From: Isaku Yamahata <isaku.yamahata@intel.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "Yamahata, Isaku" <isaku.yamahata@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"seanjc@google.com" <seanjc@google.com>,
"Huang, Kai" <kai.huang@intel.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"sagis@google.com" <sagis@google.com>,
"isaku.yamahata@linux.intel.com" <isaku.yamahata@linux.intel.com>,
"Aktas, Erdem" <erdemaktas@google.com>,
"Zhao, Yan Y" <yan.y.zhao@intel.com>,
"isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
"dmatlack@google.com" <dmatlack@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/16] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU
Date: Fri, 17 May 2024 12:16:30 -0700 [thread overview]
Message-ID: <20240517191630.GC412700@ls.amr.corp.intel.com> (raw)
In-Reply-To: <d7b5a1e327d6a91e8c2596996df3ff100992dc6c.camel@intel.com>
On Fri, May 17, 2024 at 06:16:26PM +0000,
"Edgecombe, Rick P" <rick.p.edgecombe@intel.com> wrote:
> On Fri, 2024-05-17 at 02:03 -0700, Isaku Yamahata wrote:
> >
> > On top of your patch, I created the following patch to remove
> > kvm_gfn_for_root().
> > Although I haven't tested it yet, I think the following shows my idea.
> >
> > - Add gfn_shared_mask to struct tdp_iter.
> > - Use iter.gfn_shared_mask to determine the starting sptep in the root.
> > - Remove kvm_gfn_for_root()
>
> I investigated it.
Thanks for looking at it.
> After this, gfn_t's never have shared bit. It's a simple rule. The MMU mostly
> thinks it's operating on a shared root that is mapped at the normal GFN. Only
> the iterator knows that the shared PTEs are actually in a different location.
>
> There are some negative side effects:
> 1. The struct kvm_mmu_page's gfn doesn't match it's actual mapping anymore.
> 2. As a result of above, the code that flushes TLBs for a specific GFN will be
> confused. It won't functionally matter for TDX, just look buggy to see flushing
> code called with the wrong gfn.
flush_remote_tlbs_range() is only for Hyper-V optimization. In other cases,
x86_op.flush_remote_tlbs_range = NULL or the member isn't defined at compile
time. So the remote tlb flush falls back to flushing whole range. I don't
expect TDX in hyper-V guest. I have to admit that the code looks superficially
broken and confusing.
> 3. A lot of tracepoints no longer have the "real" gfn
Anyway we'd like to sort out trace points and pr_err() eventually because we
already added new pferr flags.
> 4. mmio spte doesn't have the shared bit, as previous (no effect)
> 5. Some zapping code (__tdp_mmu_zap_root(), tdp_mmu_zap_leafs()) intends to
> actually operating on the raw_gfn. It wants to iterate the whole EPT, so it goes
> from 0 to tdp_mmu_max_gfn_exclusive(). So now for mirrored it does, but for
> shared it only covers the shared range. Basically kvm_mmu_max_gfn() is wrong if
> we pretend shared GFNs are just strangely mapped normal GFNs. Maybe we could
> just fix this up to report based on GPAW for TDX? Feels wrong.
Yes, it's broken with kvm_mmu_max_gfn().
> On the positive effects side:
> 1. There is code that passes sp->gfn into things that it shouldn't (if it has
> shared bits) like memslot lookups.
> 2. Also code that passes iter.gfn into things it shouldn't like
> kvm_mmu_max_mapping_level().
>
> These places are not called by TDX, but if you know that gfn's might include
> shared bits, then that code looks buggy.
>
> I think the solution in the diff is more elegant then before, because it hides
> what is really going on with the shared root. That is both good and bad. Can we
> accept the downsides?
Kai, do you have any thoughts?
