linux-kernel - RE: [PATCH v2 2/2] KVM: arm64: Add memcg accounting to KVM allocations

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Date:   Thu, 9 Sep 2021 12:56:53 +0000
From:   Justin He <Justin.He@....com>
To:     Oliver Upton <oupton@...gle.com>
CC:     Marc Zyngier <maz@...nel.org>, James Morse <James.Morse@....com>,
        Alexandru Elisei <Alexandru.Elisei@....com>,
        Suzuki Poulose <Suzuki.Poulose@....com>,
        Xiaoming Ni <nixiaoming@...wei.com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Liu Shixin <liushixin2@...wei.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Will Deacon <will@...nel.org>,
        "kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v2 2/2] KVM: arm64: Add memcg accounting to KVM
 allocations

Hi Oliver, thanks for the review, please my comments below:

> -----Original Message-----
> From: Oliver Upton <oupton@...gle.com>
> Sent: Wednesday, September 8, 2021 6:29 AM
> To: Justin He <Justin.He@....com>
> Cc: Marc Zyngier <maz@...nel.org>; James Morse <James.Morse@....com>;
> Alexandru Elisei <Alexandru.Elisei@....com>; Suzuki Poulose
> <Suzuki.Poulose@....com>; Xiaoming Ni <nixiaoming@...wei.com>; Lorenzo
> Pieralisi <Lorenzo.Pieralisi@....com>; Kees Cook <keescook@...omium.org>;
> Catalin Marinas <Catalin.Marinas@....com>; Nick Desaulniers
> <ndesaulniers@...gle.com>; linux-kernel@...r.kernel.org; Liu Shixin
> <liushixin2@...wei.com>; Sami Tolvanen <samitolvanen@...gle.com>; Will
> Deacon <will@...nel.org>; kvmarm@...ts.cs.columbia.edu; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH v2 2/2] KVM: arm64: Add memcg accounting to KVM
> allocations
> 
> Hi Jia,
> 
> On Tue, Sep 7, 2021 at 7:33 AM Jia He <justin.he@....com> wrote:
> >
> > Inspired by commit 254272ce6505 ("kvm: x86: Add memcg accounting to KVM
> > allocations"), it would be better to make arm64 KVM consistent with
> > common kvm codes.
> >
> > The memory allocations of VM scope should be charged into VM process
> > cgroup, hence change GFP_KERNEL to GFP_KERNEL_ACCOUNT.
> >
> > There remain a few cases since these allocations are global, not in VM
> > scope.
> 
> I believe there are more memory allocations that could be switched to
> GFP_KERNEL_ACCOUNT. For non-pKVM kernels, we probably should charge
> all stage-2 paging structure allocations to the VM process. Your patch
> appears to only change the allocation of the kvm_pgtable structure,
> but not descendent paging structures.
> 
Do you mean kvm_hyp_zalloc_page() here?
Seems kvm_hyp_zalloc_page() is in both global and VM scopes.

I will replace GFP_KERNEL with XXX_ACCOUNT in next version if no one 
objects that.

--
Cheers,
Justin (Jia He)