[PATCH v2 06/17] xen/riscv: add root page table allocation

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Introduce support for allocating and initializing the root page table
required for RISC-V stage-2 address translation.

To implement root page table allocation the following is introduced:
- p2m_get_clean_page() and p2m_allocate_root() helpers to allocate and
  zero a 16 KiB root page table, as mandated by the RISC-V privileged
  specification for Sv39x4/Sv48x4 modes.
- Add hgatp_from_page() to construct the hgatp register value from the
  allocated root page.
- Update p2m_init() to allocate the root table and initialize
  p2m->root and p2m->hgatp.
- Add maddr_to_page() and page_to_maddr() macros for easier address
  manipulation.
- Allocate root p2m table after p2m pool is initialized.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v2:
 - This patch was created from "xen/riscv: introduce things necessary for p2m
   initialization" with the following changes:
   - [clear_and_clean_page()] Add missed call of clean_dcache_va_range().
   - Drop p2m_get_clean_page() as it is going to be used only once to allocate
     root page table. Open-code it explicittly in p2m_allocate_root(). Also,
     it will help avoid duplication of the code connected to order and nr_pages
     of p2m root page table.
   - Instead of using order 2 for alloc_domheap_pages(), use
     get_order_from_bytes(KB(16)).
   - Clear and clean a proper amount of allocated pages in p2m_allocate_root().
   - Drop _info from the function name hgatp_from_page_info() and its argument
     page_info.
   - Introduce HGATP_MODE_MASK and use MASK_INSR() instead of shift to calculate
     value of hgatp.
   - Drop unnecessary parentheses in definition of page_to_maddr().
   - Add support of VMID.
   - Drop TLB flushing in p2m_alloc_root_table() and do that once when VMID
     is re-used. [Look at p2m_alloc_vmid()]
   - Allocate p2m root table after p2m pool is fully initialized: first
     return pages to p2m pool them allocate p2m root table.
---
 xen/arch/riscv/include/asm/mm.h             |  4 +
 xen/arch/riscv/include/asm/p2m.h            |  6 ++
 xen/arch/riscv/include/asm/riscv_encoding.h |  4 +
 xen/arch/riscv/p2m.c                        | 94 +++++++++++++++++++++
 4 files changed, 108 insertions(+)

diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 01bbd92a06..912bc79e1b 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -149,6 +149,10 @@ extern struct page_info *frametable_virt_start;
 #define mfn_to_page(mfn)    (frametable_virt_start + mfn_x(mfn))
 #define page_to_mfn(pg)     _mfn((pg) - frametable_virt_start)
 
+/* Convert between machine addresses and page-info structures. */
+#define maddr_to_page(ma) mfn_to_page(maddr_to_mfn(ma))
+#define page_to_maddr(pg) mfn_to_maddr(page_to_mfn(pg))
+
 static inline void *page_to_virt(const struct page_info *pg)
 {
     return mfn_to_virt(mfn_x(page_to_mfn(pg)));
diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
index 9570eff014..a31b05bd50 100644
--- a/xen/arch/riscv/include/asm/p2m.h
+++ b/xen/arch/riscv/include/asm/p2m.h
@@ -26,6 +26,12 @@ struct p2m_domain {
     /* Pages used to construct the p2m */
     struct page_list_head pages;
 
+    /* The root of the p2m tree. May be concatenated */
+    struct page_info *root;
+
+    /* Address Translation Table for the p2m */
+    paddr_t hgatp;
+
     /* Indicate if it is required to clean the cache when writing an entry */
     bool clean_pte;
 
diff --git a/xen/arch/riscv/include/asm/riscv_encoding.h 
b/xen/arch/riscv/include/asm/riscv_encoding.h
index 6cc8f4eb45..a71b7546ef 100644
--- a/xen/arch/riscv/include/asm/riscv_encoding.h
+++ b/xen/arch/riscv/include/asm/riscv_encoding.h
@@ -133,11 +133,13 @@
 #define HGATP_MODE_SV48X4              _UL(9)
 
 #define HGATP32_MODE_SHIFT             31
+#define HGATP32_MODE_MASK              _UL(0x80000000)
 #define HGATP32_VMID_SHIFT             22
 #define HGATP32_VMID_MASK              _UL(0x1FC00000)
 #define HGATP32_PPN                    _UL(0x003FFFFF)
 
