On 02/04/2010 05:55 PM, Alexander Graf wrote:
The one big thing about the Gekko is paired singles.
Paired singles are an extension to the instruction set, that adds 32 single
precision floating point registers (qprs), some SPRs to modify the behavior
of paired singled operations and instructions to deal with qprs to the
instruction set.
Unfortunately, it also changes semantics of existing operations that affect
single values in FPRs. In most cases they get mirrored to the coresponding
QPR.
Thanks to that we need to emulate all FPU operations and all the new paired
single operations too.
In order to achieve that, we take the guest's instruction, rip out the
parameters, put in our own and execute the very same instruction, but also
fix up the QPR values along the way.
That way we can execute paired single FPU operations without implementing a
soft fpu.
A little frightening. How many instructions are there? Maybe we can
just have an array of all of them followed by a return instruction, so
we don't jit code.
static void call_fpu_inst(u32 inst, u64 *out, u64 *in1, u64 *in2, u64 *in3,
+ u32 *cr, u32 *fpscr)
+{
+ u32 cr_val = 0;
+ u32 *call_stack;
+ u64 inout[5] = { 0, 0, 0, 0, 0 };
+
+ if (fpscr)
+ inout[0] = *fpscr;
+ if (in1)
+ inout[1] = *in1;
+ if (in2)
+ inout[2] = *in2;
+ if (in3)
+ inout[3] = *in3;
+ if (cr)
+ cr_val = *cr;
+
+ dprintk(KERN_INFO "FPU Emulator 0x%x ( 0x%llx, 0x%llx, 0x%llx )", inst,
+ inout[1], inout[2], inout[3]);
+
+ call_stack =&kvmppc_call_stack[(smp_processor_id() * 2)];
+ call_stack[0] = inst;
+ /* call_stack[1] is INS_BLR */
+
Would be easier on the cache to do this per-cpu?
--
error compiling committee.c: too many arguments to function
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