| Message ID | 1599734031-28746-1-git-send-email-chenhc@lemote.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: MIPS: Change the definition of kvm type | expand |
On 11/09/2020 19.22, Paolo Bonzini wrote: > On 10/09/20 12:33, Huacai Chen wrote: >> 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. > > I'm a bit wary to do that. However it's not an issue for QEMU since it > generally updates the kernel headers. Are there any other userspace programs beside QEMU that use KVM on MIPS? If there aren't any other serious userspace programs, I think we should go ahead with this patch here. Otherwise, what are the other programs that could be affected? Thomas
On 19/09/20 11:18, Thomas Huth wrote: >>> >>> 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. >> I'm a bit wary to do that. However it's not an issue for QEMU since it >> generally updates the kernel headers. > Are there any other userspace programs beside QEMU that use KVM on MIPS? > If there aren't any other serious userspace programs, I think we should > go ahead with this patch here. Otherwise, what are the other programs > that could be affected? kvmtool (aka lkvm) I guess. I don't know if it is affected but I wouldn't be worried. Paolo
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index d7ba3f9..9efeb67 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -138,6 +138,8 @@ extern void kvm_init_loongson_ipi(struct kvm *kvm); 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 29ba8e8..cfc1ae2 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -790,9 +790,10 @@ 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
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. Cc: stable@vger.kernel.org Signed-off-by: Huacai Chen <chenhc@lemote.com> --- arch/mips/kvm/mips.c | 2 ++ include/uapi/linux/kvm.h | 5 +++-- 2 files changed, 5 insertions(+), 2 deletions(-)