linux-kernel - [PATCH 04/10] KVM: Document Memory ROE

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Date:   Fri,  7 Dec 2018 14:47:57 +0200
From:   Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
To:     Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        hpa@...or.com, x86@...nel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ahmedsoliman0x666@...il.com, ovich00@...il.com,
        kernel-hardening@...ts.openwall.com, nigel.edwards@....com,
        Boris Lukashev <blukashev@...pervictus.com>,
        Igor Stoppa <igor.stoppa@...il.com>
Cc:     Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
Subject: [PATCH 04/10] KVM: Document Memory ROE

ROE version documented here is implemented in the next 2 patches
Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman@...a.vt.edu>
---
 Documentation/virtual/kvm/hypercalls.txt | 40 ++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
index da24c138c8..a31f316ce6 100644
--- a/Documentation/virtual/kvm/hypercalls.txt
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -141,3 +141,43 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
 corresponds to the APIC ID a2+1, and so on.
 
 Returns the number of CPUs to which the IPIs were delivered successfully.
+
+7. KVM_HC_ROE
+----------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to apply Read-Only Enforcement to guest memory and
+registers
+Usage 1:
+     a0: ROE_VERSION
+
+Returns non-signed number that represents the current version of ROE
+implementation current version.
+
+Usage 2:
+
+     a0: ROE_MPROTECT	(requires version >= 1)
+     a1: Start address aligned to page boundary.
+     a2: Number of pages to be protected.
+
+This configuration lets a guest kernel have part of its read/write memory
+converted into read-only.  This action is irreversible.
+Upon successful run, the number of pages protected is returned.
+
+Usage 3:
+     a0: ROE_MPROTECT_CHUNK	(requires version >= 2)
+     a1: Start address aligned to page boundary.
+     a2: Number of bytes to be protected.
+This configuration lets a guest kernel have part of its read/write memory
+converted into read-only with bytes granularity. ROE_MPROTECT_CHUNK is
+relatively slow compared to ROE_MPROTECT. This action is irreversible.
+Upon successful run, the number of bytes protected is returned.
+
+Error codes:
+	-KVM_ENOSYS: system call being triggered from ring 3 or it is not
+	implemented.
+	-EINVAL: error based on given parameters.
+
+Notes: KVM_HC_ROE can not be triggered from guest Ring 3 (user mode). The
+reason is that user mode malicious software can make use of it to enforce read
+only protection on an arbitrary memory page thus crashing the kernel.
-- 
2.19.2