Implement map_pages_to_xen() which requires several
functions to manage page tables and entries:
- pt_update()
- pt_mapping_level()
- pt_update_entry()
- pt_next_level()
- pt_check_entry()
To support these operations, add functions for creating,
mapping, and unmapping Xen tables:
- create_table()
- map_table()
- unmap_table()
Introduce PTE_SMALL to indicate that 4KB mapping is needed
and PTE_POPULATE.
In addition introduce flush_tlb_range_va() for TLB flushing across
CPUs after updating the PTE for the requested mapping.
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
xen/arch/riscv/Makefile | 1 +
xen/arch/riscv/include/asm/flushtlb.h | 9 +
xen/arch/riscv/include/asm/mm.h | 2 +
xen/arch/riscv/include/asm/page.h | 80 ++++
xen/arch/riscv/include/asm/riscv_encoding.h | 2 +
xen/arch/riscv/mm.c | 9 -
xen/arch/riscv/pt.c | 421 ++++++++++++++++++++
7 files changed, 515 insertions(+), 9 deletions(-)
create mode 100644 xen/arch/riscv/pt.c
diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 6832549133..a5eb2aed4b 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -1,6 +1,7 @@
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-y += entry.o
obj-y += mm.o
+obj-y += pt.o
obj-$(CONFIG_RISCV_64) += riscv64/
obj-y += sbi.o
obj-y += setup.o
diff --git a/xen/arch/riscv/include/asm/flushtlb.h b/xen/arch/riscv/include/asm/flushtlb.h
index f4a735fd6c..43214f5e95 100644
--- a/xen/arch/riscv/include/asm/flushtlb.h
+++ b/xen/arch/riscv/include/asm/flushtlb.h
@@ -5,12 +5,21 @@
#include <xen/bug.h>
#include <xen/cpumask.h>
+#include <asm/sbi.h>
+
/* Flush TLB of local processor for address va. */
static inline void flush_tlb_one_local(vaddr_t va)
{
asm volatile ( "sfence.vma %0" :: "r" (va) : "memory" );
}
+/* Flush a range of VA's hypervisor mappings from the TLB of all processors. */
+static inline void flush_tlb_range_va(vaddr_t va, size_t size)
+{
+ BUG_ON(!sbi_has_rfence());
+ sbi_remote_sfence_vma(NULL, va, size);
+}
+
/*
* Filter the given set of CPUs, removing those that definitely flushed their
* TLB since @page_timestamp.
diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index a0bdc2bc3a..ce1557bb27 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -42,6 +42,8 @@ static inline void *maddr_to_virt(paddr_t ma)
#define virt_to_mfn(va) __virt_to_mfn(va)
#define mfn_to_virt(mfn) __mfn_to_virt(mfn)
+#define mfn_from_pte(pte) maddr_to_mfn(pte_to_paddr(pte))
+
struct page_info
{
/* Each frame can be threaded onto a doubly-linked list. */
diff --git a/xen/arch/riscv/include/asm/page.h b/xen/arch/riscv/include/asm/page.h
index eb79cb9409..89fa290697 100644
--- a/xen/arch/riscv/include/asm/page.h
+++ b/xen/arch/riscv/include/asm/page.h
@@ -21,6 +21,11 @@
#define XEN_PT_LEVEL_MAP_MASK(lvl) (~(XEN_PT_LEVEL_SIZE(lvl) - 1))
#define XEN_PT_LEVEL_MASK(lvl) (VPN_MASK << XEN_PT_LEVEL_SHIFT(lvl))
+/*
+ * PTE format:
+ * | XLEN-1 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
+ * PFN reserved for SW D A G U X W R V
+ */
#define PTE_VALID BIT(0, UL)
#define PTE_READABLE BIT(1, UL)
#define PTE_WRITABLE BIT(2, UL)
@@ -34,15 +39,49 @@
#define PTE_LEAF_DEFAULT (PTE_VALID | PTE_READABLE | PTE_WRITABLE)
#define PTE_TABLE (PTE_VALID)
+#define PAGE_HYPERVISOR_RO (PTE_VALID | PTE_READABLE)
#define PAGE_HYPERVISOR_RW (PTE_VALID | PTE_READABLE | PTE_WRITABLE)
+#define PAGE_HYPERVISOR_RX (PTE_VALID | PTE_READABLE | PTE_EXECUTABLE)
#define PAGE_HYPERVISOR PAGE_HYPERVISOR_RW
+/*
+ * The PTE format does not contain the following bits within itself;
+ * they are created artificially to inform the Xen page table
+ * handling algorithm. These bits should not be explicitly written
+ * to the PTE entry.
