linux-kernel - Re: [PATCH v10 056/108] KVM: TDX: don't request KVM_REQ_APIC_PAGE

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Message-ID: <1e5e5cb0ff43e52f630ec5c890204174be2582c5.camel@intel.com>
Date:   Fri, 16 Dec 2022 00:31:52 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
CC:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>
Subject: Re: [PATCH v10 056/108] KVM: TDX: don't request
 KVM_REQ_APIC_PAGE_RELOAD

On Thu, 2022-12-15 at 16:11 -0800, Isaku Yamahata wrote:
> > Btw2, by saying above, does it make sense to split patch "[PATCH v10
> > 105/108]
> > KVM: TDX: Add methods to ignore accesses to CPU state" based on category
> > such as
> > MMU/interrupt, etc?  Particularly, in that patch, some callbacks have WARN()
> > or
> > KVM_BUG_ON() against TD guest, but some don't.  The logic behind those
> > decisions
> > highly depend on previous patches.  To me, it makes more sense to just move
> > logic related things together.
> 
> Ok, I'll split it up to cpu states/KVM MMU/interrupt parts.

If I recall correctly, originally (long time ago before starting to upstream),
what we did was we have a patch to make all kvm_x86_ops callback KVM_BUG_ON()
for TDX guest, then we fix those KVM_BUG_ON() in later patches in separate
patches.

We don't need to do the exact same way, but this also seems reasonable to me. 
For instance, at the beginning we can mark KVM_BUG_ON() for all callbacks which
reads/writes CPU states (which is reasonable anyway), and in later patches we
remove the KVM_BUG_ON() if needed when handling specific logic.

Simply my 2cents above.  Just for your reference.  My real comment is we should
put relevant parts together so it's easy to review.