linux-kernel - [PATCH] arm64: fix documentation on kernel pages mappings to HYP VA

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Message-Id: <20170913180830.8608-1-ynorov@caviumnetworks.com>
Date:   Wed, 13 Sep 2017 21:08:30 +0300
From:   Yury Norov <ynorov@...iumnetworks.com>
To:     Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     Yury Norov <ynorov@...iumnetworks.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org
Subject: [PATCH] arm64: fix documentation on kernel pages mappings to HYP VA

The Documentation/arm64/memory.txt says:
When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
offset from the kernel VA (top 24bits of the kernel VA set to zero):

In fact, kernel addresses are transleted to HYP with kern_hyp_va macro,
which has more options, and none of them assumes clearing of top 24bits
of the kernel VA.

Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
---
 Documentation/arm64/memory.txt | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
index d7273a5f6456..c39895d7e3a2 100644
--- a/Documentation/arm64/memory.txt
+++ b/Documentation/arm64/memory.txt
@@ -86,9 +86,12 @@ Translation table lookup with 64KB pages:
  +-------------------------------------------------> [63] TTBR0/1
 
 
-When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
-offset from the kernel VA (top 24bits of the kernel VA set to zero):
-
-Start			End			Size		Use
------------------------------------------------------------------------
-0000004000000000	0000007fffffffff	 256GB		kernel objects mapped in HYP
+When using KVM without Virtualization Host Extensions, the hypervisor maps
+kernel pages in EL2, at a fixed offset from the kernel VA. Namely, top 16
+or 25 bits of the kernel VA set to zero depending on ARM64_VA_BITS_48 or
+ARM64_VA_BITS_39 config option selected; or top 17 or 26 bits of the kernel
+VA set to zero if CPU has Reduced HYP mapping offset capability. See
+kern_hyp_va macro.
+
+When using KVM with Virtualization Host Extensions, no additional mappings
+created as host kernel already operates in EL2.
-- 
2.11.0