| Message ID | 20210820155918.7518-27-brijesh.singh@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Part2,v5,01/45] x86/cpufeatures: Add SEV-SNP CPU feature | expand |
* Brijesh Singh (brijesh.singh@amd.com) wrote: > When SEV-SNP is enabled, the guest private pages are added in the RMP > table; while adding the pages, the rmp_make_private() unmaps the pages > from the direct map. If KSM attempts to access those unmapped pages then > it will trigger #PF (page-not-present). > > Encrypted guest pages cannot be shared between the process, so an > userspace should not mark the region mergeable but to be safe, mark the > process vma unmerable before adding the pages in the RMP table. ^^^^^^^^^ (and in the subject) -> unmergeable > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > arch/x86/kvm/svm/sev.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 4b126598b7aa..dcef0ae5f8e4 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -18,11 +18,13 @@ > #include <linux/processor.h> > #include <linux/trace_events.h> > #include <linux/sev.h> > +#include <linux/ksm.h> > #include <asm/fpu/internal.h> > > #include <asm/pkru.h> > #include <asm/trapnr.h> > #include <asm/sev.h> > +#include <asm/mman.h> > > #include "x86.h" > #include "svm.h" > @@ -1683,6 +1685,30 @@ static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) > return false; > } > > +static int snp_mark_unmergable(struct kvm *kvm, u64 start, u64 size) ^^^^^^^^^^ > +{ > + struct vm_area_struct *vma; > + u64 end = start + size; Do you need to worry about wrap there? (User supplied start/size?) Dave > + int ret; > + > + do { > + vma = find_vma_intersection(kvm->mm, start, end); > + if (!vma) { > + ret = -EINVAL; > + break; > + } > + > + ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > + MADV_UNMERGEABLE, &vma->vm_flags); > + if (ret) > + break; > + > + start = vma->vm_end; > + } while (end > vma->vm_end); > + > + return ret; > +} > + > static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > { > struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > @@ -1707,6 +1733,12 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > if (!is_hva_registered(kvm, params.uaddr, params.len)) > return -EINVAL; > > + mmap_write_lock(kvm->mm); > + ret = snp_mark_unmergable(kvm, params.uaddr, params.len); > + mmap_write_unlock(kvm->mm); > + if (ret) > + return -EFAULT; > + > /* > * The userspace memory is already locked so technically we don't > * need to lock it again. Later part of the function needs to know > -- > 2.17.1 > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 4b126598b7aa..dcef0ae5f8e4 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -18,11 +18,13 @@ #include <linux/processor.h> #include <linux/trace_events.h> #include <linux/sev.h> +#include <linux/ksm.h> #include <asm/fpu/internal.h> #include <asm/pkru.h> #include <asm/trapnr.h> #include <asm/sev.h> +#include <asm/mman.h> #include "x86.h" #include "svm.h" @@ -1683,6 +1685,30 @@ static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) return false; } +static int snp_mark_unmergable(struct kvm *kvm, u64 start, u64 size) +{ + struct vm_area_struct *vma; + u64 end = start + size; + int ret; + + do { + vma = find_vma_intersection(kvm->mm, start, end); + if (!vma) { + ret = -EINVAL; + break; + } + + ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, + MADV_UNMERGEABLE, &vma->vm_flags); + if (ret) + break; + + start = vma->vm_end; + } while (end > vma->vm_end); + + return ret; +} + static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) { struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; @@ -1707,6 +1733,12 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) if (!is_hva_registered(kvm, params.uaddr, params.len)) return -EINVAL; + mmap_write_lock(kvm->mm); + ret = snp_mark_unmergable(kvm, params.uaddr, params.len); + mmap_write_unlock(kvm->mm); + if (ret) + return -EFAULT; + /* * The userspace memory is already locked so technically we don't * need to lock it again. Later part of the function needs to know
When SEV-SNP is enabled, the guest private pages are added in the RMP table; while adding the pages, the rmp_make_private() unmaps the pages from the direct map. If KSM attempts to access those unmapped pages then it will trigger #PF (page-not-present). Encrypted guest pages cannot be shared between the process, so an userspace should not mark the region mergeable but to be safe, mark the process vma unmerable before adding the pages in the RMP table. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- arch/x86/kvm/svm/sev.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+)