On Sun, Nov 21, 2021 at 11:33:43AM -0800, Greg Favor wrote:
What is the rationale for mandating any specific time period in OS-A-ish
The period can be determined by device tree and/or ACPI, at least one of
which is required for OS-A platforms, so the idea that a fixed period makes
things easier is debatable.
If the argument is that a fixed period is necessary for migration of
virtual machines using the hypervisor extension, then perhaps it should
only be a requirement when the hypervisor extension is also present.
As Anup (I believe) mentioned, mandating a specific period will make
non-compliant some existing platforms that would otherwise be compliant.
Maybe this isn't a strong factor, but it was my understanding that one goal
of the first iteration of the platform specifications was to cover, to the
extent possible, existing platforms (hence the legacy PLIC and 8250
requirements, as well).
It is also unfortunate that there is no opportunity for recommendations,
where this requirement could be phrased in such a way that it is not
required, but provides rationale to hopefully persuade platform
implementations to comply.