linux-kernel - Re: [PATCH] KVM: x86: enable TDP MMU by default

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Message-ID: <CANgfPd_Hzr77ywspQn3ee1PTWp2fKZ=maiwztJj2uvHNAsWqjw@mail.gmail.com>
Date:   Mon, 26 Jul 2021 09:53:02 -0700
From:   Ben Gardon <bgardon@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        David Matlack <dmatlack@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH] KVM: x86: enable TDP MMU by default

On Mon, Jul 26, 2021 at 9:31 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> With the addition of fast page fault support, the TDP-specific MMU has reached
> feature parity with the original MMU.  All my testing in the last few months
> has been done with the TDP MMU; switch the default on 64-bit machines.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Yay! Thank you for your support in getting this merged and enabled
Paolo, and thanks to David and Sean for helping upstream code and for
so many reviews!
I'm sure this will provoke some bug reports, and I'll keep a close eye
on the mailing list to help address the issues quickly.
In the meantime,

Reviewed-by: Ben Gardon <bgardon@...gle.com>

> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index f86158d41af0..43f12f5d12c0 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -10,7 +10,7 @@
>  #include <asm/cmpxchg.h>
>  #include <trace/events/kvm.h>
>
> -static bool __read_mostly tdp_mmu_enabled = false;
> +static bool __read_mostly tdp_mmu_enabled = true;
>  module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644);
>
>  /* Initializes the TDP MMU for the VM, if enabled. */
> --
> 2.27.0
>