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Subject[PATCH 04/10] KVM: Document Memory ROE
Date
ROE version documented here is implemented in the next 2 patches
Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman@mena.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
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