[PATCH 0/2] KVM: riscv: Unify and optimize FP register loops

[Paul White <paul.white.kernel@gmail.com>]

The change to both patches in this series is a 
structural/architectural one. Both functions set_reg and get_reg use 
identical code to locate the register the application specified in the 
token even though they do different things with that location 
information: the set_reg function adds data the application requested 
to send to that identified location  (in the copy_from_user function) 
while the get_reg function retrieves what data is at that identified 
location and sends it to the application (using the copy_to_user 
function). Everything else is the same. That is the only difference 
between the code. 

Therefore I was able to apply the same solution to both of the 
function's finding-the-requested-register parts (which is everything 
up until the final if statement) which were filled with redundancy. 
The solution I came up with is to create local variables for the 
entire function for all the variables of the original code that would 
be different, depending on the floating point type. Then once I ask 
whether it is a double floating point or single floating point mode, I 
assign the aforementioned variables to the values they should have for 
that mode so that when I go through the if statements that ask whether 
the requested register number is a status control register or data 
register, I only have to go through it once because the respective 
floating point values/addresses would have been assigned to the 
aforementioned local variables, so the whole code kind of changes or 
is tailored to the floating point type. 

This architectural change/solution will make the cpu execute the code 
faster (as the cpu will have less decisions to make and the bare-metal 
math used to figure out the address of the register is executed faster 
by the cpu than looking up object properties and array indexes), is 
more maintainable, and is more readable.

Paul White (2):
  KVM: riscv: Eliminate redundancy in get_reg function via pointers
  KVM: riscv: Eliminate redundancy in set_reg function via pointers

 arch/riscv/kvm/vcpu_fp.c | 128 +++++++++++++++++++++++----------------
 1 file changed, 76 insertions(+), 52 deletions(-)

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2.53.0