Messages in this thread | | | From | Peter Maydell <> | Date | Fri, 15 May 2015 16:17:46 +0100 | Subject | Re: [PATCH v4 03/12] KVM: arm64: guest debug, define API headers |
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On 15 May 2015 at 16:14, Alex Bennée <alex.bennee@linaro.org> wrote: > > Mark Rutland <mark.rutland@arm.com> writes: > >> On Fri, May 15, 2015 at 03:27:06PM +0100, Alex Bennée wrote: >>> +/* >>> + * See v8 ARM ARM D7.3: Debug Registers >>> + * >>> + * The control registers are architecturally defined as 32 bits but are >>> + * stored as 64 bit values alongside the value registers. This is done >> >> Stale comment? They're stored as __u32 below. > > Gah yes it is. > >> It's possible that the registers could grow in future as happened in the >> case of CLIDR_EL1, so it might be worth treating system registers >> generally as u64 values. > > Really? I mean the existing debug *control* registers have reserved bits > 24-31 so there is space for expansion.
Other places in the userspace ABI which deal with sysregs (notably ONE_REG) consistently define them all as 64-bit (which makes sense anyway since the ISA only provides 64-bit accessors to them). "Architecturally 32 bits" only means "top 32 bits reserved".
-- PMM
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