Patch "KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-arm64-make-vcpu_cp1x-work-on-big-endian-hosts.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 3204be4109ad681523e3461ce64454c79278450a Mon Sep 17 00:00:00 2001

From: Marc Zyngier <[email protected]>
Date: Tue, 9 Jun 2020 08:40:35 +0100
Subject: KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts

From: Marc Zyngier <[email protected]>

commit 3204be4109ad681523e3461ce64454c79278450a upstream.

AArch32 CP1x registers are overlayed on their AArch64 counterparts in the vcpu struct. This leads to an interesting problem as they are stored in their CPU-local format, and thus a CP1x register doesn't "hit" the lower 32bit portion of the AArch64 register on a BE host.

To workaround this unfortunate situation, introduce a bias trick in the vcpu_cp1x() accessors which picks the correct half of the 64bit register.

Cc [email protected]

Reported-by James Morse <[email protected]>

Tested-by James Morse <[email protected]>

Acked-by James Morse <[email protected]>

Signed-off-by Marc Zyngier <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
  arch/arm64/include/asm/kvm_host.h |    6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

arch/arm64/include/asm/kvm_host.h +4 -2

@@ -178,8 +178,10 @@ struct kvm_vcpu_arch {
   * CP14 and CP15 live in the same array, as they are backed by the
   * same system registers.
   */
-#define vcpu_cp14(v,r)		((v)->arch.ctxt.copro[(r)])
-#define vcpu_cp15(v,r)		((v)->arch.ctxt.copro[(r)])
+#define CPx_BIAS		IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)
+
+#define vcpu_cp14(v,r)		((v)->arch.ctxt.copro[(r) ^ CPx_BIAS])
+#define vcpu_cp15(v,r)		((v)->arch.ctxt.copro[(r) ^ CPx_BIAS])
 
  #ifdef CONFIG_CPU_BIG_ENDIAN
  #define vcpu_cp15_64_high(v,r)	vcpu_cp15((v),(r))

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/kvm-arm64-make-vcpu_cp1x-work-on-big-endian-hosts.patch

.

Hi,

Not familiar with kvm. And I have a question about this patch. Maybe backport this patch 3204be4109ad("KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts") without 52f6c4f02164 ("KVM: arm64: Change 32-bit handling of VM system registers") seems not right?

Hi,

Not familiar with kvm. And I have a question about this patch. Maybe backport this patch 3204be4109ad("KVM: arm64: Make vcpu_cp1x() work on Big Endian hosts") without 52f6c4f02164 ("KVM: arm64: Change 32-bit handling of VM system registers") seems not right?