[librm] Add support for installing a startup IPI handler

Application processors are started via INIT and SIPI interprocessor
interrupts: the INIT places the processor into a "wait for SIPI"
state, and the SIPI then starts the processor in real mode at a
page-aligned address derived from the SIPI vector number.

Add support for installing a real-mode SIPI handler that will switch
the CPU into protected mode with flat physical addressing, load
initial register contents, and then jump to the address of a
protected-mode SIPI handler.  No stack pointer is set up, to avoid the
need to allocate stack space for each available processor.

We use 32-bit physical addressing in order to minimise the changes
required for a 64-bit build.  The existing long mode transition code
relies on the existence of the stack, so we cannot easily switch the
application processor into long mode.  We could use 32-bit virtual
addressing, but this runtime environment does not currently exist
outside of librm.S itself in a 64-bit build, and using it would
complicate the implementation of the protected-mode SIPI handler.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/src/arch/x86/include/librm.h b/src/arch/x86/include/librm.h
index 40f075439..84b345d3a 100644
--- a/src/arch/x86/include/librm.h
+++ b/src/arch/x86/include/librm.h
@@ -474,6 +474,26 @@ extern struct page_table io_pages;
  */
 #define IO_BASE ( ( void * ) 0x100000000ULL )
 
+/** Startup IPI real-mode handler */
+extern char __text16_array ( sipi, [] );
+#define sipi __use_text16 ( sipi )
+
+/** Length of startup IPI real-mode handler */
+extern char sipi_len[];
+
+/** Startup IPI real-mode handler copy of real-mode data segment */
+extern uint16_t __text16 ( sipi_ds );
+#define sipi_ds __use_text16 ( sipi_ds )
+
+/** Startup IPI protected-mode handler (physical address) */
+extern uint32_t sipi_handler;
+
+/** Startup IPI register state */
+extern struct i386_regs sipi_regs;
+
+extern void setup_sipi ( unsigned int vector, uint32_t handler,
+			 struct i386_regs *regs );
+
 #endif /* ASSEMBLY */
 
 #endif /* LIBRM_H */