From: Mark Rutland <mark.rutland@arm.com>
To: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
qemu-devel@nongnu.org, Dave Martin <Dave.Martin@arm.com>,
qemu-arm@nongnu.org, Guoheyi <guoheyi@huawei.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC] Add virtual SDEI support in qemu
Date: Mon, 15 Jul 2019 15:44:46 +0100 [thread overview]
Message-ID: <20190715144446.GK56232@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <4daefb19-6c15-f82c-31e9-1ae035d45bd5@arm.com>
On Mon, Jul 15, 2019 at 03:26:39PM +0100, James Morse wrote:
> On 15/07/2019 14:48, Mark Rutland wrote:
> > On Mon, Jul 15, 2019 at 02:41:00PM +0100, Dave Martin wrote:
> >> One option (suggested to me by James Morse) would be to allow userspace
> >> to disable in the in-kernel PSCI implementation and provide its own
> >> PSCI to the guest via SMC -- in which case userspace that wants to
> >> implement SDEI would have to implement PSCI as well.
> >
> > I think this would be the best approach, since it puts userspace in
> > charge of everything.
> >
> > However, this interacts poorly with FW-based mitigations that we
> > implement in hyp. I suspect we'd probably need a mechanism to delegate
> > that responsibility back to the kernel, and figure out if that has any
> > interaction with thigns that got punted to userspace...
>
> This has come up before:
> https://lore.kernel.org/r/59C139D0.3040507@arm.com
>
> I agree Qemu should opt-in to this, it needs to be a feature that is enabled.
>
> I had an early version of something like this for testing SDEI before
> there was firmware available. The review feedback from Christoffer was
> that it should include HVC and SMC, their immediates, and shouldn't be
> tied to SMC-CC ranges.
>
> I think this should be a catch-all as Heyi describes to deliver
> 'unhandled SMC/HVC' to user-space as hypercall exits. We should
> include the immediate in the struct.
>
> We can allow Qemu to disable the in-kernel PSCI implementation, which
> would let it be done in user-space via this catch-all mechanism. (PSCI
> in user-space has come up on another thread recently). The in-kernel
> PSCI needs to be default-on for backwards compatibility.
>
> As Mark points out, the piece that's left is the 'arch workaround'
> stuff. We always need to handle these in the kernel. I don't think
> these should be routed-back, they should be un-obtainable by
> user-space.
Sure; I meant that those should be handled in the kernel rather than
going to host userspace and back.
I was suggesting was that userspace would opt into taking ownership of
all HVC calls, then explicitly opt-in to the kernel handling specific
(sets of) calls.
There are probably issues with that, but I suspect defining "all
undandled calls" will be problematic otherwise.
Thanks,
Mark.
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next prev parent reply other threads:[~2019-07-15 14:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-13 9:53 [RFC] Add virtual SDEI support in qemu Guoheyi
2019-07-15 13:41 ` Dave Martin
2019-07-15 13:48 ` Mark Rutland
2019-07-15 14:26 ` James Morse
2019-07-15 14:44 ` Mark Rutland [this message]
2019-07-16 8:47 ` Dave Martin
2019-07-19 1:49 ` Guoheyi
2019-07-16 8:30 ` Dave Martin
2019-07-16 8:46 ` Marc Zyngier
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