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Bug #12939
closed
avoid packing and bitfields in bhyve VMCB
Start date:
Due date:
% Done:
100%
Estimated time:
Difficulty:
Medium
Tags:
bhyve
Gerrit CR:
External Bug:
Description
The control and state structs for the SVM VMCB in bhyve are defined as packed structs and make heavy use of C bitfields. The former attribute (packed-ness) causes gcc9 to gripe about alignment issues:
../../i86pc/io/vmm/amd/svm.c:1518:49: error: taking address of packed member of 'struct vmcb_state' may result in an unaligned pointer value [-Werror=address-of-packed-member]
1518 | handled = x86_emulate_cpuid(svm_sc->vm, vcpu, &state->rax,
| ^~~~~~~~~~~
The latter (bitfield usage) goes against our style inclinations in illumos.
It would be nice to clean up the struct definitions for both vmcb_ctrl and vmcb_state to address these issues.
Updated by Patrick Mooney almost 3 years ago
In a test compile, tsoome reported that bhyve is gcc9 clean with the proposed fix.
Updated by Patrick Mooney almost 3 years ago
I fired up bhyve on a hardware machine and confirmed that my test instance booted and ran fine. Inspecting the VMCB under mdb -k yielded the expected contents.
Updated by Patrick Mooney almost 3 years ago
Mike Zeller has also tested this in his environment, running VMs over the weekend on platform featuring the change.
Updated by Electric Monk almost 3 years ago
- Status changed from In Progress to Closed
- % Done changed from 0 to 100
git commit a517c69d55a640319d65033c3b1275bb8a9c56ab
commit a517c69d55a640319d65033c3b1275bb8a9c56ab
Author: Patrick Mooney <pmooney@pfmooney.com>
Date: 2020-07-15T04:47:00.000Z
12939 avoid packing and bitfields in bhyve VMCB
Reviewed by: Mike Zeller <mike.zeller@joyent.com>
Reviewed by: Toomas Soome <tsoome@me.com>
Reviewed by: Andy Fiddaman <andy@omniosce.org>
Approved by: Dan McDonald <danmcd@joyent.com>
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