linux-kernel - Re: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM

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Message-ID: <CAFEAcA-AKpkzSpMofMFxxf5XdYPii3PTB8xXDAvmyFWno7nZeA@mail.gmail.com>
Date:   Mon, 17 Sep 2018 15:20:15 +0100
From:   Peter Maydell <peter.maydell@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        kvmarm@...ts.cs.columbia.edu, kvm-devel <kvm@...r.kernel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <cdall@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Dave P Martin <dave.martin@....com>, julien.grall@....com,
        lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address
 size for VM

On 17 September 2018 at 11:41, Suzuki K Poulose <suzuki.poulose@....com> wrote:
> Allow specifying the physical address size limit for a new
> VM via the kvm_type argument for the KVM_CREATE_VM ioctl. This
> allows us to finalise the stage2 page table as early as possible
> and hence perform the right checks on the memory slots
> without complication. The size is ecnoded as Log2(PA_Size) in
> bits[7:0] of the type field. For backward compatibility the
> value 0 is reserved and implies 40bits. Also, lift the limit
> of the IPA to host limit and allow lower IPA sizes (e.g, 32).
>
> The userspace could check the extension KVM_CAP_ARM_VM_PHYS_SHIFT
> for the availability of this feature. The cap check returns the
> maximum limit for the physical address shift supported by the host.
>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Christoffer Dall <cdall@...nel.org>
> Cc: Peter Maydel <peter.maydell@...aro.org>

Typo: my surname has two "l"s in it.

thanks
-- PMM