Messages in this thread | | | Date | Tue, 28 Apr 2015 14:56:45 +0200 | From | Christoffer Dall <> | Subject | Re: [PATCH v2 06/10] KVM: arm64: guest debug, add SW break point support |
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On Tue, Apr 28, 2015 at 10:34:12AM +0100, Peter Maydell wrote: > On 28 April 2015 at 09:42, Alex Bennée <alex.bennee@linaro.org> wrote: > > Peter Maydell <peter.maydell@linaro.org> writes: > >> Does the kernel already have a conveniently implemented "inject > >> exception into guest" lump of code? If so it might be less effort > >> to do it that way round, maybe. > > > > So you pointed out we can't just re-inject the exceptions we get as we > > need to map from things like ESR_ELx_EC_WATCHPT_LOW to > > ESR_ELx_EC_WATCHPT_CUR before re-injection. > > > > Of course if it is as simple as modifying the ESR_EL1 register and > > returning +ve in the handle_exit path then I can do that but I assumed > > if any other wrangling needs doing it should be done in userspace. > > Well, somebody's got to do it, and it's the same amount of work > either way (fiddling with ESR, making sure we direct the guest > to the right exception vector entry point, maybe a few other > things). > We already have code in the kernel to inject data/instruction aborts, but not sure how much benefit there is in re-using that. It's up to you really, but I think the kernel code should be clear about what the intention is so that we don't end up in a situation where: (1) The intended behavior is unclear/vague, and (2) it doesn't actually work in practice so nobody can follow the code.
Thanks, -Christoffer
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