From: Jim Mattson <jmattson@google.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Joerg Roedel <joro@8bytes.org>, kvm list <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Weijiang Yang <weijiang.yang@intel.com>
Subject: Re: [RFC PATCH] KVM: x86: Disallow KVM_SET_CPUID{2} if the vCPU is in guest mode
Date: Wed, 18 Dec 2019 11:38:43 -0800 [thread overview]
Message-ID: <CALMp9eR-ssCUT_6oZntZ=-5SEN7Y8q-HnraKW=WDHuAn9gYZfQ@mail.gmail.com> (raw)
In-Reply-To: <20191218174255.30773-1-sean.j.christopherson@intel.com>
On Wed, Dec 18, 2019 at 9:42 AM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> Reject KVM_SET_CPUID{2} with -EBUSY if the vCPU is in guest mode (L2) to
> avoid complications and potentially undesirable KVM behavior. Allowing
> userspace to change a guest's capabilities while L2 is active would at
> best result in unexpected behavior in the guest (L1 or L2), and at worst
> induce bad KVM behavior by breaking fundamental assumptions regarding
> transitions between L0, L1 and L2.
This seems a bit contrived. As long as we're breaking the ABI, can we
disallow changes to CPUID once the vCPU has been powered on?
next prev parent reply other threads:[~2019-12-18 19:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-18 17:42 [RFC PATCH] KVM: x86: Disallow KVM_SET_CPUID{2} if the vCPU is in guest mode Sean Christopherson
2019-12-18 19:38 ` Jim Mattson [this message]
2019-12-18 20:10 ` Sean Christopherson
2019-12-18 20:57 ` Jim Mattson
2019-12-18 21:24 ` Sean Christopherson
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