linux-kernel - Re: [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf page ready notifications

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b1297936-cf69-227b-d758-c3f3ca09ae5d@redhat.com>
Date:   Thu, 30 Apr 2020 08:49:41 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf
 page ready notifications

On 29/04/20 11:36, Vitaly Kuznetsov wrote:
> +	case MSR_KVM_ASYNC_PF_ACK:
> +		if (data & 0x1)
> +			kvm_check_async_pf_completion(vcpu);
> +		break;

Does this work if interrupts are turned off?  I think in that case
kvm_check_async_pf_completion will refuse to make progress.  You need to
make this bit stateful (e.g. 1 = async PF in progress, 0 = not in
progress), and check that for page ready notifications instead of
EFLAGS.IF.  This probably means that;

- it might be simpler to move it to the vector MSR

- it's definitely much simpler to remove the #PF-based mechanism for
injecting page ready notifications.

Thanks,

Paolo