--
Isaku Yamahata <isaku.yamahata@intel.com>
next prev parent reply other threads:[~2024-05-17 19:16 UTC|newest]
Thread overview: 152+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-15 0:59 [PATCH 00/16] TDX MMU prep series part 1 Rick Edgecombe
2024-05-15 0:59 ` [PATCH 01/16] KVM: x86: Add a VM type define for TDX Rick Edgecombe
2024-05-15 0:59 ` [PATCH 02/16] KVM: x86/mmu: Introduce a slot flag to zap only slot leafs on slot deletion Rick Edgecombe
2024-05-15 13:24 ` Huang, Kai
2024-05-15 19:09 ` Sean Christopherson
2024-05-15 19:23 ` Edgecombe, Rick P
2024-05-15 20:05 ` Sean Christopherson
2024-05-15 20:53 ` Edgecombe, Rick P
2024-05-15 22:47 ` Sean Christopherson
2024-05-15 23:06 ` Huang, Kai
2024-05-15 23:20 ` Sean Christopherson
2024-05-15 23:36 ` Huang, Kai
2024-05-16 1:12 ` Xiaoyao Li
2024-05-17 15:30 ` Paolo Bonzini
2024-05-22 1:29 ` Yan Zhao
2024-05-22 2:31 ` Sean Christopherson
2024-05-22 6:48 ` Yan Zhao
2024-05-22 15:45 ` Paolo Bonzini
2024-05-24 1:50 ` Yan Zhao
2024-05-15 23:56 ` Edgecombe, Rick P
2024-05-16 2:21 ` Edgecombe, Rick P
2024-05-16 3:56 ` Yan Zhao
2024-05-17 15:27 ` Paolo Bonzini
2024-05-17 15:25 ` Paolo Bonzini
2024-05-15 18:03 ` Isaku Yamahata
2024-05-15 0:59 ` [PATCH 03/16] KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU Rick Edgecombe
2024-05-17 7:44 ` Chao Gao
2024-05-17 9:08 ` Isaku Yamahata
2024-05-15 0:59 ` [PATCH 04/16] KVM: x86/mmu: Add address conversion functions for TDX shared bit of GPA Rick Edgecombe
2024-05-15 22:34 ` Huang, Kai
2024-05-15 23:21 ` Edgecombe, Rick P
2024-05-15 23:31 ` Huang, Kai
2024-05-15 23:38 ` Edgecombe, Rick P
2024-05-15 23:44 ` Huang, Kai
2024-05-15 23:59 ` Edgecombe, Rick P
2024-05-16 0:12 ` Huang, Kai
2024-05-16 0:19 ` Edgecombe, Rick P
2024-05-16 0:25 ` Huang, Kai
2024-05-16 0:35 ` Edgecombe, Rick P
2024-05-16 1:04 ` Huang, Kai
2024-05-16 1:20 ` Edgecombe, Rick P
2024-05-16 1:40 ` Huang, Kai
2024-05-16 5:52 ` Yan Zhao
2024-05-18 0:25 ` Edgecombe, Rick P
2024-05-16 23:08 ` Edgecombe, Rick P
2024-05-17 0:37 ` Huang, Kai
2024-05-17 1:51 ` Edgecombe, Rick P
2024-05-17 4:26 ` Huang, Kai
2024-05-17 21:12 ` Edgecombe, Rick P
2024-05-15 0:59 ` [PATCH 05/16] KVM: Add member to struct kvm_gfn_range for target alias Rick Edgecombe
2024-05-17 20:58 ` Edgecombe, Rick P
2024-05-15 0:59 ` [PATCH 06/16] KVM: x86/mmu: Add a new is_private member for union kvm_mmu_page_role Rick Edgecombe
2024-05-15 0:59 ` [PATCH 07/16] KVM: x86/mmu: Add a private pointer to struct kvm_mmu_page Rick Edgecombe
2024-05-15 0:59 ` [PATCH 08/16] KVM: x86/mmu: Bug the VM if kvm_zap_gfn_range() is called for TDX Rick Edgecombe
2024-05-15 13:27 ` Huang, Kai
2024-05-15 15:22 ` Edgecombe, Rick P
2024-05-15 23:14 ` Huang, Kai
2024-05-15 15:34 ` Sean Christopherson
2024-05-15 15:49 ` Edgecombe, Rick P
2024-05-15 15:56 ` Edgecombe, Rick P
2024-05-15 16:02 ` Sean Christopherson
2024-05-15 16:12 ` Edgecombe, Rick P
2024-05-15 18:09 ` Sean Christopherson
2024-05-15 18:22 ` Edgecombe, Rick P
2024-05-15 19:48 ` Sean Christopherson
2024-05-15 20:32 ` Edgecombe, Rick P
2024-05-15 23:26 ` Sean Christopherson
2024-05-15 16:22 ` Isaku Yamahata
2024-05-15 22:17 ` Huang, Kai
2024-05-15 23:14 ` Edgecombe, Rick P
2024-05-15 23:38 ` Huang, Kai
2024-05-16 0:13 ` Edgecombe, Rick P
2024-05-16 0:27 ` Isaku Yamahata
2024-05-16 1:11 ` Huang, Kai