+ */
+#define PTE_SMALL BIT(10, UL)
+#define PTE_POPULATE BIT(11, UL)
+
+#define PTE_ACCESS_MASK (PTE_READABLE | PTE_WRITABLE | PTE_EXECUTABLE)
+
/* Calculate the offsets into the pagetables for a given VA */
#define pt_linear_offset(lvl, va) ((va) >> XEN_PT_LEVEL_SHIFT(lvl))
#define pt_index(lvl, va) (pt_linear_offset((lvl), (va)) & VPN_MASK)
+#define PAGETABLE_ORDER_MASK ((_AC(1, U) << PAGETABLE_ORDER) - 1)
+#define TABLE_OFFSET(offs) (_AT(unsigned int, offs) & PAGETABLE_ORDER_MASK)
+
+#if RV_STAGE1_MODE > SATP_MODE_SV39
+#error "need to to update DECLARE_OFFSETS macros"
+#else
+
+#define l0_table_offset(va) TABLE_OFFSET(pt_linear_offset(0, va))
+#define l1_table_offset(va) TABLE_OFFSET(pt_linear_offset(1, va))
+#define l2_table_offset(va) TABLE_OFFSET(pt_linear_offset(2, va))
+
+/* Generate an array @var containing the offset for each level from @addr */
+#define DECLARE_OFFSETS(var, addr) \
+ const unsigned int var[] = { \
+ l0_table_offset(addr), \
+ l1_table_offset(addr), \
+ l2_table_offset(addr), \
+ }
+
+#endif
+
/* Page Table entry */
typedef struct {
#ifdef CONFIG_RISCV_64
@@ -68,6 +107,47 @@ static inline bool pte_is_valid(pte_t p)
return p.pte & PTE_VALID;
}
+/*
+ * From the RISC-V spec:
+ * The V bit indicates whether the PTE is valid; if it is 0, all other bits
+ * in the PTE are don’t-cares and may be used freely by software.
+ *
+ * If V=1 the encoding of PTE R/W/X bits could be find in "the encoding
+ * of the permission bits" table.
+ *
+ * The encoding of the permission bits table:
+ * X W R Meaning
+ * 0 0 0 Pointer to next level of page table.
+ * 0 0 1 Read-only page.
+ * 0 1 0 Reserved for future use.
+ * 0 1 1 Read-write page.
+ * 1 0 0 Execute-only page.
+ * 1 0 1 Read-execute page.
+ * 1 1 0 Reserved for future use.
+ * 1 1 1 Read-write-execute page.
+ */
+static inline bool pte_is_table(pte_t p)
+{
+ /*
+ * According to the spec if V=1 and W=1 then R also needs to be 1 as
+ * R = 0 is reserved for future use ( look at the Table 4.5 ) so check
+ * in ASSERT that if (V==1 && W==1) then R isn't 0.
+ *
+ * PAGE_HYPERVISOR_RW contains PTE_VALID too.
