Fixes for secondary CPU start-up.
Changes to make secondary CPU start-up work on NetBSD, which depends
on some specific behavior in the architecture specification:
- Change the internal swppal() function to take the new VPTPTR and
Procedure Value as explicit arguments. Adapt do_start() to the
new the new swppal() signature.
- In do_start_wait(), extract the new VPTPTR and PV from the relevant
HWRPB fields, which will have been initialized by the OS, and pass
them to swppal().
- In the SWPPAL PAL call, get the value to stuff into PV (r27) from
a4 (r20), and add a comment describing why this implementation detail
is allowed by the architecture specification.
Signed-off-by: Jason Thorpe <thorpej@me.com>
Message-Id: <20210603035317.6814-9-thorpej@me.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/init.c b/init.c
index 1451785..6edfdf2 100644
--- a/init.c
+++ b/init.c
@@ -288,14 +288,16 @@
}
static void __attribute__((noreturn))
-swppal(void *entry, void *pcb)
+swppal(void *entry, void *pcb, unsigned long vptptr, unsigned long pv)
{
register int variant __asm__("$16") = 2; /* OSF/1 PALcode */
register void *pc __asm__("$17") = entry;
register unsigned long pa_pcb __asm__("$18") = PA(pcb);
- register unsigned long vptptr __asm__("$19") = VPTPTR;
+ register unsigned long newvptptr __asm__("$19") = vptptr;
+ register unsigned long newpv __asm__("$20") = pv;
- asm("call_pal 0x0a" : : "r"(variant), "r"(pc), "r"(pa_pcb), "r"(vptptr));
+ asm("call_pal 0x0a" : :
+ "r"(variant), "r"(pc), "r"(pa_pcb), "r"(newvptptr), "r"(newpv));
__builtin_unreachable ();
}
@@ -313,7 +315,9 @@
pci_setup();
vgahw_init();
- swppal(kernel_entry ? kernel_entry : do_console, &pcb);
+ void *new_pc = kernel_entry ? kernel_entry : do_console;
+
+ swppal(new_pc, &pcb, VPTPTR, (unsigned long)new_pc);
}
void
@@ -328,14 +332,16 @@
{
/* ??? The only message I know of is "START\r\n".
I can't be bothered to verify more than 4 characters. */
- /* ??? The Linux kernel fills in, but does not require,
- CPU_restart_data. It just sets that to the same address
- as CPU_restart itself. Our swppal *does* put the PC into
- $26 and $27, the latter of which the kernel does rely upon. */
+
+ /* Use use a private extension to SWPPAL to get the
+ CPU_restart_data into $27. Linux fills it in, but does
+ not require it. Other operating systems, however, do use
+ CPU_restart_data as part of secondary CPU start-up. */
unsigned int len = hwrpb.processor[cpuid].ipc_buffer[0];
unsigned int msg = hwrpb.processor[cpuid].ipc_buffer[1];
void *CPU_restart = hwrpb.hwrpb.CPU_restart;
+ unsigned long CPU_restart_data = hwrpb.hwrpb.CPU_restart_data;
__sync_synchronize();
hwrpb.hwrpb.rxrdy = 0;
@@ -343,7 +349,8 @@
{
/* Set bootstrap in progress */
hwrpb.processor[cpuid].flags |= 1;
- swppal(CPU_restart, hwrpb.processor[cpuid].hwpcb);
+ swppal(CPU_restart, hwrpb.processor[cpuid].hwpcb,
+ hwrpb.hwrpb.vptb, CPU_restart_data);
}
}
}
diff --git a/pal.S b/pal.S
index 015a829..8d55a0a 100644
--- a/pal.S
+++ b/pal.S
@@ -566,6 +566,8 @@
* r17 (a1) = New PC
* r18 (a2) = New PCB
* r19 (a3) = New VptPtr
+ * r20 (a4) = New Procedure Value (to place into $27)
+ * (Non-standard; See note below.)
*
* OUTPUT PARAMETERS:
*
@@ -574,11 +576,14 @@
* 1 - Unknown PALcode variant
* 2 - Known PALcode variant, but PALcode not loaded
*
- * r26 (ra) = r27 (pv) = New PC
+ * r26 (ra) = New PC
+ * r27 (pv) = From r20
* Note that this is non-architected, but is relied on by
* the usage of SwpPal within our own console code in order
- * to simplify its use within C code.
- *
+ * to simplify its use within C code. We can get away with
+ * the extra non-standard argument (in $20) because as
+ * architected, all registers except SP and R0 are
+ * UNPREDICTABLE; therefore private internal usage is fine.
*/
ORG_CALL_PAL_PRIV(0x0A)
CallPal_SwpPal:
@@ -624,7 +629,7 @@
mtpr $31, qemu_tbia // Flush TLB for new PTBR
mov a1, $26
- mov a1, $27
+ mov a4, $27
hw_ret (a1)
ENDFN CallPal_SwpPal_Cont
.previous
