But does that mean that a guest should never be allowed to modify a
virtualized
timebase register, even if the hypervisor can support it?
The book3e mtspr writeup doesn't appear to specify the behavior when
writing to a read-only SPR, so perhaps you could argue that something
other
than a no-op is implementation-specific behavior.
v2.06 III-E 9.2.1:
"Writing the Time Base is hypervisor privileged."
v2.06 III-E 2.1:
"If a hypervisor-privileged register is accessed in the guest supervisor
state (MSR[GS PR] = 0b10), an Embedded Hypervisor Privilege exception
occurs."
(v2.06 III-E 5.4.1, the big SPR table, also shows the TB regs (for
writing,
i.e. 284 and 285) to be hypervisor privileged. Consistency, hurray :-)
)
Segher
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