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From: Alexander Graf <agraf@suse.de>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm <qemu-arm@nongnu.org>, "Tom Rini" <trini@konsulko.com>,
	"Michal Simek" <michal.simek@xilinx.com>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Stephen Warren" <swarren@wwwdotorg.org>,
	"Alex Bennée" <alex.bennee@linaro.org>
Subject: Re: [Qemu-devel] [PATCH] target/arm: Allow to switch from MON->HYP on AArch32
Date: Wed, 9 Jan 2019 18:14:10 +0100	[thread overview]
Message-ID: <92dba7da-f3fc-b7dc-6896-cf8d58cc7f17@suse.de> (raw)
In-Reply-To: <CAFEAcA8Xzi8GjzUtzxbFzxdCS4kn0Cps+_bF70ZS0KnH0W8SvQ@mail.gmail.com>

On 01/09/2019 05:59 PM, Peter Maydell wrote:
> On Wed, 9 Jan 2019 at 16:52, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On Wed, 9 Jan 2019 at 15:26, Alexander Graf <agraf@suse.de> wrote:
>>> In U-boot, we switch from S-SVC -> MON -> HYP when we want to enter
>>> HYP mode. This dance seems to work ok (hence it's there in the code
>>> base), but breaks with current QEMU.
> PS: it would be helpful if the commit message said how u-boot
> is trying to go from Mon to Hyp -- some ways to try to do
> this are OK, and some are not, so whether it's supposed to
> work or not depends on what u-boot is actually doing...

I don't fully understand all of it to be honest :). But the code is here:

http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/cpu/armv7/nonsec_virt.S

What I managed to understand so far is that it goes to MON using the smc 
#0 call and then changes SPSR so that on return (movs pc) the mode will 
be different.

But please double check whether this is supposed to work - I don't find 
mode switching on ARM terribly intuitive ;).


Alex

  reply	other threads:[~2019-01-09 17:14 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 15:24 [Qemu-devel] [PATCH] target/arm: Allow to switch from MON->HYP on AArch32 Alexander Graf
2019-01-09 16:10 ` Alex Bennée
2019-01-09 16:19   ` Alexander Graf
2019-01-09 16:35   ` [Qemu-devel] [Qemu-arm] " Peter Maydell
2019-01-09 16:52 ` [Qemu-devel] " Peter Maydell
2019-01-09 16:59   ` Peter Maydell
2019-01-09 17:14     ` Alexander Graf [this message]
2019-01-09 23:08       ` Peter Maydell
2019-01-10  6:43         ` Alexander Graf
2019-01-10 10:34           ` Peter Maydell
2019-01-17 18:43             ` Peter Maydell

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