+ */
+ ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID | PTE_WRITABLE)));
+
+ return ((p.pte & (PTE_VALID | PTE_ACCESS_MASK)) == PTE_VALID);
+}
+
+static inline bool pte_is_mapping(pte_t p)
+{
+ /* See pte_is_table() */
+ ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID | PTE_WRITABLE)));
+
+ return (p.pte & PTE_VALID) && (p.pte & PTE_ACCESS_MASK);
+}
+
static inline void invalidate_icache(void)
{
BUG_ON("unimplemented");
diff --git a/xen/arch/riscv/include/asm/riscv_encoding.h b/xen/arch/riscv/include/asm/riscv_encoding.h
index 58abe5eccc..e31e94e77e 100644
--- a/xen/arch/riscv/include/asm/riscv_encoding.h
+++ b/xen/arch/riscv/include/asm/riscv_encoding.h
@@ -164,6 +164,7 @@
#define SSTATUS_SD SSTATUS64_SD
#define SATP_MODE SATP64_MODE
#define SATP_MODE_SHIFT SATP64_MODE_SHIFT
+#define SATP_PPN_MASK SATP64_PPN
#define HGATP_PPN HGATP64_PPN
#define HGATP_VMID_SHIFT HGATP64_VMID_SHIFT
@@ -174,6 +175,7 @@
#define SSTATUS_SD SSTATUS32_SD
#define SATP_MODE SATP32_MODE
#define SATP_MODE_SHIFT SATP32_MODE_SHIFT
+#define SATP_PPN_MASK SATP32_PPN
#define HGATP_PPN HGATP32_PPN
#define HGATP_VMID_SHIFT HGATP32_VMID_SHIFT
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index b8ff91cf4e..e8430def14 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -369,12 +369,3 @@ int destroy_xen_mappings(unsigned long s, unsigned long e)
BUG_ON("unimplemented");
return -1;
}
-
-int map_pages_to_xen(unsigned long virt,
- mfn_t mfn,
- unsigned long nr_mfns,
- unsigned int flags)
-{
- BUG_ON("unimplemented");
- return -1;
-}
diff --git a/xen/arch/riscv/pt.c b/xen/arch/riscv/pt.c
new file mode 100644
index 0000000000..a5552a4871
--- /dev/null
+++ b/xen/arch/riscv/pt.c
@@ -0,0 +1,421 @@
+#include <xen/bug.h>
+#include <xen/domain_page.h>
+#include <xen/errno.h>
+#include <xen/lib.h>
+#include <xen/mm.h>
+#include <xen/pfn.h>
+#include <xen/pmap.h>
+#include <xen/spinlock.h>
+
+#include <asm/flushtlb.h>
+#include <asm/page.h>
+
+static inline mfn_t get_root_page(void)
+{
+ paddr_t root_maddr = pfn_to_paddr(csr_read(CSR_SATP) & SATP_PPN_MASK);
+
+ return maddr_to_mfn(root_maddr);
+}
+
+/*
+ * Sanity check a page table entry about to be updated as per an (MFN,flags)
+ * tuple.
+ * See the comment about the possible combination of (mfn, flags) in
+ * the comment above pt_update().
+ */
+static bool pt_check_entry(pte_t entry, mfn_t mfn, unsigned int flags)
+{
+ /* Sanity check when modifying an entry. */
+ if ( (flags & PTE_VALID) && mfn_eq(mfn, INVALID_MFN) )
+ {
+ /* We don't allow modifying an invalid entry. */
+ if ( !pte_is_valid(entry) )
+ {
+ dprintk(XENLOG_ERR, "Modifying invalid entry is not allowed\n");
+ return false;
+ }
+
+ /* We don't allow modifying a table entry */
+ if ( pte_is_table(entry) )
+ {
+ dprintk(XENLOG_ERR, "Modifying a table entry is not allowed\n");
+ return false;
+ }
+ }
+ /* Sanity check when inserting a mapping */
+ else if ( flags & PTE_VALID )
+ {
+ /*
+ * We don't allow replacing any valid entry.
+ *
+ * Note that the function pt_update() relies on this
+ * assumption and will skip the TLB flush (when Svvptc
+ * extension will be ratified). The function will need
+ * to be updated if the check is relaxed.
+ */
+ if ( pte_is_valid(entry) )
+ {
+ if ( pte_is_mapping(entry) )
+ dprintk(XENLOG_ERR, "Changing MFN for valid PTE is not allowed (%#"PRI_mfn" -> %#"PRI_mfn")\n",
+ mfn_x(mfn_from_pte(entry)), mfn_x(mfn));
+ else
+ dprintk(XENLOG_ERR, "Trying to replace table with mapping\n");
+ return false;
+ }
+ }
+ /* Sanity check when removing a mapping. */
+ else if ( !(flags & PTE_POPULATE) )
+ {
+ /* We should be here with an invalid MFN. */
+ ASSERT(mfn_eq(mfn, INVALID_MFN));
+
+ /* We don't allow removing a table */
+ if ( pte_is_table(entry) )
+ {
+ dprintk(XENLOG_ERR, "Removing a table is not allowed\n");
+ return false;
+ }
+ }
+ /* Sanity check when populating the page-table. No check so far. */
+ else
+ {
+ /* We should be here with an invalid MFN */
+ ASSERT(mfn_eq(mfn, INVALID_MFN));
+ }
+
+ return true;
+}
+
+static pte_t *map_table(mfn_t mfn)
+{
+ /*
+ * During early boot, map_domain_page() may be unusable. Use the
+ * PMAP to map temporarily a page-table.
