linux-kernel - Re: [PATCH v2 3/6] KVM: x86: Remove the KVM_GET_NR_MMU

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Date:   Wed, 8 Feb 2023 14:48:51 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Thomas Huth <thuth@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Gavin Shan <gshan@...hat.com>,
        Steven Price <steven.price@....com>,
        Cornelia Huck <cohuck@...hat.com>
Subject: Re: [PATCH v2 3/6] KVM: x86: Remove the KVM_GET_NR_MMU_PAGES ioctl

On Wed, Feb 08, 2023, Thomas Huth wrote:
> The KVM_GET_NR_MMU_PAGES ioctl is quite questionable on 64-bit hosts
> since it fails to return the full 64 bits of the value that can be
> set with the corresponding KVM_SET_NR_MMU_PAGES call. Its "long" return
> value is truncated into an "int" in the kvm_arch_vm_ioctl() function.
> 
> Since this ioctl also never has been used by userspace applications
> (QEMU, Google's internal VMM, kvmtool and CrosVM have been checked),
> it's likely the best if we remove this badly designed ioctl before
> anybody really tries to use it.
> 
> Signed-off-by: Thomas Huth <thuth@...hat.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>