From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "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>,
"seanjc@google.com" <seanjc@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 08/12] KVM: TDX: Use atomic64_dec_return() instead of a poor equivalent
Date: Thu, 28 Aug 2025 19:14:24 +0000 [thread overview]
Message-ID: <128a19f38bb532a91cfe23b7a7512bb883b276cd.camel@intel.com> (raw)
In-Reply-To: <aK/7rgrUdC2cBiYd@yzhao56-desk.sh.intel.com>
On Thu, 2025-08-28 at 14:48 +0800, Yan Zhao wrote:
> Hmm, I still think it's safer to keep the nr_premapped to detect any unexpected
> code change.
When I checking patch 6 I saw how many more KVM_BUG_ON()s we ended up with in
TDX code compared to the rest of KVM. (even after we dropped a bunch during
development) We have to differentiate from good safety, and "safety" that is
really just propping up brittle code. Each KVM_BUG_ON() is a hint that there
might be design issues.
next prev parent reply other threads:[~2025-08-28 19:14 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
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 [this message]
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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