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Re: [PATCH v5 7/8] xen/arm: create shared memory nodes in guest device tree
Hi Penny,
On 20/06/2022 06:11, Penny Zheng wrote:
We expose the shared memory to the domU using the "xen,shared-memory-v1"
reserved-memory binding. See
Documentation/devicetree/bindings/reserved-memory/xen,shared-memory.txt
in Linux for the corresponding device tree binding.
To save the cost of re-parsing shared memory device tree configuration when
creating shared memory nodes in guest device tree, this commit adds new field
"shm_mem" to store shm-info per domain.
For each shared memory region, a range is exposed under
the /reserved-memory node as a child node. Each range sub-node is
named xen-shmem@<address> and has the following properties:
- compatible:
compatible = "xen,shared-memory-v1"
- reg:
the base guest physical address and size of the shared memory region
- xen,id:
a string that identifies the shared memory region.
Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
v5 change:
- no change
---
v4 change:
- no change
---
v3 change:
- move field "shm_mem" to kernel_info
---
v2 change:
- using xzalloc
- shm_id should be uint8_t
- make reg a local variable
- add #address-cells and #size-cells properties
- fix alignment
---
xen/arch/arm/domain_build.c | 143 +++++++++++++++++++++++++++++-
xen/arch/arm/include/asm/kernel.h | 1 +
xen/arch/arm/include/asm/setup.h | 1 +
3 files changed, 143 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 1584e6c2ce..4d62440a0e 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -900,7 +900,22 @@ static int __init allocate_shared_memory(struct domain *d,
return ret;
}
-static int __init process_shm(struct domain *d,
+static int __init append_shm_bank_to_domain(struct kernel_info *kinfo,
+ paddr_t start, paddr_t size,
+ u32 shm_id)
+{
+ if ( (kinfo->shm_mem.nr_banks + 1) > NR_MEM_BANKS )
+ return -ENOMEM;
+
+ kinfo->shm_mem.bank[kinfo->shm_mem.nr_banks].start = start;
+ kinfo->shm_mem.bank[kinfo->shm_mem.nr_banks].size = size;
+ kinfo->shm_mem.bank[kinfo->shm_mem.nr_banks].shm_id = shm_id;
+ kinfo->shm_mem.nr_banks++;
+
+ return 0;
+}
+
+static int __init process_shm(struct domain *d, struct kernel_info *kinfo,
const struct dt_device_node *node)
{
struct dt_device_node *shm_node;
@@ -971,6 +986,14 @@ static int __init process_shm(struct domain *d,
if ( ret )
return ret;
}
+
+ /*
+ * Record static shared memory region info for later setting
+ * up shm-node in guest device tree.
+ */
+ ret = append_shm_bank_to_domain(kinfo, gbase, psize, shm_id);
+ if ( ret )
+ return ret;
}
return 0;
@@ -1301,6 +1324,117 @@ static int __init make_memory_node(const struct domain
*d,
return res;
}
+#ifdef CONFIG_STATIC_SHM
+static int __init make_shm_memory_node(const struct domain *d,
+ void *fdt,
+ int addrcells, int sizecells,
+ struct meminfo *mem)
NIT: AFAICT mem is not changed, so it should be const.
+{
+ unsigned long i = 0;
NIT: This should be "unsigned int" to match the type of nr_banks.
+ int res = 0;
+
+ if ( mem->nr_banks == 0 )
+ return -ENOENT;
+
+ /*
+ * For each shared memory region, a range is exposed under
+ * the /reserved-memory node as a child node. Each range sub-node is
+ * named xen-shmem@<address>.
+ */
+ dt_dprintk("Create xen-shmem node\n");
+
+ for ( ; i < mem->nr_banks; i++ )
+ {
+ uint64_t start = mem->bank[i].start;
+ uint64_t size = mem->bank[i].size;
+ uint8_t shm_id = mem->bank[i].shm_id;
+ /* Placeholder for xen-shmem@ + a 64-bit number + \0 */
+ char buf[27];
+ const char compat[] = "xen,shared-memory-v1";
+ __be32 reg[4];
+ __be32 *cells;
+ unsigned int len = (addrcells + sizecells) * sizeof(__be32);
+
+ snprintf(buf, sizeof(buf), "xen-shmem@%"PRIx64, mem->bank[i].start);
+ res = fdt_begin_node(fdt, buf);
+ if ( res )
+ return res;
+
+ res = fdt_property(fdt, "compatible", compat, sizeof(compat));
+ if ( res )
+ return res;
+
+ cells = reg;
+ dt_child_set_range(&cells, addrcells, sizecells, start, size);
+
+ res = fdt_property(fdt, "reg", reg, len);
+ if ( res )
+ return res;
+
+ dt_dprintk("Shared memory bank %lu: %#"PRIx64"->%#"PRIx64"\n",
+ i, start, start + size);
+
+ res = fdt_property_cell(fdt, "xen,id", shm_id);
Looking at the Linux binding, "xen,id" is meant to be a string. But here
you are writing it as an integer.
