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Date: Thu, 19 Jul 2018 18:11:11 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Ahmed Abd El Mawgood <ahmedsoliman0x666@...il.com>, kvm@...r.kernel.org,
 Kernel Hardening <kernel-hardening@...ts.openwall.com>,
 virtualization@...ts.linux-foundation.org, linux-doc@...r.kernel.org,
 x86@...nel.org
Cc: Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
 nathan Corbet <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
 Kees Cook <keescook@...omium.org>, Ard Biesheuvel
 <ard.biesheuvel@...aro.org>, David Hildenbrand <david@...hat.com>,
 Boris Lukashev <blukashev@...pervictus.com>,
 David Vrabel <david.vrabel@...anix.com>, nigel.edwards@....com,
 Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 1/3] [RFC V3] KVM: X86: Memory ROE documentation

On 07/19/2018 02:38 PM, Ahmed Abd El Mawgood wrote:

>  Documentation/virtual/kvm/hypercalls.txt | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
> index a890529c63ed..a9db68adb7c9 100644
> --- a/Documentation/virtual/kvm/hypercalls.txt
> +++ b/Documentation/virtual/kvm/hypercalls.txt
> @@ -121,3 +121,17 @@ compute the CLOCK_REALTIME for its clock, at the same instant.
>  
>  Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
>  or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
> +
> +7. KVM_HC_HMROE
> +----------------
> +Architecture: x86
> +Status: active
> +Purpose: Hypercall used to apply Read-Only Enforcement to guest pages
> +Usage:
> +     a0: start address of page that should be protected.

Is this done one page per call?  No grouping, no multiple pages?

> +
> +This hypercall lets a guest kernel to have part of its read/write memory

                  lets a guest kernel have part of

> +converted into read-only.  This action is irreversible. KVM_HC_HMROE can
> +not be triggered from guest Ring 3 (user mode). The reason is that user
> +mode malicious software can make use of it enforce read only protection on

                               make use of it to enforce

> +an arbitrary memory page thus crashing the kernel.
> 


-- 
~Randy

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