LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Oliver Upton <oupton@google.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Peter Shier <pshier@google.com>
Subject: Re: [PATCH] KVM: nVMX: Use vmx_need_pf_intercept() when deciding if L0 wants a #PF
Date: Wed, 11 Aug 2021 22:55:44 -0700	[thread overview]
Message-ID: <CAOQ_QsiixM-D8n0_WNsMu5OVo0ip_qzE5nvoUSej9r+pFy40tw@mail.gmail.com> (raw)
In-Reply-To: <20210812045615.3167686-1-seanjc@google.com>

On Wed, Aug 11, 2021 at 9:56 PM Sean Christopherson <seanjc@google.com> wrote:
>
> Use vmx_need_pf_intercept() when determining if L0 wants to handle a #PF
> in L2 or if the VM-Exit should be forwarded to L1.  The current logic fails
> to account for the case where #PF is intercepted to handle
> guest.MAXPHYADDR < host.MAXPHYADDR and ends up reflecting all #PFs into
> L1.  At best, L1 will complain and inject the #PF back into L2.  At
> worst, L1 will eat the unexpected fault and cause L2 to hang on infinite
> page faults.
>
> Note, while the bug was technically introduced by the commit that added
> support for the MAXPHYADDR madness, the shame is all on commit
> a0c134347baf ("KVM: VMX: introduce vmx_need_pf_intercept").
>
> Fixes: 1dbf5d68af6f ("KVM: VMX: Add guest physical address check in EPT violation and misconfig")
> Cc: stable@vger.kernel.org
> Cc: Peter Shier <pshier@google.com>
> Cc: Oliver Upton <oupton@google.com>
> Cc: Jim Mattson <jmattson@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Oliver Upton <oupton@google.com>

--
Thanks,
Oliver

> ---
>  arch/x86/kvm/vmx/nested.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index bc6327950657..8bcbe57b560f 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5830,7 +5830,8 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu,
>                 if (is_nmi(intr_info))
>                         return true;
>                 else if (is_page_fault(intr_info))
> -                       return vcpu->arch.apf.host_apf_flags || !enable_ept;
> +                       return vcpu->arch.apf.host_apf_flags ||
> +                              vmx_need_pf_intercept(vcpu);
>                 else if (is_debug(intr_info) &&
>                          vcpu->guest_debug &
>                          (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
> --
> 2.33.0.rc1.237.g0d66db33f3-goog
>

  reply	other threads:[~2021-08-12  5:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-12  4:56 Sean Christopherson
2021-08-12  5:55 ` Oliver Upton [this message]
2021-08-12 16:18 ` Paolo Bonzini

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAOQ_QsiixM-D8n0_WNsMu5OVo0ip_qzE5nvoUSej9r+pFy40tw@mail.gmail.com \
    --to=oupton@google.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pbonzini@redhat.com \
    --cc=pshier@google.com \
    --cc=seanjc@google.com \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    --subject='Re: [PATCH] KVM: nVMX: Use vmx_need_pf_intercept() when deciding if L0 wants a #PF' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).