On 06/26/2013 09:00:34 PM, Kevin Hao wrote:
diff --git a/arch/powerpc/include/asm/mmu-book3e.h
b/arch/powerpc/include/asm/mmu-book3e.h
index 936db36..bf422db 100644
--- a/arch/powerpc/include/asm/mmu-book3e.h
+++ b/arch/powerpc/include/asm/mmu-book3e.h
@@ -214,6 +214,11 @@
#define TLBILX_T_CLASS2 6
#define TLBILX_T_CLASS3 7
+#ifdef CONFIG_PPC32
+/* The max size that one tlb can map in a 32bit kernel. */
+#define PPC_PIN_SIZE (1 << 28) /* 256M */
+#endif
That comment is not true for all chips.
@@ -177,11 +178,34 @@ unsigned long map_mem_in_cams(unsigned long
ram, int max_cam_idx)
unsigned long virt = PAGE_OFFSET;
phys_addr_t phys = memstart_addr;
unsigned long amount_mapped = 0;
-
+ unsigned long cam_sz;
+
+#if defined(CONFIG_RELOCATABLE) && defined(CONFIG_PPC32)
+ /*
+ * For a relocatable kernel, we would not map from
memstart_addr.
+ * We first align to PPC_PIN_SIZE (256M), then map the
PAGE_OFFSET
+ * from there.
+ */
+ phys &= ~(PPC_PIN_SIZE - 1);
+ ram += memstart_addr & (PPC_PIN_SIZE - 1);
You should not map anything before memstart_addr. If memstart_addr
isn't 256M-aligned, you'll have to either use smaller pages or consider
that region to be "high"mem (assuming Linux supports highmem existing
below lowmem -- I'm skeptical).
+ /*
+ * For a kdump kernel, we may use a memory area reserved by the
boot
+ * kernel by using a kernel option like this
'crashkernel=32M@64M'.
+ * In this case, the ram is 96M. The kernel will try to map the
first
+ * 64M in the first tlb entry. The kernel will definitely get
stuck,
+ * since the kernel is running above the 64M. So we have to
make sure
+ * that the first tlb cover the current kernel running address
at least.
+ */
Maybe we should be running from AS1 when we set this up, to avoid
problems replacing an entry while it's in use?
Pardon my ignorance about how kdump/kexec works, but I'm a bit confused
by exactly what the situation is with crashkernel. How do we know that
we are the crash kernel, and that we should limit our RAM usage to that
area? I'm wondering if this code is assuming that the crashkernel area
is from where the kernel starts to the end of RAM.
+ while (1) {
+ cam_sz = calc_cam_sz(ram, virt, phys);
+ if (cam_sz + phys > PHYSICAL_START + _end - _stext)
+ break;
+ ram = 1 << (ilog2(ram) + 1);
+ }
The ram that was passed in is as much as you have. Don't map more.
What happens if (e.g.) memstart_addr is 512M, with a size of 512M, and
the kernel starts at 768M? Increasing the size will never get you a
mapping that covers kernstart, because calc_cam_sz will never return
more than 256M.
When does memory below the rounded-down kernel start get mapped?
-Scott
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
