linux-kernel - Re: [PATCH v4 2/2] KVM: nSVM: implement ondemand allocation of the nested state

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Message-ID: <d9c0d190-c6ea-2e21-92ca-2a53efb86a1d@redhat.com>
Date:   Sat, 19 Sep 2020 17:09:09 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4 2/2] KVM: nSVM: implement ondemand allocation of the
 nested state

On 17/09/20 18:29, Sean Christopherson wrote:
>> +				vcpu->arch.efer = old_efer;
>> +				kvm_make_request(KVM_REQ_OUT_OF_MEMORY, vcpu);
> I really dislike KVM_REQ_OUT_OF_MEMORY.  It's redundant with -ENOMEM and
> creates a huge discrepancy with respect to existing code, e.g. nVMX returns
> -ENOMEM in a similar situation.

Maxim, your previous version was adding some error handling to
kvm_x86_ops.set_efer.  I don't remember what was the issue; did you have
any problems propagating all the errors up to KVM_SET_SREGS (easy),
kvm_set_msr (harder) etc.?

Paolo