linux-kernel - Re: [RFC PATCH 08/12] KVM: TDX: Use atomic64_dec

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Message-ID: <128a19f38bb532a91cfe23b7a7512bb883b276cd.camel@intel.com>
Date: Thu, 28 Aug 2025 19:14:24 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "michael.roth@....com"
	<michael.roth@....com>, "Weiny, Ira" <ira.weiny@...el.com>
Subject: Re: [RFC PATCH 08/12] KVM: TDX: Use atomic64_dec_return() instead of
 a poor equivalent

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.