --- | |
oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
Cloudforms Team: | --- | Target Upstream Version: | |
Embargoed: |
Description
Chengyou Liu
2014-07-16 05:15:00 UTC
Boot a guest with option "-drive boot=off" (but there is no warning). The guest can boot normally w/ the option. QEMU 0.12.1 monitor - type 'help' for more information (qemu) info status VM status: running The warning from (upstream qemu based) RHEL 7 would be wrong here because (qemu-kvm based) RHEL 6 implements boot=on and doesn't ignore it. The default is boot=off and it behaves like RHEL 7. The BIOS need to have its own disk driver that can access the disk - this was only true for IDE in the RHEL 5 and early RHEL 6 days. boot=on enables extboot, which adds a ROM to the guest that can bypass the emulated device and directly access the qemu block driver, so that the BIOS doesn't need a disk driver (this was used for virtio-blk and SCSI). These days, SeaBIOS has native support for (amongst others) virtio-blk and SCSI, so this is not required any more for booting from such devices. Essentially, extboot hasn't only disappeared, but also become completely useless because the same functionality is provided by SeaBIOS now. |