Messages in this thread | | | Subject | Re: [PATCH v2 1/2] KVM: Refactor kvm_arch_vcpu_fault() to return a struct page pointer | From | Christian Borntraeger <> | Date | Mon, 23 Aug 2021 16:12:40 +0200 |
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On 12.08.21 11:04, David Hildenbrand wrote: > On 12.08.21 06:02, Hou Wenlong wrote: >> From: Sean Christopherson <seanjc@google.com> >> >> Refactor kvm_arch_vcpu_fault() to return 'struct page *' instead of >> 'vm_fault_t' to simplify architecture specific implementations that do >> more than return SIGBUS. Currently this only applies to s390, but a >> future patch will move x86's pio_data handling into x86 where it belongs. >> >> No functional changed intended. >> >> Cc: Hou Wenlong <houwenlong93@linux.alibaba.com> >> Signed-off-by: Sean Christopherson <seanjc@google.com> >> Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com> >> --- >> arch/arm64/kvm/arm.c | 4 ++-- >> arch/mips/kvm/mips.c | 4 ++-- >> arch/powerpc/kvm/powerpc.c | 4 ++-- >> arch/s390/kvm/kvm-s390.c | 12 ++++-------- >> arch/x86/kvm/x86.c | 4 ++-- >> include/linux/kvm_host.h | 2 +- >> virt/kvm/kvm_main.c | 5 ++++- >> 7 files changed, 17 insertions(+), 18 deletions(-) >> >> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c >> index e9a2b8f27792..83f4ffe3e4f2 100644 >> --- a/arch/arm64/kvm/arm.c >> +++ b/arch/arm64/kvm/arm.c >> @@ -161,9 +161,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) >> return ret; >> } >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> { >> - return VM_FAULT_SIGBUS; >> + return NULL; >> } >> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c >> index af9dd029a4e1..ae79874e6fd2 100644 >> --- a/arch/mips/kvm/mips.c >> +++ b/arch/mips/kvm/mips.c >> @@ -1053,9 +1053,9 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) >> return -ENOIOCTLCMD; >> } >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> { >> - return VM_FAULT_SIGBUS; >> + return NULL; >> } >> int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c >> index be33b5321a76..b9c21f9ab784 100644 >> --- a/arch/powerpc/kvm/powerpc.c >> +++ b/arch/powerpc/kvm/powerpc.c >> @@ -2090,9 +2090,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp, >> return r; >> } >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> { >> - return VM_FAULT_SIGBUS; >> + return NULL; >> } >> static int kvm_vm_ioctl_get_pvinfo(struct kvm_ppc_pvinfo *pvinfo) >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index 02574d7b3612..e1b69833e228 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -4979,17 +4979,13 @@ long kvm_arch_vcpu_ioctl(struct file *filp, >> return r; >> } >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> { >> #ifdef CONFIG_KVM_S390_UCONTROL >> - if ((vmf->pgoff == KVM_S390_SIE_PAGE_OFFSET) >> - && (kvm_is_ucontrol(vcpu->kvm))) { >> - vmf->page = virt_to_page(vcpu->arch.sie_block); >> - get_page(vmf->page); >> - return 0; >> - } >> + if (vmf->pgoff == KVM_S390_SIE_PAGE_OFFSET && kvm_is_ucontrol(vcpu->kvm)) >> + return virt_to_page(vcpu->arch.sie_block); >> #endif >> - return VM_FAULT_SIGBUS; >> + return NULL; >> } >> /* Section: memory related */ >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 3cedc7cc132a..1e3bbe5cd33a 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -5347,9 +5347,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp, >> return r; >> } >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf) >> { >> - return VM_FAULT_SIGBUS; >> + return NULL; >> } >> static int kvm_vm_ioctl_set_tss_addr(struct kvm *kvm, unsigned long addr) >> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h >> index 492d183dd7d0..a949de534722 100644 >> --- a/include/linux/kvm_host.h >> +++ b/include/linux/kvm_host.h >> @@ -995,7 +995,7 @@ long kvm_arch_dev_ioctl(struct file *filp, >> unsigned int ioctl, unsigned long arg); >> long kvm_arch_vcpu_ioctl(struct file *filp, >> unsigned int ioctl, unsigned long arg); >> -vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf); >> +struct page *kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf); >> int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext); >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index 30d322519253..f7d21418971b 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -3448,7 +3448,10 @@ static vm_fault_t kvm_vcpu_fault(struct vm_fault *vmf) >> &vcpu->dirty_ring, >> vmf->pgoff - KVM_DIRTY_LOG_PAGE_OFFSET); >> else >> - return kvm_arch_vcpu_fault(vcpu, vmf); >> + page = kvm_arch_vcpu_fault(vcpu, vmf); >> + if (!page) >> + return VM_FAULT_SIGBUS; >> + >> get_page(page); >> vmf->page = page; >> return 0; >> > > Reviewed-by: David Hildenbrand <david@redhat.com> > > But at the same time I wonder if we should just get rid of CONFIG_KVM_S390_UCONTROL and consequently kvm_arch_vcpu_fault(). > > > In practice CONFIG_KVM_S390_UCONTROL, is never enabled in any reasonable kernel build and consequently it's never tested; further, exposing the sie_block to user space allows user space to generate random SIE validity intercepts. > > CONFIG_KVM_S390_UCONTROL feels like something that should just be maintained out of tree by someone who really needs to hack deep into hw virtualization for testing purposes etc.
I recently talked to the ucontrol users and they will look into selftests.
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