Hi Oleksandr,
On 11/10/2021 18:48, Oleksandr Tyshchenko wrote:
---
tools/libs/light/libxl_arm.c | 76 ++++++++++++++++++++++++++++++++++++++++---
xen/include/public/arch-arm.h | 2 ++
2 files changed, 73 insertions(+), 5 deletions(-)
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index e3140a6..c0e8415 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -598,9 +598,20 @@ static int make_timer_node(libxl__gc *gc, void *fdt,
return 0;
}
+#define ALIGN_UP_TO_2MB(x) (((x) + MB(2) - 1) & (~(MB(2) - 1)))
+
static int make_hypervisor_node(libxl__gc *gc, void *fdt,
- const libxl_version_info *vers)
+ const libxl_version_info *vers,
+ const libxl_domain_build_info *b_info,
+ const struct xc_dom_image *dom)
{
+ uint64_t region_size[GUEST_RAM_BANKS] = {0}, region_base[GUEST_RAM_BANKS],
+ bank1end, ramsize;
+ uint32_t regs[(GUEST_ROOT_ADDRESS_CELLS + GUEST_ROOT_SIZE_CELLS) *
+ (GUEST_RAM_BANKS + 1)];
+ be32 *cells = ®s[0];
+ unsigned int i, len, nr_regions = 0;
+ libxl_dominfo info;
int res;
gic_interrupt intr;
@@ -615,9 +626,64 @@ static int make_hypervisor_node(libxl__gc *gc, void *fdt,
"xen,xen");
if (res) return res;
- /* reg 0 is grant table space */
- res = fdt_property_regs(gc, fdt, GUEST_ROOT_ADDRESS_CELLS,
GUEST_ROOT_SIZE_CELLS,
- 1,GUEST_GNTTAB_BASE, GUEST_GNTTAB_SIZE);
+ if (strcmp(dom->guest_type, "xen-3.0-aarch64")) {
+ LOG(WARN, "The extended regions are only supported for 64-bit guest
currently");
+ goto out;
+ }
I understand why we want to limit to 64-bit domain for dom0. But I am
not sure this is warrant for 32-bit domain. At worse, the guest will
ignore the bank because it is not usable. So could we drop the check?
+
+ res = libxl_domain_info(CTX, &info, dom->guest_domid);
+ if (res) return res;
+
+ assert(info.gpaddr_bits >= 32 && info.gpaddr_bits <= 48);
What could go wrong below if gpaddr_bits is not within this range?
+
+ /*
+ * Try to allocate separate 2MB-aligned extended regions from the first
+ * (below 4GB) and second (above 4GB) RAM banks taking into the account
+ * the maximum supported guest physical address space size and the amount
+ * of memory assigned to the guest.
+ * As the guest memory layout is not populated yet we cannot rely on
+ * dom->rambank_size[], so calculate the actual size of both banks using
+ * "max_memkb" value.
+ */
At the moment, libxl doesn't know how libxc will allocate the memory. We
may decide in the future to have only a small amount of memory below 4GB
and then the rest above 4GB. With this approach it would be more
difficult to modify the memory layout. Instead, I think we should create
a placeholder that is updated once we know the banks in
libxl__arch_domain_finalise_hw_description.
We also probably want to mention in the memory layout in
public/arch-arm.h this decision as the suggested way to find extended
regions will definitely impact our decision to re-order the memory
layout or shrink some regions in the future (I have in mind the PCI
Passthrough work).
+ ramsize = b_info->max_memkb * 1024;
+ if (ramsize <= GUEST_RAM0_SIZE) {
+ region_base[0] = GUEST_RAM0_BASE + ALIGN_UP_TO_2MB(ramsize);
+ region_size[0] = GUEST_RAM0_SIZE - ALIGN_UP_TO_2MB(ramsize);
+ region_base[1] = GUEST_RAM1_BASE;
+ } else
+ region_base[1] = GUEST_RAM1_BASE +
+ ALIGN_UP_TO_2MB(ramsize - GUEST_RAM0_SIZE);
+
+ bank1end = min(1ULL << info.gpaddr_bits, GUEST_RAM1_BASE +
GUEST_RAM1_SIZE);
+ if (bank1end > region_base[1])
+ region_size[1] = bank1end - region_base[1];
It would be best to not rely on the fact that Bank on is always below
4GB. If the code is too complex then we should look to add a
BUILD_BUG_ON() to avoid any surprise.
Cheers,
--
Julien Grall
