From: David Matlack <dmatlack@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Borislav Petkov <bp@suse.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Randy Dunlap <rdunlap@infradead.org>,
Damien Le Moal <damien.lemoal@opensource.wdc.com>,
kvm list <kvm@vger.kernel.org>
Subject: Re: [PATCH 0/9] KVM: x86/mmu: Always enable the TDP MMU when TDP is enabled
Date: Tue, 16 Aug 2022 09:30:54 -0700 [thread overview]
Message-ID: <CALzav=eWhg=ZMxVcGf9w_svn1XaTZABN5VoFP3fgxPiHohaMFQ@mail.gmail.com> (raw)
In-Reply-To: <YvtSc9ofTg1z8tt7@worktop.programming.kicks-ass.net>
On Tue, Aug 16, 2022 at 1:17 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, Aug 15, 2022 at 04:01:01PM -0700, David Matlack wrote:
> > Patch 1 deletes the module parameter tdp_mmu and forces KVM to always
> > use the TDP MMU when TDP hardware support is enabled. The rest of the
> > patches are related cleanups that follow (although the kvm_faultin_pfn()
> > cleanups at the end are only tangentially related at best).
> >
> > The TDP MMU was introduced in 5.10 and has been enabled by default since
> > 5.15. At this point there are no known functionality gaps between the
> > TDP MMU and the shadow MMU, and the TDP MMU uses less memory and scales
> > better with the number of vCPUs. In other words, there is no good reason
> > to disable the TDP MMU.
>
> Then how are you going to test the shadow mmu code -- which I assume is
> still relevant for the platforms that don't have this hardware support
> you speak of?
TDP hardware support can still be disabled with module parameters
(kvm_intel.ept=N and kvm_amd.npt=N).
The tdp_mmu module parameter only controls whether KVM uses the TDP
MMU or shadow MMU *when TDP hardware is enabled*.
next prev parent reply other threads:[~2022-08-16 16:31 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 23:01 [PATCH 0/9] KVM: x86/mmu: Always enable the TDP MMU when TDP is enabled David Matlack
2022-08-15 23:01 ` [PATCH 1/9] " David Matlack
2022-08-17 10:05 ` Paolo Bonzini
2022-08-17 16:49 ` David Matlack
2022-08-17 16:53 ` Paolo Bonzini
2022-08-17 17:46 ` David Matlack
2022-08-15 23:01 ` [PATCH 2/9] KVM: x86/mmu: Drop kvm->arch.tdp_mmu_enabled David Matlack
2022-08-24 14:21 ` kernel test robot
2022-08-15 23:01 ` [PATCH 3/9] KVM: x86/mmu: Consolidate mmu_seq calculations in kvm_faultin_pfn() David Matlack
2022-08-15 23:01 ` [PATCH 4/9] KVM: x86/mmu: Rename __direct_map() to nonpaging_map() David Matlack
2022-08-15 23:01 ` [PATCH 5/9] KVM: x86/mmu: Separate TDP and non-paging fault handling David Matlack
2022-08-24 17:06 ` kernel test robot
2022-08-15 23:01 ` [PATCH 6/9] KVM: x86/mmu: Stop needlessly making MMU pages available for TDP MMU faults David Matlack
2022-08-15 23:01 ` [PATCH 7/9] KVM: x86/mmu: Handle "error PFNs" in kvm_faultin_pfn() David Matlack
2022-08-15 23:01 ` [PATCH 8/9] KVM: x86/mmu: Avoid memslot lookup during KVM_PFN_ERR_HWPOISON handling David Matlack
2022-08-15 23:01 ` [PATCH 9/9] KVM: x86/mmu: Try to handle no-slot faults during kvm_faultin_pfn() David Matlack
2022-08-15 23:09 ` David Matlack
2022-08-16 8:16 ` [PATCH 0/9] KVM: x86/mmu: Always enable the TDP MMU when TDP is enabled Peter Zijlstra
2022-08-16 16:30 ` David Matlack [this message]
2022-08-17 8:53 ` Peter Zijlstra
2022-08-17 10:01 ` Huang, Kai
2022-08-17 16:42 ` David Matlack
2022-08-17 23:36 ` Huang, Kai
2022-08-16 22:54 ` David Matlack
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