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Date: Fri, 3 Mar 2023 11:39:05 +0000
From: Jean-Philippe Brucker <jpb@kernel.org>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Itaru Kitayama <itaru.kitayama@gmail.com>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, kvmarm@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Andrew Jones <andrew.jones@linux.dev>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Chao Peng <chao.p.peng@linux.intel.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	Fuad Tabba <tabba@google.com>, James Morse <james.morse@arm.com>,
	Joey Gouly <Joey.Gouly@arm.com>, Marc Zyngier <maz@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Quentin Perret <qperret@google.com>,
	Sean Christopherson <seanjc@google.com>,
	Steven Price <steven.price@arm.com>, Thomas Huth <thuth@redhat.com>,
	Will Deacon <will@kernel.org>, Zenghui Yu <yuzenghui@huawei.com>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [RFC] Support for Arm CCA VMs on Linux
Message-ID: <20230303113905.GD361458@myrica>
References: <20230127112248.136810-1-suzuki.poulose@arm.com>
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 <CANW9uysnvGCwANu+_6dp9+3rvHGOkThT9d0K2qpQV4exdmYWoA@mail.gmail.com>
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In-Reply-To: <1c91b777-982e-e71a-4829-51744e9555c5@arm.com>

On Fri, Mar 03, 2023 at 09:54:47AM +0000, Suzuki K Poulose wrote:
> On 03/03/2023 09:46, Jean-Philippe Brucker wrote:
> > On Thu, Mar 02, 2023 at 07:12:24AM +0900, Itaru Kitayama wrote:
> > > > > I've tried your series in Real on CCA Host, but the KVM arch init
> > > > > emits an Invalid argument error and terminates.
> > 
> > This was the KVM_SET_ONE_REG for the SVE vector size. During my tests I
> > didn't enable SVE in the host but shrinkwrap enables more options.
> 
> Does the Qemu check for SVE capability on /dev/kvm ? For kvmtool, we
> changed to using the VM instance and that would prevent using SVE,
> until the RMM supports it.

Yes, QEMU does check the SVE cap on /dev/kvm. I can propose changing it or
complementing it with a VM check in my next version, it seems to work
(though I need to double-check the VM fd lifetime). Same goes for
KVM_CAP_STEAL_TIME, which I need to disable explicitly at the moment.

Thanks,
Jean

> 
> Suzuki
> 
> > 
> > Until we figure out support for SVE, disable it on the QEMU command-line
> > (similarly to '--disable-sve' needed for kvmtool boot):
> > 
> > 	-cpu host,sve=off
> > 
> > Thanks,
> > Jean
> 
>