Hi Mark, On Wed, Dec 15, 2021 at 11:39:58AM +0000, Mark Rutland wrote: > Hi Oliver, > > On Tue, Dec 14, 2021 at 05:28:07PM +0000, Oliver Upton wrote: > > Any valid implementation of the architecture should generate an > > undefined exception for writes to a read-only register, such as > > OSLSR_EL1. Nonetheless, the KVM handler actually implements write-ignore > > behavior. > > > > Align the trap handler for OSLSR_EL1 with hardware behavior. If such a > > write ever traps to EL2, inject an undef into the guest and print a > > warning. > > I think this can still be read amibguously, since we don't explicitly state > that writes to OSLSR_EL1 should never trap (and the implications of being > UNDEFINED are subtle). How about: > > | Writes to OSLSR_EL1 are UNDEFINED and should never trap from EL1 to EL2, but > | the KVM trap handler for OSLSR_EL1 handlees writes via ignore_write(). This > | is confusing to readers of the code, but shouldn't have any functional impact. > | > | For clarity, use write_to_read_only() rather than ignore_write(). If a trap > | is unexpectedly taken to EL2 in violation of the architecture, this will > | WARN_ONCE() and inject an undef into the guest. Agreed, I like your suggested changelog better :-) > With that: > > Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Thanks! -- Best, Oliver
