linux-kernel - Re: [PATCH v2 3/6] x86/kvm: introduce per cpu vcpu masks

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Message-ID: <b73693a6-d43c-ec58-91d0-c07ef5ea71ee@suse.com>
Date:   Mon, 6 Sep 2021 06:34:57 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Eduardo Habkost <ehabkost@...hat.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        maz@...nel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...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>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 3/6] x86/kvm: introduce per cpu vcpu masks

On 03.09.21 18:05, Eduardo Habkost wrote:
> On Fri, Sep 03, 2021 at 03:08:04PM +0200, Juergen Gross wrote:
>> In order to support high vcpu numbers per guest don't use on stack
>> vcpu bitmasks. As all those currently used bitmasks are not used in
>> functions subject to recursion it is fairly easy to replace them with
>> percpu bitmasks.
>>
>> Disable preemption while such a bitmask is being used in order to
>> avoid double usage in case we'd switch cpus.
>>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
> 
> Note that there's another patch that will introduce another
> KVM_MAX_VCPUS bitmap variable on the stack:
> https://lore.kernel.org/lkml/20210827092516.1027264-7-vkuznets@redhat.com/
> 
> Considering that the patch is a bug fix, should this series be
> rebased on top of that?
> 

Yes, I can do that.


Juergen

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