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Re: [PATCH V6 2/2] libxl/arm: Add handling of extended regions for DomU
On 13.10.21 18:15, Julien Grall wrote:
On 13/10/2021 14:46, Oleksandr wrote:
Hi Julien
Hi Oleksandr,
Hi Julien
Thank you for the prompt response.
On 13.10.21 00:43, Oleksandr wrote:
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index e3140a6..53ae0f3 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -615,9 +615,12 @@ static int make_hypervisor_node(libxl__gc *gc,
void *fdt,
"xen,xen");
if (res) return res;
- /* reg 0 is grant table space */
+ /*
+ * reg 0 is a placeholder for grant table space, reg 1...N are
+ * the placeholders for extended regions.
+ */
res = fdt_property_regs(gc, fdt, GUEST_ROOT_ADDRESS_CELLS,
GUEST_ROOT_SIZE_CELLS,
- 1,GUEST_GNTTAB_BASE, GUEST_GNTTAB_SIZE);
+ GUEST_RAM_BANKS + 1, 0, 0, 0, 0, 0, 0);
Here you are relying on GUEST_RAM_BANKS == 2. I think this is pretty
fragile as this may change in the future.
fdt_property_regs() is not really suitable for here. I would suggest
to create a new helper fdt_property_placeholder() which takes the
address cells, size cells and the number of ranges. The function will
then create N range that are zeroed.
You are right. Probably, we could add an assert here for now to be
triggered if "GUEST_RAM_BANKS != 2"?
But, if you still think we need to make it with the helper right now, I
will. However, I don't know how long this will take.
if (res) return res;
/*
@@ -1069,6 +1072,74 @@ static void finalise_one_node(libxl__gc *gc,
void *fdt, const char *uname,
}
}
+#define ALIGN_UP_TO_2MB(x) (((x) + MB(2) - 1) & (~(MB(2) - 1)))
+
+static void finalise_ext_region(libxl__gc *gc, struct xc_dom_image
*dom)
The function is doing more than finalizing extend regions, it also
create the grant table regs. So how about naming it:
finalize_hypervisor_node()?
ok, I don't mind.
+{
+ void *fdt = dom->devicetree_blob;
+ uint64_t region_size[GUEST_RAM_BANKS] = {0},
region_base[GUEST_RAM_BANKS],
+ bankend[GUEST_RAM_BANKS];
+ uint32_t regs[(GUEST_ROOT_ADDRESS_CELLS + GUEST_ROOT_SIZE_CELLS) *
+ (GUEST_RAM_BANKS + 1)];
+ be32 *cells = ®s[0];
+ const uint64_t bankbase[] = GUEST_RAM_BANK_BASES;
+ const uint64_t banksize[] = GUEST_RAM_BANK_SIZES;
+ unsigned int i, len, nr_regions = 0;
+ libxl_dominfo info;
+ int offset, rc;
+
+ offset = fdt_path_offset(fdt, "/hypervisor");
+ assert(offset > 0);
+
+ rc = libxl_domain_info(CTX, &info, dom->guest_domid);
+ assert(!rc);
+
+ assert(info.gpaddr_bits <= 64);
Neither of the two should be assert(). They should be proper check so
we don't end up with a disaster (in particularly for the former) if
there is a problem.
I looked at the similar finalise_*(), and it looks like no one bothers
with returning an error. Of course, this is not an excuse, will add a
proper check.
+
+ /*
+ * Try to allocate separate 2MB-aligned extended regions from
the first
+ * and second RAM banks taking into the account the maximum
supported
+ * guest physical address space size and the amount of memory
assigned
+ * to the guest.
+ */
+ for (i = 0; i < GUEST_RAM_BANKS; i++) {
+ region_base[i] = bankbase[i] +
+ ALIGN_UP_TO_2MB((uint64_t)dom->rambank_size[i] <<
XC_PAGE_SHIFT);
+
+ bankend[i] = ~0ULL >> (64 - info.gpaddr_bits);
+ bankend[i] = min(bankend[i], bankbase[i] + banksize[i] - 1);
+ if (bankend[i] > region_base[i])
+ region_size[i] = bankend[i] - region_base[i] + 1;
+ } > +
+ /*
+ * The region 0 for grant table space must be always present. If
we managed
+ * to allocate the extended regions then insert them as regions
1...N.
+ */
+ set_range(&cells, GUEST_ROOT_ADDRESS_CELLS, GUEST_ROOT_SIZE_CELLS,
+ GUEST_GNTTAB_BASE, GUEST_GNTTAB_SIZE);
+
+ for (i = 0; i < GUEST_RAM_BANKS; i++) {
+ if (region_size[i] < GUEST_EXT_REGION_MIN_SIZE)
+ continue;
+
+ LOG(DEBUG, "Extended region %u: %#"PRIx64"->%#"PRIx64"",
+ nr_regions, region_base[i], region_base[i] +
region_size[i]);
+
+ set_range(&cells, GUEST_ROOT_ADDRESS_CELLS,
GUEST_ROOT_SIZE_CELLS,
+ region_base[i], region_size[i]);
+ nr_regions++;
+ }
+
+ if (!nr_regions)
+ LOG(WARN, "The extended regions cannot be allocated, not
enough space");
+
+ len = sizeof(regs[0]) * (GUEST_ROOT_ADDRESS_CELLS +
GUEST_ROOT_SIZE_CELLS) *
+ (nr_regions + 1);
+ rc = fdt_setprop(fdt, offset, "reg", regs, len);
+ assert(!rc);
We should propagate the error.
ok, will propagate, it looks like an upper layer
libxl__arch_domain_finalise_hw_description() also needs to propagate it.
+}
+
int libxl__arch_domain_finalise_hw_description(libxl__gc *gc,
uint32_t domid,
libxl_domain_config *d_config,
@@ -1109,6 +1180,8 @@ int
libxl__arch_domain_finalise_hw_description(libxl__gc *gc,
}
+ finalise_ext_region(gc, dom);
+
for (i = 0; i < GUEST_RAM_BANKS; i++) {
const uint64_t size = (uint64_t)dom->rambank_size[i] <<
XC_PAGE_SHIFT;
diff --git a/xen/include/public/arch-arm.h
b/xen/include/public/arch-arm.h
index d46c61f..7425a78 100644
--- a/xen/include/public/arch-arm.h
+++ b/xen/include/public/arch-arm.h
@@ -438,6 +438,11 @@ typedef uint64_t xen_callback_t;
#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(0x40000000) /* 3GB of low
RAM @ 1GB */
#define GUEST_RAM0_SIZE xen_mk_ullong(0xc0000000)
@@ -451,6 +456,8 @@ typedef uint64_t xen_callback_t;
#define GUEST_RAM_BANK_BASES { GUEST_RAM0_BASE, GUEST_RAM1_BASE }
#define GUEST_RAM_BANK_SIZES { GUEST_RAM0_SIZE, GUEST_RAM1_SIZE }
+#define GUEST_EXT_REGION_MIN_SIZE xen_mk_ullong(0x0004000000) /*
64MB */
I would prefer if this value is not part of the public header because
this is not a value that the hypervisor needs to know. So it is better
to restrict it to the libxl_arm.c
ok, will do.
--
Regards,
Oleksandr Tyshchenko
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