linux-kernel - Re: [PATCH 4.14 108/159] kvm, mm: account kvm related kmem slabs to kmemcg

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Date:   Fri, 22 Dec 2017 10:34:07 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: Re: [PATCH 4.14 108/159] kvm, mm: account kvm related kmem slabs to
 kmemcg

On Fri 22-12-17 09:46:33, Greg KH wrote:
> 4.14-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Shakeel Butt <shakeelb@...gle.com>
> 
> 
> [ Upstream commit 46bea48ac241fe0b413805952dda74dd0c09ba8b ]
> 
> The kvm slabs can consume a significant amount of system memory
> and indeed in our production environment we have observed that
> a lot of machines are spending significant amount of memory that
> can not be left as system memory overhead. Also the allocations
> from these slabs can be triggered directly by user space applications
> which has access to kvm and thus a buggy application can leak
> such memory. So, these caches should be accounted to kmemcg.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

The patch is not marked for stable, neither it fixes an existing bug.
It is a nice to have thing for sure but I am wondering how this got
through stable-filter. 

> ---
>  arch/x86/kvm/mmu.c  |    4 ++--
>  virt/kvm/kvm_main.c |    2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -5476,13 +5476,13 @@ int kvm_mmu_module_init(void)
>  
>  	pte_list_desc_cache = kmem_cache_create("pte_list_desc",
>  					    sizeof(struct pte_list_desc),
> -					    0, 0, NULL);
> +					    0, SLAB_ACCOUNT, NULL);
>  	if (!pte_list_desc_cache)
>  		goto nomem;
>  
>  	mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
>  						  sizeof(struct kvm_mmu_page),
> -						  0, 0, NULL);
> +						  0, SLAB_ACCOUNT, NULL);
>  	if (!mmu_page_header_cache)
>  		goto nomem;
>  
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4018,7 +4018,7 @@ int kvm_init(void *opaque, unsigned vcpu
>  	if (!vcpu_align)
>  		vcpu_align = __alignof__(struct kvm_vcpu);
>  	kvm_vcpu_cache = kmem_cache_create("kvm_vcpu", vcpu_size, vcpu_align,
> -					   0, NULL);
> +					   SLAB_ACCOUNT, NULL);
>  	if (!kvm_vcpu_cache) {
>  		r = -ENOMEM;
>  		goto out_free_3;
> 

-- 
Michal Hocko
SUSE Labs