From: Jim Mattson <jmattson@google.com>
To: kvm list <kvm@vger.kernel.org>
Subject: What's with all of the hardcoded instruction lengths in svm.c?
Date: Wed, 12 Jun 2019 13:17:33 -0700 [thread overview]
Message-ID: <CALMp9eQ4k71ox=0xQKM+CfOkFe6Vqp+0znJ3Ju4ZmyL9fgjm=w@mail.gmail.com> (raw)
Take the following code in rdmsr_interception, for example.
svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
Yes, the canonical rdmsr instruction is two bytes. However, there is
nothing in the architectural specification prohibiting useless or
redundant prefixes. So, for instance, 65 66 67 67 67 0f 32 is a
perfectly valid 7-byte rdmsr instruction.
It looks like this code was checked in with commit 6aa8b732ca01c
("kvm: userspace interface"), with nary a word of explanation.
next reply other threads:[~2019-06-12 20:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-12 20:17 Jim Mattson [this message]
2019-06-13 13:55 ` What's with all of the hardcoded instruction lengths in svm.c? Vitaly Kuznetsov
2019-06-13 16:08 ` Jim Mattson
2019-06-14 17:01 ` Vitaly Kuznetsov
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