From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: allow compiling out SMM support
Date: Wed, 28 Sep 2022 14:59:27 +0000 [thread overview]
Message-ID: <YzRhT6DzgDfGU7NC@google.com> (raw)
In-Reply-To: <f708d769-5d93-351f-ea24-8fa7deb9f689@redhat.com>
On Wed, Sep 28, 2022, Paolo Bonzini wrote:
> On 9/27/22 19:59, Sean Christopherson wrote:
> > > static int kvm_vcpu_ioctl_smi(struct kvm_vcpu *vcpu)
> > > {
> > > - kvm_make_request(KVM_REQ_SMI, vcpu);
> > > -
> > > + if (IS_ENABLED(CONFIG_KVM_SMM))
> > > + kvm_make_request(KVM_REQ_SMI, vcpu);
> > > return 0;
> >
> > This should return -EINVAL, not 0.
>
> I'm a bit wary of changing this in case userspace is relying on it not
> failing, because the paths that lead to the failing ioctl are most likely
> controlled by the guest.
But with CONFIG_KVM_SMM=n, KVM is now reporting that KVM_CAP_X86_SMM is unsupported,
so it's firmly a VMM bug if userspace is blindly firing KVM_SMI. As long as the
Kconfig is on by default, I don't see any reason to fudge KVM's ABI to try to avoid
breaking buggy userspace.
/* Available with KVM_CAP_X86_SMM */
#define KVM_SMI _IO(KVMIO, 0xb7)
next prev parent reply other threads:[~2022-09-28 14:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-27 15:22 [PATCH] KVM: allow compiling out SMM support Paolo Bonzini
2022-09-27 17:59 ` Sean Christopherson
2022-09-28 11:41 ` Paolo Bonzini
2022-09-28 14:59 ` Sean Christopherson [this message]
2022-09-28 16:05 ` Paolo Bonzini
2022-09-29 15:49 ` Maciej S. Szmigiero
2022-09-29 16:47 ` Paolo Bonzini
2022-09-29 20:38 ` Sean Christopherson
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