Re: [PATCH kernel 5/9] x86/mm: Stop forcing decrypted page state for TDISP devices

[dan.j.williams]

Alexey Kardashevskiy wrote:
> The DMA subsystem does is forcing private-to-shared
> page conversion in force_dma_unencrypted().
> 
> Return false from force_dma_unencrypted() for TDISP devices.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxx>
> ---
>  arch/x86/mm/mem_encrypt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 95bae74fdab2..8daa6482b080 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -20,10 +20,11 @@
>  bool force_dma_unencrypted(struct device *dev)
>  {
>  	/*
> -	 * For SEV, all DMA must be to unencrypted addresses.
> +	 * dma_direct_alloc() forces page state change if private memory is
> +	 * allocated for DMA. Skip conversion if the TDISP device is accepted.

Looks ok, but I would not reference "TDISP" here. TDISP is the PCI
"accept" protocol. Other buses might accept devices via other
bus-specific protocols.