arch/riscv: Remove the current SBI implementation

This Supervisor Binary Interface, which is based on a page of code
that's provided to operating systems by the M-mode software, has been
superseded by a different (currently not really documented) SBI, which
is based on directly executing ECALLs instructions. Thus some of our
code becomes obsolete. Just rip it out until we implement the new SBI.

Change-Id: Iec9c20b750f39a2b8f1553e25865bbf150605a6d
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/22593
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 6 insertions, 29 deletions

diff --git a/src/arch/riscv/virtual_memory.c b/src/arch/riscv/virtual_memory.c
index 1fff1d170a..27b4b82fcc 100644
--- a/src/arch/riscv/virtual_memory.c
+++ b/src/arch/riscv/virtual_memory.c
@@ -16,7 +16,6 @@
 
 #include <arch/barrier.h>
 #include <arch/encoding.h>
-#include <arch/sbi.h>
 #include <atomic.h>
 #include <console/console.h>
 #include <stdint.h>
@@ -144,7 +143,6 @@ pte_t pte_create(uintptr_t ppn, int prot, int user)
 // The current RISCV *physical* address space is this:
 // * 0 - 2 GiB: miscellaneous IO devices
 // * 2 GiB - 4 GiB DRAM
-// * top 2048 bytes of memory: SBI (which we round out to a 4K page)
 // We have determined, also, that if code references a physical address
 // not backed by a device, we'll take a fault. In other words, we don't
 // need to finely map the memory-mapped devices as we would on an x86.
@@ -166,16 +164,11 @@ pte_t pte_create(uintptr_t ppn, int prot, int user)
 // I.e. we use 1 GiB PTEs for 4 GiB.
 // Linux/BSD uses this mapping just enough to replace it.
 //
-// The SBI page is the last page in the 64 bit address space.
-// map that using the middle_pts shown below.
+// Top 2G map: map the 2 Gib - 4 GiB of physical address space to
+// 0xffffffff_80000000. This will be needed until the GNU toolchain can compile
+// code to run at 0xffffffc000000000, i.e. the start of Sv39.
 //
-// Top 2G map, including SBI page: map the 2 Gib - 4 GiB of physical
-// address space to 0xffffffff_80000000. This will be needed until the
-// GNU toolchain can compile code to run at 0xffffffc000000000,
-// i.e. the start of Sv39.
-//
-// Only Harvey/Plan 9 uses this Mapping, and temporarily.  It can
-// never be full removed as we need the 4KiB mapping for the SBI page.
+// Only Harvey/Plan 9 uses this Mapping, and temporarily.
 //
 // standard RISCV map long term: Map IO space, and all of DRAM, to the *lowest*
 // possible negative address for this implementation,
@@ -187,15 +180,13 @@ pte_t pte_create(uintptr_t ppn, int prot, int user)
 // It is our intent on Harvey (and eventually Akaros) that we use
 // this map, once the toolchain can correctly support it.
 // We have tested this arrangement and it lets us boot harvey to user mode.
-void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, pte_t *sbi_pt)
+void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, pte_t *pt)
 {
-	memset(sbi_pt, 0, RISCV_PGSIZE);
-	// need to leave room for sbi page
 	// 0xFFF... - 0xFFFFFFFF81000000 - RISCV_PGSIZE
 	intptr_t memorySize = 0x7F000000;
 
 	// middle page table
-	pte_t* middle_pt = (void*)sbi_pt + RISCV_PGSIZE;
+	pte_t* middle_pt = (void*)pt;
 	size_t num_middle_pts = 2; // 3 level page table, 39 bit virtual address space for now
 
 	// root page table
@@ -215,20 +206,6 @@ void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, pte_t *sbi_pt)
 					       PTE_U|PTE_R|PTE_W|PTE_X, 0);
 	}
 
-	// map SBI at top of vaddr space
-	// only need to map a single page for sbi interface
-	uintptr_t num_sbi_pages = 1;
-	uintptr_t sbiStartAddress = (uintptr_t) &sbi_page;
-	uintptr_t sbiAddr = sbiStartAddress;
-	for (uintptr_t i = 0; i < num_sbi_pages; i++) {
-		uintptr_t idx = (1 << RISCV_PGLEVEL_BITS) - num_sbi_pages + i;
-		sbi_pt[idx] = pte_create(sbiAddr >> RISCV_PGSHIFT,
-					 PTE_R|PTE_X, 0);
-		sbiAddr += RISCV_PGSIZE;
-	}
-	pte_t* sbi_pte = middle_pt + ((num_middle_pts << RISCV_PGLEVEL_BITS)-1);
-	*sbi_pte = ptd_create((uintptr_t)sbi_pt >> RISCV_PGSHIFT);
-
 	// IO space. Identity mapped.
 	root_pt[0x000] = pte_create(0x00000000 >> RISCV_PGSHIFT,
 				PTE_R | PTE_W, 0);