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Differential D53804 Diff 166678 sys/riscv/riscv/vm_machdep.c

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sys/riscv/riscv/vm_machdep.c

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#include <vm/vm.h> #include <vm/vm.h>
#include <vm/vm_page.h> #include <vm/vm_page.h>
#include <vm/vm_map.h> #include <vm/vm_map.h>
#include <vm/uma.h> #include <vm/uma.h>
#include <vm/uma_int.h> #include <vm/uma_int.h>
#include <machine/riscvreg.h> #include <machine/riscvreg.h>
#include <machine/cpu.h> #include <machine/cpu.h>
#include <machine/fpe.h>
#include <machine/cpufunc.h> #include <machine/cpufunc.h>
#include <machine/pcb.h> #include <machine/pcb.h>
#include <machine/frame.h> #include <machine/frame.h>
#include <machine/sbi.h> #include <machine/sbi.h>
#if __riscv_xlen == 64 #if __riscv_xlen == 64
#define TP_OFFSET 16 /* sizeof(struct tcb) */ #define TP_OFFSET 16 /* sizeof(struct tcb) */
#endif #endif
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cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags) cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
{ {
struct pcb *pcb2; struct pcb *pcb2;
struct trapframe *tf; struct trapframe *tf;
if ((flags & RFPROC) == 0) if ((flags & RFPROC) == 0)
return; return;
/* RISCVTODO: save the FPU state here */ /* Ensure the floating-point state is saved before copying the pcb. */
if ((td1->td_pcb->pcb_fpflags & PCB_FP_STARTED) != 0) {
critical_enter();
fpe_state_save(td1);
critical_exit();
}
cpu_set_pcb_frame(td2); cpu_set_pcb_frame(td2);
pcb2 = td2->td_pcb; pcb2 = td2->td_pcb;
bcopy(td1->td_pcb, pcb2, sizeof(*pcb2)); bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
tf = td2->td_frame; tf = td2->td_frame;
bcopy(td1->td_frame, tf, sizeof(*tf)); bcopy(td1->td_frame, tf, sizeof(*tf));
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* thread, about to return to userspace. Put enough state in the new * thread, about to return to userspace. Put enough state in the new
* thread's PCB to get it to go back to the fork_return(), which * thread's PCB to get it to go back to the fork_return(), which
* finalizes the thread state and handles peculiarities of the first * finalizes the thread state and handles peculiarities of the first
* return to userspace for the new thread. * return to userspace for the new thread.
*/ */
void void
cpu_copy_thread(struct thread *td, struct thread *td0) cpu_copy_thread(struct thread *td, struct thread *td0)
{ {
mhorneUnsubmitted
Not Done
Inline Actions

Looking at other implementations, we need to save the FPE context here as well.

This one is invoked when creating a new thread in the same process, while above is invoked when forking/creating a new process.

mhorne: Looking at other implementations, we need to save the FPE context here as well. This one is…
jsihv_gmx.comAuthorUnsubmitted
Done
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AMD64 & PowerPC seem to be like what you say but it looks like ARM64 does not save FP registers in cpu_copy_thread()

ARM64 calls vfp_new_thread() in both functions but this function just makes some modifications to a new thread _after_ it has been copied. In the case of AMD64 these both functions cpu_copy_thread() and cpu_fork() share a lot of common code in copy_thread() which calls fpuexit() which saves (after some further calls) fp-registers and thus corresponds the new code in this patch. PowerPC seems to be similar to AMD64. Both functions call cpu_update_pcb() which saves fp-registers to pcb.

So a question can be asked, do AMD64 and PowerPC do this just because their functions share a common function call together or do these differences (AMD64 & PowerPC vs. ARM64) reflect more genuine differences between these archs.

jsihv_gmx.com: AMD64 & PowerPC seem to be like what you say but it looks like ARM64 does not save FP registers…
bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe)); bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe));
bcopy(td0->td_pcb, td->td_pcb, sizeof(struct pcb)); bcopy(td0->td_pcb, td->td_pcb, sizeof(struct pcb));
td->td_pcb->pcb_s[0] = (uintptr_t)fork_return; td->td_pcb->pcb_s[0] = (uintptr_t)fork_return;
td->td_pcb->pcb_s[1] = (uintptr_t)td; td->td_pcb->pcb_s[1] = (uintptr_t)td;
td->td_pcb->pcb_ra = (uintptr_t)fork_trampoline; td->td_pcb->pcb_ra = (uintptr_t)fork_trampoline;
td->td_pcb->pcb_sp = (uintptr_t)td->td_frame; td->td_pcb->pcb_sp = (uintptr_t)td->td_frame;
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