Hi Marc, On 2020/2/14 22:57, Marc Zyngier wrote:
To allow the direct injection of SGIs into a guest, the GICv4.1 architecture has to sacrifice the Active state so that SGIs look a lot like LPIs (they are injected by the same mechanism). In order not to break existing software, the architecture gives offers guests OSs the choice: SGIs with or without an active state. It is the hypervisors duty to honor the guest's choice. For this, the architecture offers a discovery bit indicating whether the GIC supports GICv4.1 SGIs (GICD_TYPER2.nASSGIcap), and another bit indicating whether the guest wants Active-less SGIs or not (controlled by GICD_CTLR.nASSGIreq). A hypervisor not supporting GICv4.1 SGIs would leave nASSGIcap clear, and a guest not knowing about GICv4.1 SGIs (or definitely wanting an Active state) would leave nASSGIreq clear (both being thankfully backward compatible with oler revisions of the GIC).
older?
Since Linux is perfectly happy without an active state on SGIs, inform the hypervisor that we'll use that if offered. Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Per the description of these two bits in the commit message, Reviewed-by: Zenghui Yu <yuzenghui@xxxxxxxxxx> Thanks
