Accesses to system registers are disproportionately heavy-weight
when executed under virtualization, since each one involves two
world switches (from guest to host and back again).
So change the sequence that enables the GIC SRE interface so that
it performs only a single sysreg read to test whether the SRE
interface is enabled already, and only performs a write and an
additional read if that turns out not to be the case.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17596 6f19259b-4bc3-4df7-8a09-765794883524
Even if the CPU id registers indicate hardware support for the
System Register interface to the GIC, higher exception levels
may disable that interface and only allow access through MMIO.
So move the enabling of the SRE bit to the GIC version detection
routine: if we trigger an exception, we would have anyway at a
later stage, so the net effect is the same. However, if setting
the bit doesn't stick, it means we can switch to MMIO and proceed
normally otherwise.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16344 6f19259b-4bc3-4df7-8a09-765794883524
Ard Biesheuvel
Olivier Martin