crypto: ccp: Play nice with vmalloc'd memory for SEV command structs

Copy the incoming @data comman to an internal buffer so that callers can
put SEV command buffers on the stack without running afoul of
CONFIG_VMAP_STACK=y, i.e. without bombing on vmalloc'd pointers.  As of
today, the largest supported command takes a 68 byte buffer, i.e. pretty
much every command can be put on the stack.  Because sev_cmd_mutex is
held for the entirety of a transaction, only a single bounce buffer is
required.

Use the internal buffer unconditionally, as the majority of in-kernel
users will soon switch to using the stack.  At that point, checking
virt_addr_valid() becomes (negligible) overhead in most cases, and
supporting both paths slightly increases complexity.  Since the commands
are all quite small, the cost of the copies is insignificant compared to
the latency of communicating with the PSP.

Allocate a full page for the buffer as opportunistic preparation for
SEV-SNP, which requires the command buffer to be in firmware state for
commands that trigger memory writes from the PSP firmware.  Using a full
page now will allow SEV-SNP support to simply transition the page as
needed.

Cc: Brijesh Singh <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Christophe Leroy <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Brijesh Singh <[email protected]>
Acked-by: Tom Lendacky <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

0 files changed, 0 insertions, 0 deletions