Given that the Linux binding is already merged, I think the Xen binding
should be changed.
+ if ( res )
+ return res;
+
+ res = fdt_end_node(fdt);
+ if ( res )
+ return res;
+ }
+
+ return res;
+}
+#else
+static int __init make_shm_memory_node(const struct domain *d,
+ void *fdt,
+ int addrcells, int sizecells,
+ struct meminfo *mem)
+{
+ ASSERT_UNREACHABLE();
+}
+#endif
+
+static int __init make_resv_memory_node(const struct domain *d,
+ void *fdt,
+ int addrcells, int sizecells,
+ struct meminfo *mem)
+{
+ int res = 0;
+ /* Placeholder for reserved-memory\0 */
+ char resvbuf[16] = "reserved-memory";
+
+ if ( mem->nr_banks == 0 )
+ /* No shared memory provided. */
+ return 0;
+
+ dt_dprintk("Create reserved-memory node\n");
+
+ res = fdt_begin_node(fdt, resvbuf);
+ if ( res )
+ return res;
+
+ res = fdt_property(fdt, "ranges", NULL, 0);
+ if ( res )
+ return res;
+
+ res = fdt_property_cell(fdt, "#address-cells", addrcells);
+ if ( res )
+ return res;
+
+ res = fdt_property_cell(fdt, "#size-cells", sizecells);
+ if ( res )
+ return res;
+
+ res = make_shm_memory_node(d, fdt, addrcells, sizecells, mem);
+ if ( res )
+ return res;
+
+ res = fdt_end_node(fdt);
+
+ return res;
+}
+
static int __init add_ext_regions(unsigned long s, unsigned long e, void
*data)
{
struct meminfo *ext_regions = data;
@@ -3078,6 +3212,11 @@ static int __init prepare_dtb_domU(struct domain *d,
struct kernel_info *kinfo)
if ( ret )
goto err;
+ ret = make_resv_memory_node(d, kinfo->fdt, addrcells, sizecells,
+ &kinfo->shm_mem);
+ if ( ret )
+ goto err;
+
/*
* domain_handle_dtb_bootmodule has to be called before the rest of
* the device tree is generated because it depends on the value of
@@ -3454,7 +3593,7 @@ static int __init construct_domU(struct domain *d,
assign_static_memory_11(d, &kinfo, node);
#ifdef CONFIG_STATIC_SHM
- rc = process_shm(d, node);
+ rc = process_shm(d, &kinfo, node);
if ( rc < 0 )
return rc;
#endif
diff --git a/xen/arch/arm/include/asm/kernel.h
b/xen/arch/arm/include/asm/kernel.h
index c4dc039b54..2cc506b100 100644
--- a/xen/arch/arm/include/asm/kernel.h
+++ b/xen/arch/arm/include/asm/kernel.h
@@ -19,6 +19,7 @@ struct kernel_info {
void *fdt; /* flat device tree */
paddr_t unassigned_mem; /* RAM not (yet) assigned to a bank */
struct meminfo mem;
+ struct meminfo shm_mem;
/* kernel entry point */
paddr_t entry;
diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
index 5063e5d077..7497cc40aa 100644
--- a/xen/arch/arm/include/asm/setup.h
+++ b/xen/arch/arm/include/asm/setup.h
@@ -29,6 +29,7 @@ struct membank {
bool xen_domain; /* whether the memory bank is bound to a Xen domain. */
#ifdef CONFIG_STATIC_SHM
unsigned int nr_shm_domain;
+ uint8_t shm_id ; /* ID identifier of a static shared memory bank. */
I am not entirely happy that we are defining shm_id for everyone. We are
at v5, so I am OK for now.
But I would at least like "shm_id" to be defined before nr_shm_domain so
we re-use the existing hole and avoid increasing the size of the structure.
Cheers,
--
Julien Grall
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