audk/OvmfPkg/VirtHstiDxe/README.md

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# virtual machine platform hsti driver
This driver supports three tests.
## VIRT_HSTI_BYTE0_SMM_SMRAM_LOCK
Verify the SMM memory is properly locked down.
Supported platforms:
* Qemu Q35 (SMM_REQUIRE=TRUE builds).
## VIRT_HSTI_BYTE0_SMM_SECURE_VARS_FLASH
Verify the variable store is not writable for normal (not SMM) code.
Supported platforms:
* Qemu Q35 (SMM_REQUIRE=TRUE builds).
## VIRT_HSTI_BYTE0_READONLY_CODE_FLASH
Verify the firmware code is not writable for the guest.
Supported platforms:
* Qemu Q35
* Qemu PC
# qemu flash configuration
With qemu being configured properly flash behavior should be this:
configuration | OVMF_CODE.fd | OVMF_VARS.fd
-------------------------------|----------------|---------------
SMM_REQUIRE=TRUE, SMM mode | read-only | writable
SMM_REQUIRE=TRUE, normal mode | read-only (1) | read-only (2)
SMM_REQUIRE=FALSE | read-only (3) | writable
VIRT_HSTI_BYTE0_READONLY_CODE_FLASH will verify (1) + (3).
VIRT_HSTI_BYTE0_SMM_SECURE_VARS_FLASH will verify (2).
## qemu command line for SMM_REQUIRE=TRUE builds
```
qemu-system-x86-64 -M q35,smm=on,pflash0=code,pflash1=vars \
-blockdev node-name=code,driver=file,filename=OVMF_CODE.fd,read-only=on \
-blockdev node-name=vars,driver=file,filename=OVMF_VARS.fd \
-global driver=cfi.pflash01,property=secure,value=on \
[ ... more options here ... ]
```