+ */
+ if ( system_state == SYS_STATE_early_boot )
+ return pmap_map(mfn);
+
+ return map_domain_page(mfn);
+}
+
+static void unmap_table(const pte_t *table)
+{
+ /*
+ * During early boot, map_table() will not use map_domain_page()
+ * but the PMAP.
+ */
+ if ( system_state == SYS_STATE_early_boot )
+ pmap_unmap(table);
+ else
+ unmap_domain_page(table);
+}
+
+static int create_table(pte_t *entry)
+{
+ mfn_t mfn;
+ void *p;
+ pte_t pte;
+
+ if ( system_state != SYS_STATE_early_boot )
+ {
+ struct page_info *pg = alloc_domheap_page(NULL, 0);
+
+ if ( pg == NULL )
+ return -ENOMEM;
+
+ mfn = page_to_mfn(pg);
+ }
+ else
+ mfn = alloc_boot_pages(1, 1);
+
+ p = map_table(mfn);
+ clear_page(p);
+ unmap_table(p);
+
+ pte = pte_from_mfn(mfn, PTE_TABLE);
+ write_pte(entry, pte);
+
+ return 0;
+}
+
+#define XEN_TABLE_MAP_NONE 0
+#define XEN_TABLE_MAP_NOMEM 1
+#define XEN_TABLE_SUPER_PAGE 2
+#define XEN_TABLE_NORMAL 3
+
+/*
+ * Take the currently mapped table, find the corresponding entry,
+ * and map the next table, if available.
+ *
+ * The alloc_tbl parameters indicates whether intermediate tables should
+ * be allocated when not present.
+ *
+ * Return values:
+ * XEN_TABLE_MAP_FAILED: Either alloc_only was set and the entry
+ * was empty, or allocating a new page failed.
+ * XEN_TABLE_NORMAL: next level or leaf mapped normally
+ * XEN_TABLE_SUPER_PAGE: The next entry points to a superpage.
+ */
+static int pt_next_level(bool alloc_tbl, pte_t **table, unsigned int offset)
+{
+ pte_t *entry;
+ mfn_t mfn;
+
+ entry = *table + offset;
+
+ if ( !pte_is_valid(*entry) )
+ {
+ if ( !alloc_tbl )
+ return XEN_TABLE_MAP_NONE;
+
+ if ( create_table(entry) )
+ return XEN_TABLE_MAP_NOMEM;
+ }
+
+ if ( pte_is_mapping(*entry) )
+ return XEN_TABLE_SUPER_PAGE;
+
+ mfn = mfn_from_pte(*entry);
+
+ unmap_table(*table);
+ *table = map_table(mfn);
+
+ return XEN_TABLE_NORMAL;
+}
+
+/* Update an entry at the level @target. */
+static int pt_update_entry(mfn_t root, vaddr_t virt,
+ mfn_t mfn, unsigned int target,
+ unsigned int flags)
+{
+ int rc;
+ unsigned int level = HYP_PT_ROOT_LEVEL;
+ pte_t *table;
+ /*
+ * The intermediate page table shouldn't be allocated when MFN isn't
+ * valid and we are not populating page table.
+ * This means we either modify permissions or remove an entry, or
+ * inserting brand new entry.
+ *
+ * See the comment above pt_update() for an additional explanation about
+ * combinations of (mfn, flags).
