Messages in this thread | | | Subject | Re: [PATCH v2 3/9] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl | From | Dov Murik <> | Date | Sun, 6 Dec 2020 13:02:47 +0200 |
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On 01/12/2020 2:47, Ashish Kalra wrote: > From: Brijesh Singh <brijesh.singh@amd.com> > > The ioctl can be used to retrieve page encryption bitmap for a given > gfn range. > > Return the correct bitmap as per the number of pages being requested > by the user. Ensure that we only copy bmap->num_pages bytes in the > userspace buffer, if bmap->num_pages is not byte aligned we read > the trailing bits from the userspace and copy those bits as is.
I think you meant to say "Ensure that we only copy bmap->num_pages *bits* in the userspace buffer". But maybe I'm missed something.
> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > Cc: Joerg Roedel <joro@8bytes.org> > Cc: Borislav Petkov <bp@suse.de> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: x86@kernel.org > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com> > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> > --- > Documentation/virt/kvm/api.rst | 27 +++++++++++++ > arch/x86/include/asm/kvm_host.h | 2 + > arch/x86/kvm/svm/sev.c | 70 +++++++++++++++++++++++++++++++++ > arch/x86/kvm/svm/svm.c | 1 + > arch/x86/kvm/svm/svm.h | 1 + > arch/x86/kvm/x86.c | 12 ++++++ > include/uapi/linux/kvm.h | 12 ++++++ > 7 files changed, 125 insertions(+) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 70254eaa5229..ae410f4332ab 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -4671,6 +4671,33 @@ This ioctl resets VCPU registers and control structures according to > the clear cpu reset definition in the POP. However, the cpu is not put > into ESA mode. This reset is a superset of the initial reset. > > +4.125 KVM_GET_PAGE_ENC_BITMAP (vm ioctl) > +--------------------------------------- > + > +:Capability: basic > +:Architectures: x86 > +:Type: vm ioctl > +:Parameters: struct kvm_page_enc_bitmap (in/out) > +:Returns: 0 on success, -1 on error > + > +/* for KVM_GET_PAGE_ENC_BITMAP */ > +struct kvm_page_enc_bitmap { > + __u64 start_gfn; > + __u64 num_pages; > + union { > + void __user *enc_bitmap; /* one bit per page */ > + __u64 padding2; > + }; > +}; > + > +The encrypted VMs have the concept of private and shared pages. The private > +pages are encrypted with the guest-specific key, while the shared pages may > +be encrypted with the hypervisor key. The KVM_GET_PAGE_ENC_BITMAP can > +be used to get the bitmap indicating whether the guest page is private > +or shared. The bitmap can be used during the guest migration. If the page > +is private then the userspace need to use SEV migration commands to transmit > +the page. > + > > 4.125 KVM_S390_PV_COMMAND > ------------------------- > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index d035dc983a7a..8c2e40199ecb 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1284,6 +1284,8 @@ struct kvm_x86_ops { > void (*msr_filter_changed)(struct kvm_vcpu *vcpu); > int (*page_enc_status_hc)(struct kvm *kvm, unsigned long gpa, > unsigned long sz, unsigned long mode); > + int (*get_page_enc_bitmap)(struct kvm *kvm, > + struct kvm_page_enc_bitmap *bmap); > }; > > struct kvm_x86_nested_ops { > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 6b8bc1297f9c..a6586dd29767 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -1014,6 +1014,76 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa, > return 0; > } > > +int svm_get_page_enc_bitmap(struct kvm *kvm, > + struct kvm_page_enc_bitmap *bmap) > +{ > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > + unsigned long gfn_start, gfn_end; > + unsigned long sz, i, sz_bytes; > + unsigned long *bitmap; > + int ret, n; > + > + if (!sev_guest(kvm)) > + return -ENOTTY; > + > + gfn_start = bmap->start_gfn; > + gfn_end = gfn_start + bmap->num_pages; > + > + sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / BITS_PER_BYTE; > + bitmap = kmalloc(sz, GFP_KERNEL);
Maybe use bitmap_alloc which accepts size in bits (and corresponding bitmap_free)?
> + if (!bitmap) > + return -ENOMEM; > + > + /* by default all pages are marked encrypted */ > + memset(bitmap, 0xff, sz);
Maybe use bitmap_fill to clarify the intent?
