From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Santosh Shukla <santosh.shukla@amd.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI
Date: Thu, 21 Jul 2022 16:25:40 +0000 [thread overview]
Message-ID: <Ytl+BGei3zUlHY6l@google.com> (raw)
In-Reply-To: <23f156d46033a6434591186b0a7bcce3d8a138d1.camel@redhat.com>
On Thu, Jul 21, 2022, Maxim Levitsky wrote:
> On Thu, 2022-07-21 at 16:08 +0000, Sean Christopherson wrote:
> > So we have a poor man's NMI-window exiting.
>
> Yep, we also intercept IRET for the same purpose, and RSM interception
> is also a place the NMI are evaluated.
>
> We only single step over the IRET, because NMIs are unmasked _after_ the IRET
> retires.
Heh, check out this blurb from Intel's SDM:
An execution of the IRET instruction unblocks NMIs even if the instruction
causes a fault. For example, if the IRET instruction executes with EFLAGS.VM = 1
and IOPL of less than 3, a general-protection exception is generated (see
Section 20.2.7, “Sensitive Instructions”). In such a case, NMIs are unmasked
before the exception handler is invoked.
Not that I want to try and handle that in KVM if AMD follows suit, I simply find
it amusing how messy this all is. A true NMI-window exit would have been nice...
next prev parent reply other threads:[~2022-07-21 16:25 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-09 13:42 [PATCHv2 0/7] Virtual NMI feature Santosh Shukla
2022-07-09 13:42 ` [PATCHv2 1/7] x86/cpu: Add CPUID feature bit for VNMI Santosh Shukla
2022-07-09 13:42 ` [PATCHv2 2/7] KVM: SVM: Add VNMI bit definition Santosh Shukla
2022-07-09 13:42 ` [PATCHv2 3/7] KVM: SVM: Add VNMI support in get/set_nmi_mask Santosh Shukla
2022-07-10 16:15 ` Maxim Levitsky
2022-07-21 9:34 ` Shukla, Santosh
2022-07-21 12:01 ` Maxim Levitsky
2022-07-21 13:12 ` Shukla, Santosh
2022-07-21 15:48 ` Maxim Levitsky
2022-07-09 13:42 ` [PATCHv2 4/7] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI Santosh Shukla
2022-07-20 21:54 ` Sean Christopherson
2022-07-21 12:05 ` Maxim Levitsky
2022-07-21 14:59 ` Sean Christopherson
2022-07-21 15:31 ` Maxim Levitsky
2022-07-21 16:08 ` Sean Christopherson
2022-07-21 16:17 ` Maxim Levitsky
2022-07-21 16:25 ` Sean Christopherson [this message]
2022-07-29 5:51 ` Shukla, Santosh
2022-07-29 14:41 ` Sean Christopherson
2022-08-04 9:51 ` Shukla, Santosh
2022-07-09 13:42 ` [PATCHv2 5/7] KVM: SVM: Add VNMI support in inject_nmi Santosh Shukla
2022-07-20 21:41 ` Sean Christopherson
2022-07-20 22:46 ` Jim Mattson
2022-07-20 23:04 ` Sean Christopherson
2022-07-29 6:06 ` Shukla, Santosh
2022-07-29 13:53 ` Sean Christopherson
2022-07-29 13:55 ` Shukla, Santosh
2022-07-09 13:42 ` [PATCHv2 6/7] KVM: nSVM: implement nested VNMI Santosh Shukla
2022-07-09 13:42 ` [PATCHv2 7/7] KVM: SVM: Enable VNMI feature Santosh Shukla
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