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Re: softmmu 'at' instruction support


From: Janne Karhunen
Subject: Re: softmmu 'at' instruction support
Date: Fri, 19 Nov 2021 16:38:57 +0200

On Fri, Nov 19, 2021 at 4:28 PM Peter Maydell <peter.maydell@linaro.org> wrote:

> Note also that not all ELs have two TTBRs; some have only TTBR0,
> in which case you get figure D5-2, with just the starting-from-0
> part of the address space being valid.
>
> Big question: I thought we were talking about doing lookups
> on virtual address 0 here? That should be using TTBR0, so why
> do you expect it to be using TTBR1?

I suppose I wasn't entirely clear on the kernel/user mapping split, I
just did the second stage and didn't really care about what exactly
happens in the guest. Things seemed to be a bit more complicated than
I thought as bits above 48/52 were not ignored after all and made all
the difference on the table selection. I had the impression it was
just the calling context that defined the table to be used.


--
Janne



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