+ */
+ bool alloc_tbl = !mfn_eq(mfn, INVALID_MFN) || (flags & PTE_POPULATE);
+ pte_t pte, *entry;
+
+ /* convenience aliases */
+ DECLARE_OFFSETS(offsets, virt);
+
+ table = map_table(root);
+ for ( ; level > target; level-- )
+ {
+ rc = pt_next_level(alloc_tbl, &table, offsets[level]);
+ if ( rc == XEN_TABLE_MAP_NOMEM )
+ {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ if ( rc == XEN_TABLE_MAP_NONE )
+ {
+ rc = 0;
+ goto out;
+ }
+
+ if ( rc != XEN_TABLE_NORMAL )
+ break;
+ }
+
+ if ( level != target )
+ {
+ dprintk(XENLOG_ERR,
+ "%s: Shattering superpage is not supported\n", __func__);
+ rc = -EOPNOTSUPP;
+ goto out;
+ }
+
+ entry = table + offsets[level];
+
+ rc = -EINVAL;
+ if ( !pt_check_entry(*entry, mfn, flags) )
+ goto out;
+
+ /* We are removing the page */
+ if ( !(flags & PTE_VALID) )
+ /*
+ * There is also a check in pt_check_entry() which check that
+ * mfn=INVALID_MFN
+ */
+ pte.pte = 0;
+ else
+ {
+ /* We are inserting a mapping => Create new pte. */
+ if ( !mfn_eq(mfn, INVALID_MFN) )
+ pte = pte_from_mfn(mfn, PTE_VALID);
+ else /* We are updating the permission => Copy the current pte. */
+ {
+ pte = *entry;
+ pte.pte &= ~PTE_ACCESS_MASK;
+ }
+
+ /* update permission according to the flags */
+ pte.pte |= (flags & PTE_ACCESS_MASK) | PTE_ACCESSED | PTE_DIRTY;
+ }
+
+ write_pte(entry, pte);
+
+ rc = 0;
+
+ out:
+ unmap_table(table);
+
+ return rc;
+}
+
+/* Return the level where mapping should be done */
+static int pt_mapping_level(unsigned long vfn, mfn_t mfn, unsigned long nr,
+ unsigned int flags)
+{
+ unsigned int level = 0;
+ unsigned long mask;
+ unsigned int i;
+
+ /*
+ * Use a larger mapping than 4K unless the caller specifically requests
+ * 4K mapping
+ */
+ if ( unlikely(flags & PTE_SMALL) )
+ return level;
+
+ /*
+ * Don't take into account the MFN when removing mapping (i.e
+ * MFN_INVALID) to calculate the correct target order.
+ *
+ * `vfn` and `mfn` must be both superpage aligned.
+ * They are or-ed together and then checked against the size of
+ * each level.
+ *
+ * `left` ( variable declared in pt_update() ) is not included
+ * and checked separately to allow superpage mapping even if it
+ * is not properly aligned (the user may have asked to map 2MB + 4k).
+ */
+ mask = !mfn_eq(mfn, INVALID_MFN) ? mfn_x(mfn) : 0;
+ mask |= vfn;
+
+ for ( i = HYP_PT_ROOT_LEVEL; i != 0; i-- )
+ {
+ if ( !(mask & (BIT(XEN_PT_LEVEL_ORDER(i), UL) - 1)) &&
+ (nr >= BIT(XEN_PT_LEVEL_ORDER(i), UL)) )
+ {
+ level = i;
+ break;
+ }
+ }
+
+ return level;
+}
+
+static DEFINE_SPINLOCK(pt_lock);
+
+/*
+ * If `mfn` equals `INVALID_MFN`, it indicates that the following page table
+ * update operation might be related to either:
+ * - populating the table (PTE_POPULATE will be set additionaly),
+ * - destroying a mapping (PTE_VALID=0),
+ * - modifying an existing mapping (PTE_VALID=1).
+ *
+ * If `mfn` != INVALID_MFN and flags has PTE_VALID bit set then it means that
+ * inserting will be done.
+ */
+static int pt_update(vaddr_t virt, mfn_t mfn,
+ unsigned long nr_mfns, unsigned int flags)
+{
+ int rc = 0;
+ unsigned long vfn = PFN_DOWN(virt);
+ unsigned long left = nr_mfns;
+ const mfn_t root = get_root_page();
+
+ /*
+ * It is bad idea to have mapping both writeable and
+ * executable.
+ * When modifying/creating mapping (i.e PTE_VALID is set),
+ * prevent any update if this happen.
