On Mon, Jul 17, 2023 at 08:11:09PM -0300, Daniel Henrique Barboza wrote: > On 7/17/23 19:33, Conor Dooley wrote:
> > On Mon, Jul 17, 2023 at 06:54:17PM -0300, Daniel Henrique Barboza wrote: > > > Hi, > > > > > > I decided to include flags for both timer/counter extensions to make it > > > easier for us later on when dealing with the RVA22 profile (which > > > includes both). > > > > > > The features were already implemented by Atish Patra some time ago, but > > > back then these 2 extensions weren't introduced yet. This means that, > > > aside from extra stuff in riscv,isa FDT no other functional changes were > > > made. > > > > > > Both are defaulted to 'true' since QEMU already implements both > > > features, but the flag can be disabled if Zicsr isn't present or, in > > > the case of zihpm, if pmu_num = 0. > > > > Out of curiosity, since you are allowing them to be disabled, how do you > > intend to communicate to a guest that zicsr or zihpm are not present? > > At this point I'd say that existing guests are using other ways of checking > if these timers and counters are available. Or they just assume they're there as part of their baseline requirements ;) > After this patches OSes can confirm > if these timers are available via riscv,isa, but they can't assume that > they are not available if riscv,isa doesn't display them. > > There's a chance that guests will continue ignoring these 2 extensions > regardless > of whether the platform exposes them or not. > > > > > > This means that, > > > aside from extra stuff in riscv,isa FDT no other functional changes were > > > made. > > > > This is barely a "functional" change either, as the presence of these > > extensions has to be assumed, whether they appear in riscv,isa or not :/ > > It's more of an organizational change for the sake of QEMU internals because > the > RVA22 profile happens to include zicntr and zihpm as mandatory extensions. > It's > easier to add the flags than to document why we're claiming RVA22 support but > aren't displaying these 2 in riscv,isa. Possibly you should call out ACPI here too, since that does not suffer from the same issues as riscv,isa in DT, and putting zicntr/zihpm et al in the ISA string there is needed.
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