[PATCH v3 11/12] xen/riscv: add definition of guest RAM banks

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

The dom0less solution uses defined RAM banks as compile-time constants,
so introduce macros to describe guest RAM banks.

The reason for 2 banks is that there is typically always a use case for
low memory under 4 GB, but the bank under 4 GB ends up being small because
there are other things under 4 GB it can conflict with (interrupt
controller, PCI BARs, etc.). So a second bank is added above that MMIO
region (starting at 8 GiB) to provide the remaining RAM; the gap between
the two banks also exercises code paths handling discontiguous memory.
For Sv32 guests (34-bit GPA, 16 GiB addressable), bank0 provides 2 GB
(2–4 GB) and the first 8 GB of bank1 (8–16 GB) is accessible.

Extended regions are useful for RISC-V: they could be used to provide a
"space" for Linux to map grant mappings.

Despite the fact that for every guest MMU mode the GPA could be up
to 56 bits wide (except Sv32 whose GPA is 34 bits), the combined size
of both banks is limited to 1018 GB as it is more than enough for most
use cases.

Add inclusion of asm/guest-layout.h to asm/domain.h to make dom0less
common code build happy.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v3:
 - Move GUEST_RAM*-related defines to asm/p2m.h instead of public header.
---
Changes in v2:
 - New patch.
---
 xen/arch/riscv/include/asm/domain.h       |  1 +
 xen/arch/riscv/include/asm/guest-layout.h | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 xen/arch/riscv/include/asm/guest-layout.h

diff --git a/xen/arch/riscv/include/asm/domain.h 
b/xen/arch/riscv/include/asm/domain.h
index 6c48bf13111d..6044ce0feee0 100644
--- a/xen/arch/riscv/include/asm/domain.h
+++ b/xen/arch/riscv/include/asm/domain.h
@@ -7,6 +7,7 @@
 #include <xen/xmalloc.h>
 #include <public/hvm/params.h>
 
+#include <asm/guest-layout.h>
 #include <asm/p2m.h>
 #include <asm/vtimer.h>
 
diff --git a/xen/arch/riscv/include/asm/guest-layout.h 
b/xen/arch/riscv/include/asm/guest-layout.h
new file mode 100644
index 000000000000..68d95a09394c
--- /dev/null
+++ b/xen/arch/riscv/include/asm/guest-layout.h
@@ -0,0 +1,23 @@
+#ifndef ASM_RISCV_GUEST_LAYOUT_H
+#define ASM_RISCV_GUEST_LAYOUT_H
+
+#include <public/xen.h>
+
+#define GUEST_RAM_BANKS   2
+
+/*
+ * The way to find the extended regions (to be exposed to the guest as unused
+ * address space) relies on the fact that the regions reserved for the RAM
+ * below are big enough to also accommodate such regions.
+ */
+#define GUEST_RAM0_BASE   xen_mk_ullong(0x80000000) /* 2GB of low RAM @ 2GB */
+#define GUEST_RAM0_SIZE   xen_mk_ullong(0x80000000)
+
+#define GUEST_RAM1_BASE   xen_mk_ullong(0x0200000000) /* 1016 GB of RAM @ 8GB 
*/
+#define GUEST_RAM1_SIZE   xen_mk_ullong(0xFE00000000)
+
+/* TODO: allocate these all dynamically */
+#define GUEST_RAM_BANK_BASES   { GUEST_RAM0_BASE, GUEST_RAM1_BASE }
+#define GUEST_RAM_BANK_SIZES   { GUEST_RAM0_SIZE, GUEST_RAM1_SIZE }
+
+#endif /* ASM_RISCV_GUEST_LAYOUT_H */
-- 
2.53.0