+ */
+ if ( (flags & PTE_VALID) && (flags & PTE_WRITABLE) &&
+ (flags & PTE_EXECUTABLE) )
+ {
+ dprintk(XENLOG_ERR,
+ "Mappings should not be both Writeable and Executable\n");
+ return -EINVAL;
+ }
+
+ if ( !IS_ALIGNED(virt, PAGE_SIZE) )
+ {
+ dprintk(XENLOG_ERR,
+ "The virtual address is not aligned to the page-size\n");
+ return -EINVAL;
+ }
+
+ spin_lock(&pt_lock);
+
+ while ( left )
+ {
+ unsigned int order, level;
+
+ level = pt_mapping_level(vfn, mfn, left, flags);
+ order = XEN_PT_LEVEL_ORDER(level);
+
+ ASSERT(left >= BIT(order, UL));
+
+ rc = pt_update_entry(root, vfn << PAGE_SHIFT, mfn, level, flags);
+ if ( rc )
+ break;
+
+ vfn += 1UL << order;
+ if ( !mfn_eq(mfn, INVALID_MFN) )
+ mfn = mfn_add(mfn, 1UL << order);
+
+ left -= (1UL << order);
+ }
+
+ /* Ensure that PTEs are all updated before flushing */
+ RISCV_FENCE(rw, rw);
+
+ spin_unlock(&pt_lock);
+
+ /*
+ * Always flush TLB at the end of the function as non-present entries
+ * can be put in the TLB.
+ *
+ * The remote fence operation applies to the entire address space if
+ * either:
+ * - start and size are both 0, or
+ * - size is equal to 2^XLEN-1.
+ *
+ * TODO: come up with something which will allow not to flash the entire
+ * address space.
+ */
+ flush_tlb_range_va(0, 0);
+
+ return rc;
+}
+
+int map_pages_to_xen(unsigned long virt,
+ mfn_t mfn,
+ unsigned long nr_mfns,
+ unsigned int flags)
+{
+ /*
+ * Ensure that flags has PTE_VALID bit as map_pages_to_xen() is supposed
+ * to create a mapping.
+ *
+ * Ensure that we have a valid MFN before proceeding.
+ *
+ * If the MFN is invalid, pt_update() might misinterpret the operation,
+ * treating it as either a population, a mapping destruction,
+ * or a mapping modification.
+ */
+ ASSERT(!mfn_eq(mfn, INVALID_MFN) && (flags & PTE_VALID));
+
+ return pt_update(virt, mfn, nr_mfns, flags);
+}
--
2.46.1
On 27.09.2024 18:33, Oleksii Kurochko wrote:
> +static bool pt_check_entry(pte_t entry, mfn_t mfn, unsigned int flags)
> +{
> + /* Sanity check when modifying an entry. */
> + if ( (flags & PTE_VALID) && mfn_eq(mfn, INVALID_MFN) )
> + {
> + /* We don't allow modifying an invalid entry. */
> + if ( !pte_is_valid(entry) )
> + {
> + dprintk(XENLOG_ERR, "Modifying invalid entry is not allowed\n");
> + return false;
> + }
> +
> + /* We don't allow modifying a table entry */
> + if ( pte_is_table(entry) )
> + {
> + dprintk(XENLOG_ERR, "Modifying a table entry is not allowed\n");
> + return false;
> + }
> + }
> + /* Sanity check when inserting a mapping */
> + else if ( flags & PTE_VALID )
> + {
> + /*
> + * We don't allow replacing any valid entry.
> + *
> + * Note that the function pt_update() relies on this
> + * assumption and will skip the TLB flush (when Svvptc
> + * extension will be ratified). The function will need
> + * to be updated if the check is relaxed.
> + */
> + if ( pte_is_valid(entry) )
> + {
> + if ( pte_is_mapping(entry) )
> + dprintk(XENLOG_ERR, "Changing MFN for valid PTE is not allowed (%#"PRI_mfn" -> %#"PRI_mfn")\n",
> + mfn_x(mfn_from_pte(entry)), mfn_x(mfn));
Nit: Indentation is now off by one.
> +#define XEN_TABLE_MAP_NONE 0
> +#define XEN_TABLE_MAP_NOMEM 1
> +#define XEN_TABLE_SUPER_PAGE 2
> +#define XEN_TABLE_NORMAL 3
> +
> +/*
> + * Take the currently mapped table, find the corresponding entry,
> + * and map the next table, if available.
> + *
> + * The alloc_tbl parameters indicates whether intermediate tables should
> + * be allocated when not present.
> + *
> + * Return values:
> + * XEN_TABLE_MAP_FAILED: Either alloc_only was set and the entry
> + * was empty, or allocating a new page failed.
> + * XEN_TABLE_NORMAL: next level or leaf mapped normally
> + * XEN_TABLE_SUPER_PAGE: The next entry points to a superpage.
This part of the comment is now stale.
