linux-kernel - Re: [PATCH v19 018/130] KVM: x86/mmu: Assume guest MMIOs are shared

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Date: Mon, 25 Mar 2024 23:41:56 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Yamahata,
 Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "Gao, Chao" <chao.gao@...el.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>,
	"Huang, Kai" <kai.huang@...el.com>, "Chen, Bo2" <chen.bo@...el.com>,
	"sagis@...gle.com" <sagis@...gle.com>, "isaku.yamahata@...il.com"
	<isaku.yamahata@...il.com>, "Aktas, Erdem" <erdemaktas@...gle.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: Re: [PATCH v19 018/130] KVM: x86/mmu: Assume guest MMIOs are shared

On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@...el.com wrote:
> From: Chao Gao <chao.gao@...el.com>
> 
> TODO: Drop this patch once the common patch is merged.

What is this TODO talking about?

> 
> When memory slot isn't found for kvm page fault, handle it as MMIO.
> 
> The guest of TDX_VM, SNP_VM, or SW_PROTECTED_VM don't necessarily convert
> the virtual MMIO range to shared before accessing it.  When the guest tries
> to access the virtual device's MMIO without any private/shared conversion,
> An NPT fault or EPT violation is raised first to find private-shared
> mismatch.  Don't raise KVM_EXIT_MEMORY_FAULT, fall back to KVM_PFN_NOLSLOT.

If this is general KVM_X86_SW_PROTECTED_VM behavior, can we pull it out of the TDX series?

> 
> Signed-off-by: Chao Gao <chao.gao@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---