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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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