On Monday 23 October 2006 22:37, Avi Kivity wrote:
> Arnd Bergmann wrote:
> > On Monday 23 October 2006 22:16, Avi Kivity wrote:
> >>> This looks like you should simply put it into a .S file.
> >>
> >> Then I lose all the offsetof constants down the line. Sure, I could do
> >> the asm-offsets dance but it seems to me like needless obfuscation.
> >
> > Ok, I see.
> >
> > How if you pass &vcpu->regs and &vcpu->cr2 to the functions instead of
> > kvm_vcpu?
>
> I could do that, but I feel that's more brittle. I might need more (or
> other) fields later on. It will also cost me more pushes on the stack
> (no real performance or space impact, just C64-era frugality).
Maybe you could save some more stack usage by doing something like this:
static inline void vmlaunch(struct kvm_vcpu *vcpu)
{
register unsigned long rax asm("rax");
register unsigned long rbx asm("rbx");
register unsigned long rcx asm("rcx");
register unsigned long rdx asm("rdx");
register unsigned long rsi asm("rsi");
register unsigned long rdi asm("rdi");
register unsigned long rbp asm("rbp");
register unsigned long r8 asm("r8");
register unsigned long r9 asm("r9");
register unsigned long r10 asm("r10");
register unsigned long r11 asm("r11");
register unsigned long r12 asm("r12");
register unsigned long r13 asm("r13");
register unsigned long r14 asm("r14");
register unsigned long r15 asm("r15");
asm ("mov %%cr2, %0" : : "r" (vcpu->cr2));
rax = vcpu->regs[VCPU_REGS_RAX];
rbx = vcpu->regs[VCPU_REGS_RBX];
rcx = vcpu->regs[VCPU_REGS_RCX];
rdx = vcpu->regs[VCPU_REGS_RDX];
rsi = vcpu->regs[VCPU_REGS_RSI];
rdi = vcpu->regs[VCPU_REGS_RDI];
rbp = vcpu->regs[VCPU_REGS_RBP];
r8 = vcpu->regs[VCPU_REGS_R8 ];
r9 = vcpu->regs[VCPU_REGS_R9 ];
r10 = vcpu->regs[VCPU_REGS_R10];
r11 = vcpu->regs[VCPU_REGS_R11];
r12 = vcpu->regs[VCPU_REGS_R12];
r13 = vcpu->regs[VCPU_REGS_R13];
r14 = vcpu->regs[VCPU_REGS_R14];
r15 = vcpu->regs[VCPU_REGS_R15];
asm ("vmlaunch\n\t" :
"+r" (rax),
"+r" (rbx),
"+r" (rcx),
"+r" (rdx),
"+r" (rsi),
"+r" (rdi),
"+r" (rbp),
"+r" (r8),
"+r" (r9),
"+r" (r10),
"+r" (r11),
"+r" (r12),
"+r" (r13),
"+r" (r14),
"+r" (r15)
);
vcpu->regs[VCPU_REGS_RAX] = rax;
vcpu->regs[VCPU_REGS_RBX] = rbx;
vcpu->regs[VCPU_REGS_RCX] = rcx;
vcpu->regs[VCPU_REGS_RDX] = rdx;
vcpu->regs[VCPU_REGS_RSI] = rsi;
vcpu->regs[VCPU_REGS_RDI] = rdi;
vcpu->regs[VCPU_REGS_RBP] = rbp;
vcpu->regs[VCPU_REGS_R8 ] = r8 ;
vcpu->regs[VCPU_REGS_R9 ] = r9 ;
vcpu->regs[VCPU_REGS_R10] = r10;
vcpu->regs[VCPU_REGS_R11] = r11;
vcpu->regs[VCPU_REGS_R12] = r12;
vcpu->regs[VCPU_REGS_R13] = r13;
vcpu->regs[VCPU_REGS_R14] = r14;
vcpu->regs[VCPU_REGS_R15] = r15;
asm ("mov %0, %%cr2" : "=r" (vcpu->cr2));
}
Unfortunately, I couldn't get this to do the right thing with the output
flags. Unless I missed something, your solution is really the best one you
can express in gcc.
Arnd <><
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