Re: [RFC Part2 PATCH v3 16/26] KVM: SVM: Add support for SEV LAUNCH_UPDATE_DATA command

[Borislav Petkov]

On Mon, Jul 24, 2017 at 03:02:53PM -0500, Brijesh Singh wrote:
> The command is used for encrypting the guest memory region using the VM
> encryption key (VEK) created during LAUNCH_START.

Yap, this is one good commit message!

:-)

> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> ---
>  arch/x86/kvm/svm.c | 165 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 165 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 3e325578..91b070f 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -39,6 +39,8 @@
>  #include <linux/frame.h>
>  #include <linux/psp-sev.h>
>  #include <linux/file.h>
> +#include <linux/pagemap.h>
> +#include <linux/swap.h>
>  
>  #include <asm/apic.h>
>  #include <asm/perf_event.h>
> @@ -331,6 +333,7 @@ static int sev_asid_new(void);
>  static void sev_asid_free(int asid);
>  static void sev_deactivate_handle(struct kvm *kvm, int *error);
>  static void sev_decommission_handle(struct kvm *kvm, int *error);
> +#define __sme_page_pa(x) __sme_set(page_to_pfn(x) << PAGE_SHIFT)
>  
>  static bool svm_sev_enabled(void)
>  {
> @@ -5796,6 +5799,164 @@ static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  	return ret;
>  }
>  
> +static struct page **sev_pin_memory(unsigned long uaddr, unsigned long ulen,
> +				    unsigned long *n, int write)
> +{
> +	unsigned long npages, pinned, size;
> +	struct page **pages;
> +	int first, last;
> +
> +	/* Get number of pages */
> +	first = (uaddr & PAGE_MASK) >> PAGE_SHIFT;
> +	last = ((uaddr + ulen - 1) & PAGE_MASK) >> PAGE_SHIFT;
> +	npages = (last - first + 1);
> +
> +	/* Avoid using vmalloc for smaller buffer */
> +	size = npages * sizeof(struct page *);
> +	if (size > PAGE_SIZE)
> +		pages = vmalloc(size);
> +	else
> +		pages = kmalloc(size, GFP_KERNEL);
> +
> +	if (!pages)
> +		return NULL;
> +
> +	/* pin the user virtual address */
> +	pinned = get_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0,
> +					pages);

Let it stick out.

> +	if (pinned != npages) {
> +		pr_err("failed to pin %ld pages (got %ld)\n", npages, pinned);
> +		goto err;
> +	}
> +
> +	*n = npages;
> +	return pages;
> +err:
> +	if (pinned > 0)
> +		release_pages(pages, pinned, 0);

<---- newline here.

> +	kvfree(pages);
> +
> +	return NULL;
> +}
> +
> +static void sev_unpin_memory(struct page **pages, unsigned long npages)
> +{
> +	release_pages(pages, npages, 0);
> +	kvfree(pages);
> +}
> +
> +static void sev_clflush_pages(struct page *pages[], unsigned long npages)
> +{
> +	uint8_t *page_virtual;
> +	unsigned long i;
> +
> +	if (npages == 0 || pages == NULL)
> +		return;
> +
> +	for (i = 0; i < npages; i++) {
> +		page_virtual = kmap_atomic(pages[i]);
> +		clflush_cache_range(page_virtual, PAGE_SIZE);
> +		kunmap_atomic(page_virtual);
> +	}
> +}
> +
> +static int get_num_contig_pages(int idx, struct page **inpages,
> +				unsigned long npages)
> +{
> +	int i = idx + 1, pages = 1;
> +	unsigned long paddr, next_paddr;
> +
> +	/* find the number of contiguous pages starting from idx */
> +	paddr = __sme_page_pa(inpages[idx]);
> +	while (i < npages) {
> +		next_paddr = __sme_page_pa(inpages[i++]);
> +		if ((paddr + PAGE_SIZE) == next_paddr) {
> +			pages++;
> +			paddr = next_paddr;
> +			continue;
> +		}
> +		break;
> +	}
> +
> +	return pages;
> +}
> +
> +static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{
> +	unsigned long vaddr, vaddr_end, next_vaddr, npages, size;
> +	struct kvm_sev_launch_update_data params;
> +	struct sev_data_launch_update_data *data;
> +	struct page **inpages;
> +	int i, ret, pages;
> +
> +	if (!sev_guest(kvm))
> +		return -ENOTTY;
> +
> +	if (copy_from_user(&params, (void *)argp->data,
> +			sizeof(struct kvm_sev_launch_update_data)))
> +		return -EFAULT;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;

Same issues as before.

> +
> +	vaddr = params.address;
> +	size = params.length;
> +	vaddr_end = vaddr + size;
> +
> +	/* lock the user memory */
> +	inpages = sev_pin_memory(vaddr, size, &npages, 1);

This way user basically controls how many pages to pin and you need to
limit that on the upper end.

> +	if (!inpages) {
> +		ret = -ENOMEM;
> +		goto e_free;
> +	}
> +
> +	/*
> +	 * invalidate the cache to ensure that DRAM has recent content before

recent content?

> +	 * calling the SEV commands.
> +	 */
> +	sev_clflush_pages(inpages, npages);
> +
> +	for (i = 0; vaddr < vaddr_end; vaddr = next_vaddr, i += pages) {
> +		int offset, len;
> +
> +		/*
> +		 * since user buffer may not be page aligned, calculate the
> +		 * offset within the page.
> +		 */
> +		offset = vaddr & (PAGE_SIZE - 1);
> +
> +		/*
> +		 * calculate the number of pages that can be encrypted in one go
> +		 */
> +		pages = get_num_contig_pages(i, inpages, npages);
> +
> +		len = min_t(size_t, ((pages * PAGE_SIZE) - offset), size);
> +
> +		data->handle = sev_get_handle(kvm);
> +		data->length = len;
> +		data->address = __sme_page_pa(inpages[i]) + offset;
> +		ret = sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE_DATA, data,
> +				&argp->error);

Yah, let it stick out.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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