Messages in this thread | | | Date | Thu, 1 Dec 2022 23:00:13 +0100 | Subject | Re: [PATCH v2 21/50] KVM: MIPS: Hardcode callbacks to hardware virtualization extensions | From | Philippe Mathieu-Daudé <> |
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On 1/12/22 00:09, Sean Christopherson wrote: > Now that KVM no longer supports trap-and-emulate (see commit 45c7e8af4a5e > "MIPS: Remove KVM_TE support"), hardcode the MIPS callbacks to the > virtualization callbacks. > > Harcoding the callbacks eliminates the technically-unnecessary check on > non-NULL kvm_mips_callbacks in kvm_arch_init(). MIPS has never supported > multiple in-tree modules, i.e. barring an out-of-tree module, where > copying and renaming kvm.ko counts as "out-of-tree", KVM could never > encounter a non-NULL set of callbacks during module init. > > The callback check is also subtly broken, as it is not thread safe, > i.e. if there were multiple modules, loading both concurrently would > create a race between checking and setting kvm_mips_callbacks. > > Given that out-of-tree shenanigans are not the kernel's responsibility, > hardcode the callbacks to simplify the code. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/mips/include/asm/kvm_host.h | 2 +- > arch/mips/kvm/Makefile | 2 +- > arch/mips/kvm/callback.c | 14 -------------- > arch/mips/kvm/mips.c | 9 ++------- > arch/mips/kvm/vz.c | 7 ++++--- > 5 files changed, 8 insertions(+), 26 deletions(-) > delete mode 100644 arch/mips/kvm/callback.c > > diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h > index 28f0ba97db71..2803c9c21ef9 100644 > --- a/arch/mips/include/asm/kvm_host.h > +++ b/arch/mips/include/asm/kvm_host.h > @@ -758,7 +758,7 @@ struct kvm_mips_callbacks { > void (*vcpu_reenter)(struct kvm_vcpu *vcpu); > }; > extern struct kvm_mips_callbacks *kvm_mips_callbacks;
IIUC we could even constify this pointer.
Anyway, Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c > index af29490d9740..f0a6c245d1ff 100644 > --- a/arch/mips/kvm/mips.c > +++ b/arch/mips/kvm/mips.c > @@ -1012,17 +1012,12 @@ long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) > > int kvm_arch_init(void *opaque) > { > - if (kvm_mips_callbacks) { > - kvm_err("kvm: module already exists\n"); > - return -EEXIST; > - } > - > - return kvm_mips_emulation_init(&kvm_mips_callbacks); > + return kvm_mips_emulation_init(); > } > > void kvm_arch_exit(void) > { > - kvm_mips_callbacks = NULL; > + > } > > int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu, > diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c > index c706f5890a05..dafab003ea0d 100644 > --- a/arch/mips/kvm/vz.c > +++ b/arch/mips/kvm/vz.c > @@ -3304,7 +3304,10 @@ static struct kvm_mips_callbacks kvm_vz_callbacks = { > .vcpu_reenter = kvm_vz_vcpu_reenter, > }; > > -int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks) > +/* FIXME: Get rid of the callbacks now that trap-and-emulate is gone. */ > +struct kvm_mips_callbacks *kvm_mips_callbacks = &kvm_vz_callbacks;
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