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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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
> 
>