linux-kernel - Re: [PATCH 0/4] Process some MMIO-related errors without KVM exit

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Message-ID: <ZvGfnARMqZS0mkg-@google.com>
Date: Mon, 23 Sep 2024 10:04:28 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Ivan Orlov <iorlov@...zon.com>
Cc: hpa@...or.com, bp@...en8.de, dave.hansen@...ux.intel.com, mingo@...hat.com, 
	pbonzini@...hat.com, shuah@...nel.org, tglx@...utronix.de, 
	jalliste@...zon.com, nh-open-source@...zon.com, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 0/4] Process some MMIO-related errors without KVM exit

On Mon, Sep 23, 2024, Ivan Orlov wrote:
> Currently, KVM may return a variety of internal errors to VMM when
> accessing MMIO, and some of them could be gracefully handled on the KVM
> level instead. Moreover, some of the MMIO-related errors are handled
> differently in VMX in comparison with SVM, which produces certain
> inconsistency and should be fixed. This patch series introduces
> KVM-level handling for the following situations:
> 
> 1) Guest is accessing MMIO during event delivery: triple fault instead
> of internal error on VMX and infinite loop on SVM
> 
> 2) Guest fetches an instruction from MMIO: inject #UD and resume guest
> execution without internal error

No.  This is not architectural behavior.  It's not even remotely close to
architectural behavior.  KVM's behavior isn't great, but making up _guest visible_
behavior is not going to happen.