Re: [PATCH RFC v7 10/64] KVM: SEV: Populate private memory fd during LAUNCH_UPDATE_DATA

[Michael Roth]

On Wed, Jan 18, 2023 at 01:42:45AM +0200, Jarkko Sakkinen wrote:
> On Wed, Dec 14, 2022 at 01:40:02PM -0600, Michael Roth wrote:
> > From: Vishal Annapurve <vannapurve@xxxxxxxxxx>
> > 
> > This change adds handling of HVA ranges to copy contents
> > to private memory while doing sev launch update data.
> > 
> > mem_attr array is updated during LAUNCH_UPDATE_DATA to ensure
> > that encrypted memory is marked as private.
> > 
> > Signed-off-by: Vishal Annapurve <vannapurve@xxxxxxxxxx>
> > [mdr: use gfn_to_hva_memslot_prot() for shared GFN handler to deal with
> >       read-only slots for ROMs]
> > Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> > ---
> >  arch/x86/kvm/svm/sev.c   | 99 ++++++++++++++++++++++++++++++++++++----
> >  include/linux/kvm_host.h |  1 +
> >  virt/kvm/kvm_main.c      | 27 ++++++++---
> >  3 files changed, 111 insertions(+), 16 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 69dbf17f0d6a..a7e4e3005786 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -493,23 +493,26 @@ static unsigned long get_num_contig_pages(unsigned long idx,
> >  	return pages;
> >  }
> >  
> > -static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
> > +static int sev_launch_update_shared_gfn_handler(struct kvm *kvm,
> > +						struct kvm_gfn_range *range,
> > +						struct kvm_sev_cmd *argp)
> >  {
> >  	unsigned long vaddr, vaddr_end, next_vaddr, npages, pages, size, i;
> >  	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> > -	struct kvm_sev_launch_update_data params;
> >  	struct sev_data_launch_update_data data;
> >  	struct page **inpages;
> >  	int ret;
> >  
> > -	if (!sev_guest(kvm))
> > -		return -ENOTTY;
> > -
> > -	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
> > -		return -EFAULT;
> > +	vaddr = gfn_to_hva_memslot_prot(range->slot, range->start, NULL);
> > +	pr_debug("%s: shared GFN: %llx, slot.id: %d, slot.base_gfn: %llx, slot.userspace_addr: %lx, slot.flags: %x, vaddr: %lx\n",
> > +		 __func__, range->start, range->slot->id, range->slot->base_gfn,
> > +		 range->slot->userspace_addr, range->slot->flags, vaddr);
> > +	if (kvm_is_error_hva(vaddr)) {
> > +		pr_err("vaddr is erroneous 0x%lx\n", vaddr);
> > +		return -EINVAL;
> > +	}
> >  
> > -	vaddr = params.uaddr;
> > -	size = params.len;
> > +	size = (range->end - range->start) << PAGE_SHIFT;
> >  	vaddr_end = vaddr + size;
> >  
> >  	/* Lock the user memory. */
> > @@ -561,6 +564,84 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
> >  	return ret;
> >  }
> >  
> > +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);
> > +			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))
> > +			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 */);
> > +
> > +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;
> > +
> > +	return kvm_vm_do_hva_range_op(kvm, params.uaddr, params.uaddr + params.len,
> > +		sev_launch_update_gfn_handler, argp);
> > +}
> > +
> >  static int sev_es_sync_vmsa(struct vcpu_svm *svm)
> >  {
> >  	struct sev_es_save_area *save = svm->sev_es.vmsa;
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index 21a539ab17f6..33fa0b1435d3 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -973,6 +973,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> >  void kvm_exit(void);
> >  
> >  void kvm_get_kvm(struct kvm *kvm);
> > +int kvm_vm_set_region_attr(struct kvm *kvm, gfn_t start, gfn_t end, u64 attributes);
> >  bool kvm_get_kvm_safe(struct kvm *kvm);
> >  void kvm_put_kvm(struct kvm *kvm);
> >  bool file_is_kvm(struct file *file);
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 4ff7adaf6c56..1343070657d1 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -747,6 +747,7 @@ int kvm_vm_do_hva_range_op(struct kvm *kvm, unsigned long hva_start,
> >  
> >  	return ret;
> >  }
> > +EXPORT_SYMBOL_GPL(kvm_vm_do_hva_range_op);
> >  
> >  static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
> >  						unsigned long start,
> > @@ -2595,12 +2596,28 @@ static void kvm_unmap_mem_range(struct kvm *kvm, gfn_t start, gfn_t end,
> >  		kvm_flush_remote_tlbs(kvm);
> >  }
> >  
> > +int kvm_vm_set_region_attr(struct kvm *kvm, gfn_t start, gfn_t end,
> > +			   u64 attributes)
> > +{
> > +	gfn_t index;
> > +	void *entry;
> > +
> > +	entry = attributes ? xa_mk_value(attributes) : NULL;
> > +
> > +	for (index = start; index < end; index++)
> > +		if (xa_err(xa_store(&kvm->mem_attr_array, index, entry,
> > +				    GFP_KERNEL_ACCOUNT)))
> > +			break;
> > +
> > +	return index;
> > +}
> > +EXPORT_SYMBOL_GPL(kvm_vm_set_region_attr);
> > +
> >  static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> >  					   struct kvm_memory_attributes *attrs)
> >  {
> >  	gfn_t start, end;
> >  	unsigned long i;
> > -	void *entry;
> >  	int idx;
> >  	u64 supported_attrs = kvm_supported_mem_attributes(kvm);
> >  
> > @@ -2617,8 +2634,6 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> >  	start = attrs->address >> PAGE_SHIFT;
> >  	end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT;
> >  
> > -	entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL;
> > -
> >  	if (kvm_arch_has_private_mem(kvm)) {
> >  		KVM_MMU_LOCK(kvm);
> >  		kvm_mmu_invalidate_begin(kvm);
> > @@ -2627,10 +2642,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> >  	}
> >  
> >  	mutex_lock(&kvm->lock);
> > -	for (i = start; i < end; i++)
> > -		if (xa_err(xa_store(&kvm->mem_attr_array, i, entry,
> > -				    GFP_KERNEL_ACCOUNT)))
> > -			break;
> > +	i = kvm_vm_set_region_attr(kvm, start, end, attrs->attributes);
> >  	mutex_unlock(&kvm->lock);
> >  
> >  	if (kvm_arch_has_private_mem(kvm)) {
> > @@ -2793,6 +2805,7 @@ unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot,
> >  
> >  	return hva;
> >  }
> > +EXPORT_SYMBOL_GPL(gfn_to_hva_memslot_prot);
> >  
> >  unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable)
> >  {
> > -- 
> > 2.25.1
> > 
> 
> Hmm.. but user space is still allowed to call KVM_SET_MEMORY_ATTRIBUTES
> with KVM_MEMORY_ATTRIBUTE_PRIVATE set? How do these behaviours complement
> each other?

In the current series it's allowed. It reduces some headaches since an
SNP guest can issue duplicate page-state changes without violating the
spec, and it would complicate things further if kernel/userspace
attempted to enforce something stricter.

> 
> SEV specific changes and kvm_vm_set_region_attr() definition should really
> be separate patches.

Done.

-Mike

> 
> BR, Jarkko