> + */
> +static int pt_next_level(bool alloc_tbl, pte_t **table, unsigned int offset)
> +{
> + pte_t *entry;
> + mfn_t mfn;
> +
> + entry = *table + offset;
> +
> + if ( !pte_is_valid(*entry) )
> + {
> + if ( !alloc_tbl )
> + return XEN_TABLE_MAP_NONE;
> +
> + if ( create_table(entry) )
> + return XEN_TABLE_MAP_NOMEM;
At the risk of being overly picky: You still lose -ENOMEM here. I'd suggest
to make create_table() return boolean (success / fail) to eliminate that
concern. Any hypothetical plan for someone to add another error code there
will then hit the return type aspect, pointing out that call sites need
looking at for such a change to be correct.
Jan
On Mon, 2024-09-30 at 17:30 +0200, Jan Beulich wrote:
> > + */
> > +static int pt_next_level(bool alloc_tbl, pte_t **table, unsigned
> > int offset)
> > +{
> > + pte_t *entry;
> > + mfn_t mfn;
> > +
> > + entry = *table + offset;
> > +
> > + if ( !pte_is_valid(*entry) )
> > + {
> > + if ( !alloc_tbl )
> > + return XEN_TABLE_MAP_NONE;
> > +
> > + if ( create_table(entry) )
> > + return XEN_TABLE_MAP_NOMEM;
>
> At the risk of being overly picky: You still lose -ENOMEM here. I'd
> suggest
> to make create_table() return boolean (success / fail) to eliminate
> that
> concern. Any hypothetical plan for someone to add another error code
> there
> will then hit the return type aspect, pointing out that call sites
> need
> looking at for such a change to be correct.
I agree with these changes. Let's go with this approach.
Thanks.
~ Oleksii
Missed to add revision log:
---
Changes in V8:
- drop PTE_LEAF_MASK.
- update the comment above pte_is_table(): drop table number and use
just "the encoding of the permission bits".
- declare pte_is_table() as static.
- drop const from the argument of pte_is_table
- drop the "const" comment before the argument of pte_is_mapping().
- update the comment above ASSERT() in pte_is_mapping() to : See
pte_is_table().
- drop "const" from the return type of get_root_page().
- update the comment above "pt_check_entry()".
- start the comment with capital letter.
- update the way how PTE_ACCESS_MASK bits are cleared before being
updated by
the value in flags.
- use dprintk() instead of printk() in riscv/pt.c
- introduce XEN_TABLE_MAP_NONE and XEN_TABLE_MAP_NOMEM instead of
XEN_TABLE_MAP_FAILED
and correspondingly update part of the code of pt_next_level()'s
return value
handling in pt_update_entry.
- update type of virt to vaddr_t for pt_update_entry()
---
Changes in V7:
- rename PTE_XWV_BITS to PTE_LEAF_MASK.
- drop PTE_XWV_MASK, PTE_RWX_MASK.
- introduce PTE_ACCESS_MASK.
- update the ASSERT and the comment about it in pte_is_mapping().
- add the same ASSERT as in pte_is_mapping() to pte_is_table().
- update the comment above pte_is_table().
- use PTE_ACCESS_MASK inside pte_is_{table,mapping} instead of
encoding
access bit explicitly.
- define SATP_PPN_MASK using SATP{32,64}_PPN.
- drop inclusion of #include <xen/mm-frame.h> in riscv/pt.c as
xen/mm.h is
included.
- use pfn_to_paddr() in get_root_page() instead of open-coding of
pfn_to_paddr().
- update if the comment and the if (...) in pt_update_entry() above
the check
in case of pt_next_level() returns XEN_TABLE_MAP_FAILED.
- update the the comment above pt_update(): drop unecessary mentioning
of INVALID_MFN
and blanks inside parentheses.
- drop "full stops" in printk().
- correct the condition in ASSERT() in map_pages_to_xen().
- clear permission bits before updating the permissions in
pt_update_entry().
---
Changes in V6:
- update the commit message.
- correct the comment above flush_tlb_range_va().
- add PTE_READABLE to the check of pte.rwx permissions in
pte_is_mapping().
- s/printk/dprintk in pt_check_entry().
- drop unnecessary ASSERTS() in pt_check_entry().
- drop checking of PTE_VALID flags in /* Sanity check when removing
a mapping */ because of the earlier check.
- drop ASSERT(flags & PTE_POPULATE) in /* Sanity check when populating
the page-table */
section as in the earlier if it is checked.
