RE: [RFC Part1 PATCH v3 13/17] x86/io: Unroll string I/O when SEV is active

David Laight
2017-07-25T09:51:13Z

From: Brijesh Singh
> Sent: 24 July 2017 20:08
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> Secure Encrypted Virtualization (SEV) does not support string I/O, so
> unroll the string I/O operation into a loop operating on one element at
> a time.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> arch/x86/include/asm/io.h | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index e080a39..2f3c002 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -327,14 +327,32 @@ static inline unsigned type in##bwl##_p(int port) \
> \
> static inline void outs##bwl(int port, const void *addr, unsigned long count) \
> {

Is it even worth leaving these as inline functions?
Given the speed of IO cycles it is unlikely that the cost of calling a real
function will be significant.
The code bloat reduction will be significant.

David