On 5/17/21 7:43 PM, Bob Eshleman wrote:
On 5/14/21 4:47 PM, Connor Davis wrote:
On 5/14/21 3:53 PM, Bob Eshleman wrote:
On 5/14/21 11:53 AM, Connor Davis wrote:
+
+#ifdef CONFIG_RISCV_64
+
+/*
+ * RISC-V Layout:
+ * 0x0000000000000000 - 0x0000003fffffffff (256GB, L2 slots [0-255])
+ * Unmapped
+ * 0x0000004000000000 - 0xffffffbfffffffff
+ * Inaccessible: sv39 only supports 39-bit sign-extended VAs.
+ * 0xffffffc000000000 - 0xffffffc0001fffff (2MB, L2 slot [256])
+ * Unmapped
+ * 0xffffffc000200000 - 0xffffffc0003fffff (2MB, L2 slot [256])
+ * Xen text, data, bss
+ * 0xffffffc000400000 - 0xffffffc0005fffff (2MB, L2 slot [256])
+ * Fixmap: special-purpose 4K mapping slots
+ * 0xffffffc000600000 - 0xffffffc0009fffff (4MB, L2 slot [256])
+ * Early boot mapping of FDT
+ * 0xffffffc000a00000 - 0xffffffc000bfffff (2MB, L2 slot [256])
+ * Early relocation address, used when relocating Xen and later
+ * for livepatch vmap (if compiled in)
+ * 0xffffffc040000000 - 0xffffffc07fffffff (1GB, L2 slot [257])
+ * VMAP: ioremap and early_ioremap
+ * 0xffffffc080000000 - 0xffffffc13fffffff (3GB, L2 slots [258..260])
+ * Unmapped
+ * 0xffffffc140000000 - 0xffffffc1bfffffff (2GB, L2 slots [261..262])
+ * Frametable: 48 bytes per page for 133GB of RAM
+ * 0xffffffc1c0000000 - 0xffffffe1bfffffff (128GB, L2 slots [263..390])
+ * 1:1 direct mapping of RAM
+ * 0xffffffe1c0000000 - 0xffffffffffffffff (121GB, L2 slots [391..511])
+ * Unmapped
+ */
+
What is the benefit of moving the layout up to 0xffffffc000000000?
I thought it made the most sense to use the upper half since Xen is privileged
and privileged code is typically mapped in the upper half, at least on x86. I'm
happy to
move it down if that would be preferred.
I do like the idea of following norms, but I think I prefer following the ARM
norm
over the x86 norm unless there is a technical reason not to. Just due to
ARM and RISC-V having much more overlap than x86 and RISC-V. In this case,
all things being equal, I'd prefer following the ARM model and use the lower
half.
I definitely like adding the note on the inaccessible region.
Sounds good, I will move it down.
Thanks,
Connor