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SubjectRe: [RFC Part2 PATCH v3 21/26] KVM: SVM: Add support for SEV DEBUG_ENCRYPT command
On Mon, Jul 24, 2017 at 03:02:58PM -0500, Brijesh Singh wrote:
> The command copies a plain text into guest memory and encrypts it using
> the VM encryption key. The command will be used for debug purposes
> (e.g setting breakpoint through gdbserver)

"setting a breakpoint" or "setting breakpoints"

>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> arch/x86/kvm/svm.c | 174 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 174 insertions(+)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 933384a..75dcaa9 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6214,6 +6214,176 @@ static int sev_dbg_decrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
> return ret;
> }
>
> +static int __sev_dbg_enc(struct kvm *kvm, unsigned long __user vaddr,

__sev_dbg_encrypt

> + unsigned long paddr, unsigned long __user dst_vaddr,
> + unsigned long dst_paddr, int size, int *error)
> +{
> + struct page *src_tpage = NULL;
> + struct page *dst_tpage = NULL;
> + int ret, len = size;
> +
> + /*
> + * Debug encrypt command works with 16-byte aligned inputs. Function
> + * handles the alingment issue as below:
> + *
> + * case 1
> + * If source buffer is not 16-byte aligned then we copy the data from
> + * source buffer into a PAGE aligned intermediate (src_tpage) buffer

"page-aligned"

> + * and use this intermediate buffer as source buffer
> + *
> + * case 2
> + * If destination buffer or length is not 16-byte aligned then:
> + * - decrypt portion of destination buffer into intermediate buffer
> + * (dst_tpage)
> + * - copy the source data into intermediate buffer
> + * - use the intermediate buffer as source buffer
> + */
> +
> + /* If source is not aligned (case 1) */

So put the whole case 1 comment here directly - no need to reference it
again. Ditto for case 2 below.

> + if (!IS_ALIGNED(vaddr, 16)) {
> + src_tpage = alloc_page(GFP_KERNEL);
> + if (!src_tpage)
> + return -ENOMEM;
> +
> + if (copy_from_user(page_address(src_tpage),
> + (uint8_t *)vaddr, size)) {

Let it stick out.

> + __free_page(src_tpage);
> + return -EFAULT;
> + }
> + paddr = __sme_page_pa(src_tpage);
> +
> + /* flush the caches to ensure that DRAM has recent contents */

That comment needs improving.

> + clflush_cache_range(page_address(src_tpage), PAGE_SIZE);
> + }
> +
> + /* If destination buffer or length is not aligned (case 2) */
> + if (!IS_ALIGNED(dst_vaddr, 16) || !IS_ALIGNED(size, 16)) {
> + int dst_offset;
> +
> + dst_tpage = alloc_page(GFP_KERNEL);
> + if (!dst_tpage) {
> + ret = -ENOMEM;
> + goto e_free;
> + }
> +
> + /* decrypt destination buffer into intermediate buffer */
> + ret = __sev_dbg_dec(kvm,
> + round_down(dst_paddr, 16),
> + 0,
> + (unsigned long)page_address(dst_tpage),
> + __sme_page_pa(dst_tpage),
> + round_up(size, 16),
> + error);
> + if (ret)
> + goto e_free;
> +
> + dst_offset = dst_paddr & 15;
> +
> + /*
> + * modify the intermediate buffer with data from source
> + * buffer.
> + */
> + if (src_tpage)
> + memcpy(page_address(dst_tpage) + dst_offset,
> + page_address(src_tpage), size);
> + else {
> + if (copy_from_user(page_address(dst_tpage) + dst_offset,
> + (void *) vaddr, size)) {

Let it stick out.

> + ret = -EFAULT;
> + goto e_free;
> + }
> + }
> +
> +
> + /* use intermediate buffer as source */
> + paddr = __sme_page_pa(dst_tpage);
> +
> + /* flush the caches to ensure that DRAM gets recent updates */

Comment needs improvement.

> + clflush_cache_range(page_address(dst_tpage), PAGE_SIZE);
> +
> + /* now we have length and destination buffer aligned */
> + dst_paddr = round_down(dst_paddr, 16);
> + len = round_up(size, 16);
> + }
> +
> + ret = __sev_dbg_enc_dec(kvm, paddr, dst_paddr, len, error, true);

<---- newline here.

> +e_free:
> + if (src_tpage)
> + __free_page(src_tpage);
> + if (dst_tpage)
> + __free_page(dst_tpage);
> + return ret;
> +}
> +
> +static int sev_dbg_encrypt(struct kvm *kvm, struct kvm_sev_cmd *argp)
> +{

This function is almost an exact duplication of sev_dbg_decrypt(). Add
a __sev_dbg_crypt() workhorse function which does it all and has callers
sev_dbg_decrypt() and sev_dbg_encrypt().

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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