Re: [PATCH v10 2/2] x86/tdx: Support vmalloc() for tdx_enc_status_changed()

[Edgecombe, Rick P]

On Fri, 2023-08-11 at 14:48 -0700, Dexuan Cui wrote:
> When a TDX guest runs on Hyper-V, the hv_netvsc driver's
> netvsc_init_buf()
> allocates buffers using vzalloc(), and needs to share the buffers
> with the
> host OS by calling set_memory_decrypted(), which is not working for
> vmalloc() yet. Add the support by handling the pages one by one.
> 
> Co-developed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> Reviewed-by: Kuppuswamy Sathyanarayanan
> <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> ---
>  arch/x86/coco/tdx/tdx.c | 36 ++++++++++++++++++++++++++++++------
>  1 file changed, 30 insertions(+), 6 deletions(-)

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

Only small comment, it is possible to have huge vmalloc's now, which
would mean this would do 512 TDVMCALL_MAP_GPA calls instead of 1 when
encountering a huge vmalloc mapping. If this used lookup_address()
directly instead of slow_virt_to_phys(), it could catch this case. I
don't think there are any cases of huge vmallocs today that would get
passed into set_memory_en/decrypted(), so would only be future
proofing.