From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "seanjc@google.com" <seanjc@google.com>,
"Zhao, Yan Y" <yan.y.zhao@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"Annapurve, Vishal" <vannapurve@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"michael.roth@amd.com" <michael.roth@amd.com>,
"Weiny, Ira" <ira.weiny@intel.com>
Subject: Re: [RFC PATCH 05/12] KVM: TDX: Drop superfluous page pinning in S-EPT management
Date: Thu, 28 Aug 2025 02:05:15 +0000 [thread overview]
Message-ID: <aa1835299cfd79788572a212761d8838c388ed37.camel@intel.com> (raw)
In-Reply-To: <aK7CvEcYXhr/p2wY@yzhao56-desk.sh.intel.com>
On Wed, 2025-08-27 at 16:33 +0800, Yan Zhao wrote:
> On Tue, Aug 26, 2025 at 05:05:15PM -0700, Sean Christopherson wrote:
> > Don't explicitly pin pages when mapping pages into the S-EPT, guest_memfd
> > doesn't support page migration in any capacity, i.e. there are no migrate
> > callbacks because guest_memfd pages *can't* be migrated. See the WARN in
> > kvm_gmem_migrate_folio().
> Hmm, we implemented exactly the same patch at [1], where we explained the
> potential problems of not holding page refcount, and the explored various
> approaches, and related considerations.
>
> [1] https://lore.kernel.org/all/20250807094241.4523-1-yan.y.zhao@intel.com/
Yea, so the outcome of the huge page related discussion was that we should look
at some sort of emergency page reclaim feature for the TDX module to use in the
case of bugs. But in the meantime to move forward without it, using a solution
like in this patch.
next prev parent reply other threads:[~2025-08-28 2:05 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-27 0:05 [RFC PATCH 00/12] KVM: x86/mmu: TDX post-populate cleanups Sean Christopherson
2025-08-27 0:05 ` [RFC PATCH 01/12] KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings Sean Christopherson
2025-08-27 8:14 ` Yan Zhao
2025-08-28 0:37 ` Ira Weiny
2025-08-28 2:13 ` Huang, Kai
2025-08-27 0:05 ` [RFC PATCH 02/12] KVM: x86/mmu: Add dedicated API to map guest_memfd pfn into TDP MMU Sean Christopherson
2025-08-27 8:25 ` Yan Zhao
2025-08-28 0:54 ` Edgecombe, Rick P
2025-08-28 1:26 ` Edgecombe, Rick P
2025-08-28 6:23 ` Yan Zhao
2025-08-28 19:40 ` Sean Christopherson
2025-08-29 1:16 ` Yan Zhao
2025-09-01 0:39 ` Yan Zhao
2025-08-28 6:55 ` Yan Zhao
2025-08-28 0:40 ` Ira Weiny
2025-08-28 1:51 ` Edgecombe, Rick P
2025-08-28 19:57 ` Sean Christopherson
2025-08-27 0:05 ` [RFC PATCH 03/12] Revert "KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU" Sean Christopherson
2025-08-27 0:05 ` [RFC PATCH 04/12] KVM: x86/mmu: Rename kvm_tdp_map_page() to kvm_tdp_prefault_page() Sean Christopherson
2025-08-28 2:01 ` Edgecombe, Rick P
2025-08-28 18:50 ` Sean Christopherson
2025-08-28 19:04 ` Edgecombe, Rick P
2025-08-27 0:05 ` [RFC PATCH 05/12] KVM: TDX: Drop superfluous page pinning in S-EPT management Sean Christopherson