> + > + mutex_lock(&kvm->lock); > + if (sev->page_enc_bmap) { > + i = gfn_start; > + for_each_clear_bit_from(i, sev->page_enc_bmap, > + min(sev->page_enc_bmap_size, gfn_end)) > + clear_bit(i - gfn_start, bitmap); > + } > + mutex_unlock(&kvm->lock); > + > + ret = -EFAULT; > + > + n = bmap->num_pages % BITS_PER_BYTE; > + sz_bytes = ALIGN(bmap->num_pages, BITS_PER_BYTE) / BITS_PER_BYTE;
Maybe clearer:
sz_bytes = BITS_TO_BYTES(bmap->num_pages);
> + > + /* > + * Return the correct bitmap as per the number of pages being > + * requested by the user. Ensure that we only copy bmap->num_pages > + * bytes in the userspace buffer, if bmap->num_pages is not byte > + * aligned we read the trailing bits from the userspace and copy > + * those bits as is. > + */
(see my comment on the commit message above.)
> + > + if (n) { > + unsigned char *bitmap_kernel = (unsigned char *)bitmap; > + unsigned char bitmap_user; > + unsigned long offset, mask; > + > + offset = bmap->num_pages / BITS_PER_BYTE; > + if (copy_from_user(&bitmap_user, bmap->enc_bitmap + offset, > + sizeof(unsigned char))) > + goto out; > + > + mask = GENMASK(n - 1, 0); > + bitmap_user &= ~mask; > + bitmap_kernel[offset] &= mask; > + bitmap_kernel[offset] |= bitmap_user; > + } > + > + if (copy_to_user(bmap->enc_bitmap, bitmap, sz_bytes)) > + goto out; > + > + ret = 0; > +out: > + kfree(bitmap); > + return ret; > +} > + > int svm_mem_enc_op(struct kvm *kvm, void __user *argp) > { > struct kvm_sev_cmd sev_cmd; > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 7122ea5f7c47..bff89cab3ed0 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -4314,6 +4314,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { > .msr_filter_changed = svm_msr_filter_changed, > > .page_enc_status_hc = svm_page_enc_status_hc, > + .get_page_enc_bitmap = svm_get_page_enc_bitmap, > }; > > static struct kvm_x86_init_ops svm_init_ops __initdata = { > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 0103a23ca174..4ce73f1034b9 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -413,6 +413,7 @@ int nested_svm_exit_special(struct vcpu_svm *svm); > void sync_nested_vmcb_control(struct vcpu_svm *svm); > int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa, > unsigned long npages, unsigned long enc); > +int svm_get_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap *bmap); > > extern struct kvm_x86_nested_ops svm_nested_ops; > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 3afc78f18f69..d3cb95a4dd55 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5695,6 +5695,18 @@ long kvm_arch_vm_ioctl(struct file *filp, > case KVM_X86_SET_MSR_FILTER: > r = kvm_vm_ioctl_set_msr_filter(kvm, argp); > break; > + case KVM_GET_PAGE_ENC_BITMAP: { > + struct kvm_page_enc_bitmap bitmap; > + > + r = -EFAULT; > + if (copy_from_user(&bitmap, argp, sizeof(bitmap))) > + goto out; > + > + r = -ENOTTY; > + if (kvm_x86_ops.get_page_enc_bitmap) > + r = kvm_x86_ops.get_page_enc_bitmap(kvm, &bitmap); > + break; > + } > default: > r = -ENOTTY; > } > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 886802b8ffba..d0b9171bdb03 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -532,6 +532,16 @@ struct kvm_dirty_log { > }; > }; > > +/* for KVM_GET_PAGE_ENC_BITMAP */ > +struct kvm_page_enc_bitmap { > + __u64 start_gfn; > + __u64 num_pages; > + union { > + void __user *enc_bitmap; /* one bit per page */ > + __u64 padding2; > + }; > +}; > + > /* for KVM_CLEAR_DIRTY_LOG */ > struct kvm_clear_dirty_log { > __u32 slot; > @@ -1563,6 +1573,8 @@ struct kvm_pv_cmd { > /* Available with KVM_CAP_DIRTY_LOG_RING */ > #define KVM_RESET_DIRTY_RINGS _IO(KVMIO, 0xc7) > > +#define KVM_GET_PAGE_ENC_BITMAP _IOW(KVMIO, 0xc6, struct kvm_page_enc_bitmap)
I see that kvm/next already defines ioctls numbered 0xc6 and 0xc7. Wouldn't these new ioctls (KVM_GET_PAGE_ENC_BITMAP, KVM_SET_PAGE_ENC_BITMAP) collide?
> + > /* Secure Encrypted Virtualization command */ > enum sev_cmd_id { > /* Guest initialization commands */ >
-Dov
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