 #define HGATP64_MODE_SHIFT             60
+#define HGATP64_MODE_MASK              _ULL(0xF000000000000000)
 #define HGATP64_VMID_SHIFT             44
 #define HGATP64_VMID_MASK              _ULL(0x03FFF00000000000)
 #define HGATP64_PPN                    _ULL(0x00000FFFFFFFFFFF)
@@ -170,6 +172,7 @@
 #define HGATP_VMID_SHIFT               HGATP64_VMID_SHIFT
 #define HGATP_VMID_MASK                        HGATP64_VMID_MASK
 #define HGATP_MODE_SHIFT               HGATP64_MODE_SHIFT
+#define HGATP_MODE_MASK                        HGATP64_MODE_MASK
 #else
 #define MSTATUS_SD                     MSTATUS32_SD
 #define SSTATUS_SD                     SSTATUS32_SD
@@ -181,6 +184,7 @@
 #define HGATP_VMID_SHIFT               HGATP32_VMID_SHIFT
 #define HGATP_VMID_MASK                        HGATP32_VMID_MASK
 #define HGATP_MODE_SHIFT               HGATP32_MODE_SHIFT
+#define HGATP_MODE_MASK                        HGATP32_MODE_MASK
 #endif
 
 #define TOPI_IID_SHIFT                 16
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index e409997499..2419a61d8c 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -41,6 +41,91 @@ void p2m_write_unlock(struct p2m_domain *p2m)
     write_unlock(&p2m->lock);
 }
 
+static void clear_and_clean_page(struct page_info *page)
+{
+    clean_dcache_va_range(page, PAGE_SIZE);
+    clear_domain_page(page_to_mfn(page));
+}
+
+static struct page_info *p2m_allocate_root(struct domain *d)
+{
+    struct page_info *page;
+    unsigned int order = get_order_from_bytes(KB(16));
+    unsigned int nr_pages = _AC(1,U) << order;
+
+    /* Return back nr_pages necessary for p2m root table. */
+
+    if ( ACCESS_ONCE(d->arch.paging.p2m_total_pages) < nr_pages )
+        panic("Specify more xen,domain-p2m-mem-mb\n");
+
+    for ( unsigned int i = 0; i < nr_pages; i++ )
+    {
+        /* Return memory to domheap. */
+        page = page_list_remove_head(&d->arch.paging.p2m_freelist);
+        if( page )
+        {
+            ACCESS_ONCE(d->arch.paging.p2m_total_pages)--;
+            free_domheap_page(page);
+        }
+        else
+        {
+            printk(XENLOG_ERR
+                   "Failed to free P2M pages, P2M freelist is empty.\n");
+            return NULL;
+        }
+    }
+
+    /* Allocate memory for p2m root table. */
+
+    /*
+     * As mentioned in the Priviliged Architecture Spec (version 20240411)
+     * As explained in Section 18.5.1, for the paged virtual-memory schemes
+     * (Sv32x4, Sv39x4, Sv48x4, and Sv57x4), the root page table is 16 KiB
+     * and must be aligned to a 16-KiB boundary.
+     */
+    page = alloc_domheap_pages(d, order, MEMF_no_owner);
+    if ( page == NULL )
+        return NULL;
+
+    for ( unsigned int i = 0; i < nr_pages; i++ )
+        clear_and_clean_page(page + i);
+
+    return page;
+}
+
+static unsigned long hgatp_from_page(struct p2m_domain *p2m)
+{
+    struct page_info *p2m_root_page = p2m->root;
+    unsigned long ppn;
+    unsigned long hgatp_mode;
+
+    ppn = PFN_DOWN(page_to_maddr(p2m_root_page)) & HGATP_PPN;
+
+#if RV_STAGE1_MODE == SATP_MODE_SV39
+    hgatp_mode = HGATP_MODE_SV39X4;
+#elif RV_STAGE1_MODE == SATP_MODE_SV48
+    hgatp_mode = HGATP_MODE_SV48X4;
+#else
+#   error "add HGATP_MODE"
+#endif
+
+    return ppn | MASK_INSR(p2m->vmid, HGATP_VMID_MASK) |
+           MASK_INSR(hgatp_mode, HGATP_MODE_MASK);
+}
+
+static int p2m_alloc_root_table(struct domain *d)
+{
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+
+    p2m->root = p2m_allocate_root(d);
+    if ( !p2m->root )
+        return -ENOMEM;
+
+    p2m->hgatp = hgatp_from_page(p2m);
+
+    return 0;
+}
+
 static spinlock_t vmid_alloc_lock = SPIN_LOCK_UNLOCKED;
 
 /*
@@ -228,5 +313,14 @@ int p2m_set_allocation(struct domain *d, unsigned long 
pages, bool *preempted)
         }
     }
 
+    /*
+    * First, wait for the p2m pool to be initialized. Then allocate the root
+    * table so that the necessary pages can be returned from the p2m pool,
+    * since the root table must be allocated using alloc_domheap_pages(...)
+    * to meet its specific requirements.
+    */
+    if ( !d->arch.p2m.root )
+        p2m_alloc_root_table(d);
+
     return 0;
 }
-- 
2.49.0