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    SubjectRe: [PATCH RFC v7 10/64] KVM: SEV: Populate private memory fd during LAUNCH_UPDATE_DATA
    On Fri, Jan 13, 2023 at 08:11:14PM +0100, Borislav Petkov wrote:
    > On Wed, Dec 14, 2022 at 01:40:02PM -0600, Michael Roth wrote:
    > > From: Vishal Annapurve <vannapurve@google.com>
    > >
    > > This change adds handling of HVA ranges to copy contents
    >
    > s/This change adds handling of/Handle/
    >
    > > +static int sev_launch_update_priv_gfn_handler(struct kvm *kvm,
    > > + struct kvm_gfn_range *range,
    > > + struct kvm_sev_cmd *argp)
    > > +{
    > > + struct sev_data_launch_update_data data;
    > > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
    > > + gfn_t gfn;
    > > + kvm_pfn_t pfn;
    > > + struct kvm_memory_slot *memslot = range->slot;
    > > + int ret = 0;
    > > +
    > > + data.reserved = 0;
    > > + data.handle = sev->handle;
    > > +
    > > + for (gfn = range->start; gfn < range->end; gfn++) {
    > > + int order;
    > > + void *kvaddr;
    > > +
    > > + ret = kvm_restricted_mem_get_pfn(memslot, gfn, &pfn, &order);
    > > + if (ret)
    > > + return ret;
    > > +
    > > + kvaddr = pfn_to_kaddr(pfn);
    > > + if (!virt_addr_valid(kvaddr)) {
    > > + pr_err("Invalid kvaddr 0x%llx\n", (uint64_t)kvaddr);
    >
    > Is that some debugging help leftover or what is that printk issued for?

    A mix of error-reporting and debugging I think. I think the error message
    isn't needed since the error value will get plumbed straight to
    userspace and anything beyond that is kernel debugging, so I added some
    context and switched this to pr_debug().

    > > + ret = -EINVAL;
    > > + goto e_ret;
    > > + }
    > > +
    > > + ret = kvm_read_guest_page(kvm, gfn, kvaddr, 0, PAGE_SIZE);
    > > + if (ret) {
    > > + pr_err("guest read failed 0x%x\n", ret);
    > > + goto e_ret;
    > > + }
    > > +
    > > + if (!this_cpu_has(X86_FEATURE_SME_COHERENT))
    >
    > check_for_deprecated_apis: WARNING: arch/x86/kvm/svm/sev.c:602: Do not use this_cpu_has() - use cpu_feature_enabled() instead.
    >
    > > + clflush_cache_range(kvaddr, PAGE_SIZE);
    > > +
    > > + data.len = PAGE_SIZE;
    > > + data.address = __sme_set(pfn << PAGE_SHIFT);
    > > + ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_DATA, &data, &argp->error);
    > > + if (ret)
    > > + goto e_ret;
    > > + kvm_release_pfn_clean(pfn);
    > > + }
    > > + kvm_vm_set_region_attr(kvm, range->start, range->end,
    > > + true /* priv_attr */);
    >
    > No need to break that line.
    >
    > > +
    > > +e_ret:
    > > + return ret;
    > > +}
    > > +
    > > +static int sev_launch_update_gfn_handler(struct kvm *kvm, struct kvm_gfn_range *range,
    > > + void *data)
    > > +{
    > > + struct kvm_sev_cmd *argp = (struct kvm_sev_cmd *)data;
    > > +
    > > + if (kvm_slot_can_be_private(range->slot))
    > > + return sev_launch_update_priv_gfn_handler(kvm, range, argp);
    > > +
    > > + return sev_launch_update_shared_gfn_handler(kvm, range, argp);
    > > +}
    > > +
    > > +static int sev_launch_update_data(struct kvm *kvm,
    > > + struct kvm_sev_cmd *argp)
    > > +{
    > > + struct kvm_sev_launch_update_data params;
    > > +
    > > + if (!sev_guest(kvm))
    > > + return -ENOTTY;
    > > +
    > > + if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
    > > + return -EFAULT;
    >
    > Not gonna check those user-supplied values for sanity?
    >
    > Or is this check
    >
    > if (WARN_ON_ONCE(hva_end <= hva_start))
    > return -EINVAL;
    >
    > in kvm_vm_do_hva_range_op() enough?

    Only partially, but kvm_vm_do_hva_range_op() should sanitize the address
    range and only call sev_launch_update_gfn_handler() on valid GFNs within
    the range, so if userspace provides a bogus HVA range that doesn't
    actually correspond to a valid memslot it'll simply be treated as a
    no-op.

    -Mike

    >
    > Thx.
    >
    > --
    > Regards/Gruss,
    > Boris.
    >
    > https://people.kernel.org/tglx/notes-about-netiquette

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