linux-kernel - Re: [PATCH] kvm: x86: move srcu lock out of kvm_vcpu_check

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Message-ID: <3d3622c0-7c7a-3d24-d0f5-3204c5d105f9@redhat.com>
Date:   Thu, 20 May 2021 14:31:11 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Jon Kohler <jon@...anix.com>
Cc:     Bijan Mottahedeh <bijan.mottahedeh@...anix.com>,
        Raphael Norwitz <raphael.norwitz@...anix.com>,
        Junaid Shahid <junaids@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kvm: x86: move srcu lock out of kvm_vcpu_check_block

On 19/05/21 23:53, Sean Christopherson wrote:
>    1. Refactor check_nested_events() to split out a has_events() helper.
>    2. Move the has_events() call from kvm_vcpu_running() into kvm_vcpu_has_events()
>    3. Drop the explicit hv_timer_pending() in inject_pending_event().  It should
>       be dead code since it's just a pointer to nested_vmx_preemption_timer_pending(),
>       which is handled by vmx_check_nested_events() and called earlier.
>    4. Drop the explicit hv_timer_pending() in kvm_vcpu_has_events() for the same
>       reasons as (3).  This can also drop hv_timer_pending() entirely.

Sounds good except that I would do (3) first, since if I understand 
correctly it's a valid cleanup in the current code as well, and do (2) 
and (4) at the same time since you're basically enlarging the scope of 
the existing hv_timer_pending call to include all nested events.

Paolo