** Description changed:
The firmware descriptor file installed by the current ovmf-amdsev
package (2025.11-3ubuntu7) contains the following content.
/usr/share/qemu/firmware/60-edk2-x86_64-amdsev.json
---
{
"description": "UEFI firmware for x86_64, with SEV-ES support",
"interface-types": [
"uefi"
],
"mapping": {
"device": "flash",
"mode": "stateless",
"executable": {
"filename": "/usr/share/ovmf/OVMF.amdsev.fd",
"format": "raw"
}
},
"targets": [
{
"architecture": "x86_64",
"machines": [
"pc-q35-*"
]
}
],
"features": [
"amd-sev",
"amd-sev-es",
"amd-sev-snp",
"verbose-dynamic"
],
"tags": [
]
}
---
- Although "amd-sev-snp" appears in its feature list, this descriptor is not
compatible with SEV-SNP because only the rom type firmware is accepted.
- When an instance is created with SEV-SNP encryption and libvirt selects this
firmware, qemu fails to start due to the error "pflash with kvm requires KVM
readonly memory support".
+ Although "amd-sev-snp" appears in its feature list, this descriptor is
+ not compatible with SEV-SNP. For SEV-SNP instance only the rom type
+ firmware is accepted, but the descriptor makes libvirt to use pflash
+ type instead.
+
+ When an instance is created with SEV-SNP encryption and libvirt selects
+ this firmware, qemu fails to start due to the error "pflash with kvm
+ requires KVM readonly memory support".
To allow SEV-SNP instances launch properly, the mapping field should be
updated to:
---
...
"mapping": {
"device": "memory",
"filename": "/usr/share/edk2/ovmf/OVMF.amdsev.fd"
},
...
---
Note:
That "device": "memory" is the flag to tell libvirt to use the -bios option
in qemu, which is described in the qemu command line example in
https://ubuntu.com/server/docs/how-to/virtualisation/sev-snp/#host-configuration
.
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https://bugs.launchpad.net/bugs/2160129
Title:
Descriptor file for amd-sev is not compatible with SEV-SNP
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