2025-08-27 8:33 ` Yan Zhao
2025-08-28 2:05 ` Edgecombe, Rick P [this message]
2025-08-28 20:16 ` Sean Christopherson
2025-08-28 0:36 ` Ira Weiny
2025-08-28 7:08 ` Yan Zhao
2025-08-28 15:54 ` Ira Weiny
2025-08-28 2:45 ` Huang, Kai
2025-08-27 0:05 ` [RFC PATCH 06/12] KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG_ON() condition Sean Christopherson
2025-08-27 8:39 ` Yan Zhao
2025-08-27 17:26 ` Sean Christopherson
2025-08-28 2:11 ` Edgecombe, Rick P
2025-08-28 19:21 ` Sean Christopherson
2025-08-28 20:13 ` Edgecombe, Rick P
2025-08-28 21:00 ` Sean Christopherson
2025-08-28 21:19 ` Edgecombe, Rick P
2025-08-28 21:34 ` Sean Christopherson
2025-08-28 15:03 ` Ira Weiny
2025-08-27 0:05 ` [RFC PATCH 07/12] KVM: TDX: Avoid a double-KVM_BUG_ON() in tdx_sept_zap_private_spte() Sean Christopherson
2025-08-28 2:19 ` Edgecombe, Rick P
2025-08-28 14:50 ` Edgecombe, Rick P
2025-08-29 1:10 ` Yan Zhao
2025-08-28 15:02 ` Ira Weiny
2025-08-27 0:05 ` [RFC PATCH 08/12] KVM: TDX: Use atomic64_dec_return() instead of a poor equivalent Sean Christopherson
2025-08-28 2:56 ` Edgecombe, Rick P
2025-08-28 6:48 ` Yan Zhao
2025-08-28 19:14 ` Edgecombe, Rick P
2025-08-28 22:33 ` Sean Christopherson
2025-08-28 23:18 ` Edgecombe, Rick P
2025-08-28 15:03 ` Ira Weiny
2025-08-27 0:05 ` [RFC PATCH 09/12] KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller Sean Christopherson
2025-08-27 9:02 ` Yan Zhao
2025-08-27 19:08 ` Sean Christopherson
2025-08-28 3:13 ` Edgecombe, Rick P
2025-08-28 5:56 ` Yan Zhao
2025-08-28 19:08 ` Edgecombe, Rick P
2025-08-28 5:43 ` Yan Zhao
2025-08-28 17:00 ` Sean Christopherson
2025-08-28 18:52 ` Edgecombe, Rick P
2025-08-28 20:26 ` Sean Christopherson
2025-08-28 21:33 ` Edgecombe, Rick P
2025-08-28 21:57 ` Sean Christopherson
2025-08-28 23:17 ` Edgecombe, Rick P
2025-08-29 6:08 ` Yan Zhao
2025-08-28 22:06 ` Ira Weiny
2025-08-28 23:17 ` Sean Christopherson
2025-08-29 0:35 ` Ira Weiny
2025-08-29 6:06 ` Yan Zhao
2025-08-28 21:44 ` Sean Christopherson
2025-08-29 2:42 ` Binbin Wu
2025-08-29 2:31 ` Yan Zhao
2025-08-29 6:33 ` Yan Zhao
2025-08-28 15:30 ` Ira Weiny
2025-08-28 15:28 ` Ira Weiny
2025-08-27 0:05 ` [RFC PATCH 10/12] KVM: TDX: Assert that slots_lock is held when nr_premapped is accessed Sean Christopherson
2025-08-27 0:05 ` [RFC PATCH 11/12] KVM: TDX: Track nr_premapped as an "unsigned long", not an "atomic64_t" Sean Christopherson
2025-08-27 9:12 ` Yan Zhao
2025-08-27 0:05 ` [RFC PATCH 12/12] KVM: TDX: Rename nr_premapped to nr_pending_tdh_mem_page_adds Sean Christopherson
2025-08-27 9:22 ` Yan Zhao
2025-08-28 15:23 ` Ira Weiny
2025-08-27 9:48 ` [RFC PATCH 00/12] KVM: x86/mmu: TDX post-populate cleanups Yan Zhao
2025-08-28 19:01 ` Edgecombe, Rick P
2025-08-28 23:19 ` Sean Christopherson
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