linux-kernel - Re: [PATCH 2/4] KVM: nSVM: propagate the NPF EXITINFO to the guest

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Message-ID: <5405F7E1.1090505@redhat.com>
Date:	Tue, 02 Sep 2014 19:01:21 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Joerg Roedel <jroedel@...e.de>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org, agraf@...e.de,
	valentine.sinitsyn@...il.com, jan.kiszka@...mens.com,
	gleb@...udius-systems.com, avi@...udius-systems.com
Subject: Re: [PATCH 2/4] KVM: nSVM: propagate the NPF EXITINFO to the guest

Il 02/09/2014 18:46, Paolo Bonzini ha scritto:
>> > How about an io-port emulated on
>> > L1 but passed through to L2 by the nested hypervisor. On emulation of
>> > INS or OUTS, KVM would need to read/write to an L2 address space,
> It would need to read/write to *L1* (that's where the VMCB's IOIO map
> lies), which could result into a regular page fault injected into L1.

Nevermind, the VMCB's IO bitmap is a guest physical address.  I see what
you mean now.  nested_svm_intercept_ioio would return NESTED_EXIT_HOST
and proceed to emulate the read/write.  This could indeed cause a NPF.
For now I'll remove the WARN_ON.

Paolo
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