| Message ID | 20221130230934.1014142-22-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Rework kvm_init() and hardware enabling | expand |
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;
On Thu, Dec 01, 2022, Philippe Mathieu-Daudé wrote: > 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. Good point. Protecting the pointer itself is a bit gross, but it is a nice stopgap until the callbacks are gone. I'll fold this in. Thanks! extern const struct kvm_mips_callbacks * const kvm_mips_callbacks;
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; -int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks); +int kvm_mips_emulation_init(void); /* Debug: dump vcpu state */ int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu); diff --git a/arch/mips/kvm/Makefile b/arch/mips/kvm/Makefile index 21ff75bcdbc4..805aeea2166e 100644 --- a/arch/mips/kvm/Makefile +++ b/arch/mips/kvm/Makefile @@ -17,4 +17,4 @@ kvm-$(CONFIG_CPU_LOONGSON64) += loongson_ipi.o kvm-y += vz.o obj-$(CONFIG_KVM) += kvm.o -obj-y += callback.o tlb.o +obj-y += tlb.o diff --git a/arch/mips/kvm/callback.c b/arch/mips/kvm/callback.c deleted file mode 100644 index d88aa2173fb0..000000000000 --- a/arch/mips/kvm/callback.c +++ /dev/null @@ -1,14 +0,0 @@ -/* - * This file is subject to the terms and conditions of the GNU General Public - * License. See the file "COPYING" in the main directory of this archive - * for more details. - * - * Copyright (C) 2012 MIPS Technologies, Inc. All rights reserved. - * Authors: Yann Le Du <ledu@kymasys.com> - */ - -#include <linux/export.h> -#include <linux/kvm_host.h> - -struct kvm_mips_callbacks *kvm_mips_callbacks; -EXPORT_SYMBOL_GPL(kvm_mips_callbacks); 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; + +int kvm_mips_emulation_init(void) { if (!cpu_has_vz) return -ENODEV; @@ -3318,7 +3321,5 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks) return -ENODEV; pr_info("Starting KVM with MIPS VZ extensions\n"); - - *install_callbacks = &kvm_vz_callbacks; return 0; }
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