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Message-ID: <ccf85ef8-049b-40a9-adcb-eac0cdc57b37@intel.com>
Date: Thu, 7 Mar 2024 13:11:15 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
<pbonzini@...hat.com>
CC: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Yan Zhao
<yan.y.zhao@...el.com>, Isaku Yamahata <isaku.yamahata@...el.com>, "Michael
Roth" <michael.roth@....com>, Yu Zhang <yu.c.zhang@...ux.intel.com>, "Chao
Peng" <chao.p.peng@...ux.intel.com>, Fuad Tabba <tabba@...gle.com>, "David
Matlack" <dmatlack@...gle.com>
Subject: Re: [PATCH 12/16] KVM: x86/mmu: Move slot checks from
__kvm_faultin_pfn() to kvm_faultin_pfn()
Ditto for accesses to KVM internal memslots from L2, which
> KVM also treats as emulated MMIO.
Nit:
This is not accurate anymore due to your previous patch ("KVM: x86/mmu:
Don't force emulation of L2 accesses to non-APIC internal slots").
>
> More importantly, this will allow for future cleanup by having the
> "no memslot" case bail from kvm_faultin_pfn() very early on.
>
> Go to rather extreme and gross lengths to make the change a glorified
> nop, e.g. call into __kvm_faultin_pfn() even when there is no slot, as the
> related code is very subtle. E.g. fault->slot can be nullified if it
> points at the APIC access page, some flows in KVM x86 expect fault->pfn
> to be KVM_PFN_NOSLOT, while others check only fault->slot, etc.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Feel free to add:
Reviewed-by: Kai Huang <kai.huang@...el.com>
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