linux-kernel - RE: [PATCH] KVM: x86: handle wrap around 32-bit address space

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Message-ID: <c3ac5f4c9e3a412cb57ea02df19dd2d2@AcuMS.aculab.com>
Date:   Wed, 29 Apr 2020 08:50:21 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Jim Mattson' <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "Sean Christopherson" <sean.j.christopherson@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "everdox@...il.com" <everdox@...il.com>
Subject: RE: [PATCH] KVM: x86: handle wrap around 32-bit address space

From: Jim Mattson
> Sent: 28 April 2020 01:29
> On Mon, Apr 27, 2020 at 9:59 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
> >
> > KVM is not handling the case where EIP wraps around the 32-bit address
> > space (that is, outside long mode).  This is needed both in vmx.c
> > and in emulate.c.  SVM with NRIPS is okay, but it can still print
> > an error to dmesg due to integer overflow.
...
> > +               if (unlikely(((rip ^ orig_rip) >> 31) == 3) && !is_64_bit_mode(vcpu))

Isn't the more obvious:
	if (((rip ^ orig_rip) & 1ull << 32) ...
equivalent?

	David

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