[PATCH v6 04/23] xen/riscv: Implement ARCH_PAGING_MEMPOOL

The p2m_freelist is used to allocate pages for the P2M. To initialize
this list, domain_p2m_set_allocation() may be called from construct_domU()
in the common Dom0less code, so RISC-V provides an implementation and
enables CONFIG_ARCH_PAGING_MEMPOOL unconditionally.

Additionally, implement arch_{set,get}_paging_mempool_size(). They are
not directly used yet, but are required to support the
XEN_DOMCTL_{get,set}_paging_mempool_size hypercalls.

Signed-off-by: Oleksii Kurochko <[email protected]>
Acked-by: Jan Beulich <[email protected]>
---
Changes in v4-v6:
 - Nothing changed. Only rebase.
---
Changes in v3:
 - Drop stray blank space in arch_get_paging_mempool_size().
 - Add Acked-by: Jan Beulich <[email protected]>.
---
Changes in v2:
 - Turn on CONFIG_ARCH_PAGING_MEMPOOL=y unconditionally and drop all ifdef-s
   related to this config.
 - Optimize check inside arch_set_paging_mempool_size which verify size
   argument.
 - Use pfn_to_paddr() inside arch_get_paging_mempool_size() instead of open
   coding the stuff.
 - Drop ASSERT() from arch_set_paging_mempool_size() as it is impossible to
   have here preempted = true and rc != -ERESTART.
---
---
 xen/arch/riscv/Kconfig |  1 +
 xen/arch/riscv/p2m.c   | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/xen/arch/riscv/Kconfig b/xen/arch/riscv/Kconfig
index 41426c205292..48520588fe40 100644
--- a/xen/arch/riscv/Kconfig
+++ b/xen/arch/riscv/Kconfig
@@ -1,5 +1,6 @@
 config RISCV
 	def_bool y
+	select ARCH_PAGING_MEMPOOL
 	select DOMAIN_BUILD_HELPERS
 	select FUNCTION_ALIGNMENT_16B
 	select GENERIC_BUG_FRAME
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index 566266e3e78f..1cea86512c8c 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -1600,3 +1600,27 @@ struct page_info *get_page_from_gfn(struct domain *d, unsigned long gfn,
 
     return p2m_get_page_from_gfn(p2m_get_hostp2m(d), _gfn(gfn), t);
 }
+
+int arch_set_paging_mempool_size(struct domain *d, uint64_t size)
+{
+    unsigned long pages = PFN_DOWN(size);
+    int rc;
+
+    /* Non page-sized request or 32-bit overflow? */
+    if ( pfn_to_paddr(pages) != size )
+        return -EINVAL;
+
+    spin_lock(&d->arch.paging.lock);
+    rc = p2m_set_allocation(d, pages, true);
+    spin_unlock(&d->arch.paging.lock);
+
+    return rc;
+}
+
+/* Return the size of the pool, in bytes. */
+int arch_get_paging_mempool_size(struct domain *d, uint64_t *size)
+{
+    *size = pfn_to_paddr(ACCESS_ONCE(d->arch.paging.total_pages));
+
+    return 0;
+}
-- 
2.54.0