2024-05-16 0:15 ` Isaku Yamahata
2024-05-16 0:52 ` Edgecombe, Rick P
2024-05-16 1:21 ` Huang, Kai
2024-05-16 17:27 ` Isaku Yamahata
2024-05-16 21:46 ` Edgecombe, Rick P
2024-05-16 22:23 ` Huang, Kai
2024-05-16 22:38 ` Edgecombe, Rick P
2024-05-16 23:16 ` Huang, Kai
2024-05-15 0:59 ` [PATCH 09/16] KVM: x86/mmu: Make kvm_tdp_mmu_alloc_root() return void Rick Edgecombe
2024-05-15 0:59 ` [PATCH 10/16] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU Rick Edgecombe
2024-05-15 17:35 ` Isaku Yamahata
2024-05-15 18:00 ` Edgecombe, Rick P
2024-05-16 0:52 ` Huang, Kai
2024-05-16 1:27 ` Edgecombe, Rick P
2024-05-16 2:07 ` Huang, Kai
2024-05-16 2:57 ` Edgecombe, Rick P
2024-05-16 13:04 ` Huang, Kai
2024-05-16 16:36 ` Edgecombe, Rick P
2024-05-16 19:42 ` Isaku Yamahata
2024-05-17 2:35 ` Edgecombe, Rick P
2024-05-17 9:03 ` Isaku Yamahata
2024-05-17 18:16 ` Edgecombe, Rick P
2024-05-17 19:16 ` Isaku Yamahata [this message]
2024-05-20 23:32 ` Isaku Yamahata
2024-05-21 15:07 ` Edgecombe, Rick P
2024-05-21 16:15 ` Isaku Yamahata
2024-05-22 22:34 ` Isaku Yamahata
2024-05-22 23:09 ` Edgecombe, Rick P
2024-05-22 23:47 ` Isaku Yamahata
2024-05-22 23:50 ` Edgecombe, Rick P
2024-05-23 0:01 ` Isaku Yamahata
2024-05-23 18:27 ` Edgecombe, Rick P
2024-05-24 7:55 ` Isaku Yamahata
2024-05-28 16:27 ` Edgecombe, Rick P
2024-05-28 17:47 ` Paolo Bonzini
2024-05-29 2:13 ` Edgecombe, Rick P
2024-05-29 7:25 ` Paolo Bonzini
2024-05-31 14:11 ` Isaku Yamahata
2024-05-28 17:43 ` Paolo Bonzini
2024-05-28 17:16 ` Paolo Bonzini
2024-05-28 18:29 ` Edgecombe, Rick P
2024-05-29 1:06 ` Isaku Yamahata
2024-05-29 1:51 ` Edgecombe, Rick P
2024-05-17 2:36 ` Huang, Kai
2024-05-17 8:14 ` Isaku Yamahata
2024-05-18 5:42 ` Huang, Kai
2024-05-18 15:41 ` Edgecombe, Rick P
2024-05-20 10:38 ` Huang, Kai
2024-05-20 18:58 ` Isaku Yamahata
2024-05-20 19:02 ` Edgecombe, Rick P
2024-05-20 23:39 ` Edgecombe, Rick P
2024-05-21 2:25 ` Isaku Yamahata
2024-05-21 2:57 ` Edgecombe, Rick P
2024-05-20 22:34 ` Huang, Kai
2024-05-16 1:48 ` Isaku Yamahata
2024-05-16 2:00 ` Edgecombe, Rick P
2024-05-16 2:10 ` Huang, Kai
2024-05-28 16:59 ` Paolo Bonzini
2024-05-16 17:10 ` Isaku Yamahata
2024-05-23 23:14 ` Edgecombe, Rick P
2024-05-24 8:20 ` Isaku Yamahata
2024-05-28 21:48 ` Edgecombe, Rick P
2024-05-29 1:16 ` Isaku Yamahata
2024-05-29 1:50 ` Edgecombe, Rick P
2024-05-29 2:20 ` Isaku Yamahata
2024-05-29 2:29 ` Edgecombe, Rick P
2024-05-28 20:54 ` Edgecombe, Rick P
2024-05-29 1:24 ` Isaku Yamahata
2024-05-28 23:06 ` Edgecombe, Rick P
2024-05-29 1:57 ` Isaku Yamahata
2024-05-29 2:13 ` Edgecombe, Rick P
2024-05-29 16:55 ` Isaku Yamahata
2024-05-15 0:59 ` [PATCH 11/16] KVM: x86/tdp_mmu: Extract root invalid check from tdx_mmu_next_root() Rick Edgecombe
2024-05-15 0:59 ` [PATCH 12/16] KVM: x86/tdp_mmu: Introduce KVM MMU root types to specify page table type Rick Edgecombe
2024-05-15 0:59 ` [PATCH 13/16] KVM: x86/tdp_mmu: Introduce shared, private KVM MMU root types Rick Edgecombe
2024-05-15 0:59 ` [PATCH 14/16] KVM: x86/tdp_mmu: Take root types for kvm_tdp_mmu_invalidate_all_roots() Rick Edgecombe
2024-05-15 0:59 ` [PATCH 15/16] KVM: x86/tdp_mmu: Make mmu notifier callbacks to check kvm_process Rick Edgecombe
2024-05-15 0:59 ` [PATCH 16/16] KVM: x86/tdp_mmu: Invalidate correct roots Rick Edgecombe
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