x86/sev: Make enc_dec_hypercall() accept a size instead of npages

x86/sev: Make enc_dec_hypercall() accept a size instead of npages

commit ac3f9c9f1b37edaa7d1a9b908bc79d843955a1a2 upstream.

enc_dec_hypercall() accepted a page count instead of a size, which
forced its callers to round up. As a result, non-page aligned
vaddrs caused pages to be spuriously marked as decrypted via the
encryption status hypercall, which in turn caused consistent
corruption of pages during live migration. Live migration requires
accurate encryption status information to avoid migrating pages
from the wrong perspective.

Fixes: 064ce6c550a0 ("mm: x86: Invoke hypercall when page encryption status is changed")
Signed-off-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Tested-by: Ben Hillier <bhillier@google.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230824223731.2055016-1-srutherford@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>