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Subject[PATCH 5.4 27/72] KVM: MIPS: Change the definition of kvm type
Date
From: Huacai Chen <chenhc@lemote.com>

[ Upstream commit 15e9e35cd1dec2bc138464de6bf8ef828df19235 ]

MIPS defines two kvm types:

#define KVM_VM_MIPS_TE 0
#define KVM_VM_MIPS_VZ 1

In Documentation/virt/kvm/api.rst it is said that "You probably want to
use 0 as machine type", which implies that type 0 be the "automatic" or
"default" type. And, in user-space libvirt use the null-machine (with
type 0) to detect the kvm capability, which returns "KVM not supported"
on a VZ platform.

I try to fix it in QEMU but it is ugly:
https://lists.nongnu.org/archive/html/qemu-devel/2020-08/msg05629.html

And Thomas Huth suggests me to change the definition of kvm type:
https://lists.nongnu.org/archive/html/qemu-devel/2020-09/msg03281.html

So I define like this:

#define KVM_VM_MIPS_AUTO 0
#define KVM_VM_MIPS_VZ 1
#define KVM_VM_MIPS_TE 2

Since VZ and TE cannot co-exists, using type 0 on a TE platform will
still return success (so old user-space tools have no problems on new
kernels); the advantage is that using type 0 on a VZ platform will not
return failure. So, the only problem is "new user-space tools use type
2 on old kernels", but if we treat this as a kernel bug, we can backport
this patch to old stable kernels.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Message-Id: <1599734031-28746-1-git-send-email-chenhc@lemote.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/mips/kvm/mips.c | 2 ++
include/uapi/linux/kvm.h | 5 +++--
2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 1109924560d8c..b22a3565e1330 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -131,6 +131,8 @@ int kvm_arch_check_processor_compat(void)
int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
{
switch (type) {
+ case KVM_VM_MIPS_AUTO:
+ break;
#ifdef CONFIG_KVM_MIPS_VZ
case KVM_VM_MIPS_VZ:
#else
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index e735bc4075dc7..1b6b8e05868dd 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -768,9 +768,10 @@ struct kvm_ppc_resize_hpt {
#define KVM_VM_PPC_HV 1
#define KVM_VM_PPC_PR 2

-/* on MIPS, 0 forces trap & emulate, 1 forces VZ ASE */
-#define KVM_VM_MIPS_TE 0
+/* on MIPS, 0 indicates auto, 1 forces VZ ASE, 2 forces trap & emulate */
+#define KVM_VM_MIPS_AUTO 0
#define KVM_VM_MIPS_VZ 1
+#define KVM_VM_MIPS_TE 2

#define KVM_S390_SIE_PAGE_OFFSET 1

--
2.25.1


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