Re: Subject: [RFC PATCH] kvm/x86: Fix 'lpages' kvm stat for TDM MMU

From: Paolo Bonzini <pbonzini@redhat.com>
To: "Shahin, Md Shahadat Hossain" <shahinmd@amazon.de>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Cc: "Szczepanek, Bartosz" <bsz@amazon.de>,
	"seanjc@google.com" <seanjc@google.com>,
	"bgardon@google.com" <bgardon@google.com>
Subject: Re: Subject: [RFC PATCH] kvm/x86: Fix 'lpages' kvm stat for TDM MMU
Date: Thu, 29 Apr 2021 17:39:08 +0200	[thread overview]
Message-ID: <dae9be92-00ab-2a2d-822b-e15abea6aeb6@redhat.com> (raw)
In-Reply-To: <1619700409955.15104@amazon.de>

On 29/04/21 14:46, Shahin, Md Shahadat Hossain wrote:
> Large pages not being created properly may result in increased memory
> access time. The 'lpages' kvm stat used to keep track of the current
> number of large pages in the system, but with TDP MMU enabled the stat
> is not showing the correct number.
> 
> This patch extends the lpages counter to cover the TDP case.
> 
> Signed-off-by: Md Shahadat Hossain Shahin <shahinmd@amazon.de>
> Cc: Bartosz Szczepanek <bsz@amazon.de>
> ---
>   arch/x86/kvm/mmu/tdp_mmu.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 34207b874886..1e2a3cb33568 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -425,6 +425,12 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
>   
>   	if (old_spte == new_spte)
>   		return;
> +	
> +	if (is_large_pte(old_spte))
> +		--kvm->stat.lpages;
> +	
> +	if (is_large_pte(new_spte))
> +		++kvm->stat.lpages;
>   
>   	trace_kvm_tdp_mmu_spte_changed(as_id, gfn, level, old_spte, new_spte);
>   
> 

Queued, thanks.

Paolo