linux-kernel - Re: [PATCH v2 8/8] KVM: x86: Add checks for reserved-to-zero Hyper-V hypercall fields

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Message-ID: <YagrxIknF9DX8l8L@google.com>
Date:   Thu, 2 Dec 2021 02:13:24 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ajay Garg <ajaygargnsit@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 8/8] KVM: x86: Add checks for reserved-to-zero Hyper-V
 hypercall fields

On Mon, Nov 01, 2021, Vitaly Kuznetsov wrote:
> Sean Christopherson <seanjc@...gle.com> writes:
> 
> > Add checks for the three fields in Hyper-V's hypercall params that must
> > be zero.  Per the TLFS, HV_STATUS_INVALID_HYPERCALL_INPUT is returned if
> > "A reserved bit in the specified hypercall input value is non-zero."
> >
> > Note, the TLFS has an off-by-one bug for the last reserved field, which
> > it defines as being bits 64:60.  The same section states "The input field
> > 64-bit value called a hypercall input value.", i.e. bit 64 doesn't
> > exist.
> 
> This version are you looking at? I can't see this issue in 6.0b

It's the web-based documentation, the 6.0b PDF indeed does not have the same bug.

https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface#hypercall-inputs