- pt_next_level() changes:
- invert if ( alloc_tbl ) condition.
- drop local variable ret.
- pt_update_entry() changes:
- invert definition of alloc_tbl.
- update the comment inside "if ( rc == XEN_TABLE_MAP_FAILED )".
- drop else for mentioned above if (...).
- clear some PTE flags before update.
- s/xen_pt_lock/pt_lock
- use PFN_DOWN() for vfn variable definition in pt_update().
- drop definition of PTE_{R,W,X}_MASK.
- introduce PTE_XWV_BITS and PTE_XWV_MASK() for convenience and use
them in if (...)
in pt_update().
- update the comment above pt_update().
- change memset(&pte, 0x00, sizeof(pte)) to pte.pte = 0.
- add the comment above pte_is_table().
- add ASSERT in pte_is_mapping() to check the cases which are reserved
for future
use.
---
Changes in V5:
- s/xen_{un}map/{un}map
- introduce PTE_SMALL instead of PTE_BLOCK.
- update the comment above defintion of PTE_4K_PAGES.
- code style fixes.
- s/RV_STAGE1_MODE > SATP_MODE_SV48/RV_STAGE1_MODE > SATP_MODE_SV39
around
DECLARE_OFFSETS macros.
- change type of root_maddr from unsgined long to maddr_t.
- drop duplicated check ( if (rc) break ) in pt_update() inside while
cycle.
- s/1U/1UL
- put 'spin_unlock(&xen_pt_lock);' ahead of TLB flush in pt_update().
- update the commit message.
- update the comment above ASSERT() in map_pages_to_xen() and also
update
the check within ASSERT() to check that flags has PTE_VALID bit set.
- update the comment above pt_update() function.
- add the comment inside pt_check_entry().
- update the TLB flushing region in pt_update().
- s/alloc_only/alloc_tbl
---
Changes in V4:
- update the commit message.
- drop xen_ prefix for functions: xen_pt_update(),
xen_pt_mapping_level(),
xen_pt_update_entry(), xen_pt_next_level(), xen_pt_check_entry().
- drop 'select GENERIC_PT' for CONFIG_RISCV. There is no GENERIC_PT
anymore.
- update implementation of flush_xen_tlb_range_va and
s/flush_xen_tlb_range_va/flush_tlb_range_va
- s/pte_get_mfn/mfn_from_pte. Others similar definitions I decided not
to touch as
they were introduced before and this patter of naming such type of
macros will be applied
for newly introduced macros.
- drop _PAGE_* definitions and use analogues of PTE_*.
- introduce PTE_{W,X,R}_MASK and drop PAGE_{XN,W,X}_MASK. Also drop
_PAGE_{*}_BIT
- introduce PAGE_HYPERVISOR_RX.
- drop unused now l3_table_offset.
- drop struct pt_t as it was used only for one function. If it will be
needed in the future
pt_t will be re-introduced.
- code styles fixes in pte_is_table(). drop level argument from t.
- update implementation and prototype of pte_is_mapping().
- drop level argument from pt_next_level().
- introduce definition of SATP_PPN_MASK.
- isolate PPN of CSR_SATP before shift by PAGE_SHIFT.
- drop set_permission() functions as it is not used more then once.
- update prototype of pt_check_entry(): drop level argument as it is
not used.
- pt_check_entry():
- code style fixes
- update the sanity check when modifying an entry
- update the sanity check when when removing a mapping.
- s/read_only/alloc_only.
- code style fixes for pt_next_level().
- pt_update_entry() changes:
- drop arch_level variable inisde pt_update_entry()
- drop convertion near virt to paddr_t in DECLARE_OFFSETS(offsets,
virt);
- pull out "goto out inside first 'for' cycle.
- drop braces for 'if' cases which has only one line.
- ident 'out' label with one blank.
- update the comment above alloc_only and also definition to take
into
account that if pte population was requested or not.
- drop target variable and rename arch_target argument of the
function to
target.
- pt_mapping_level() changes:
- move the check if PTE_BLOCK should be mapped on the top of the
function.
- change int i to unsigned int and update 'for' cycle
correspondingly.
- update prototye of pt_update():
- drop the comment above nr_mfns and drop const to be consistent
with other
arguments.
- always flush TLB at the end of the function as non-present entries
can be put
in the TLB.
- add fence before TLB flush to ensure that PTEs are all updated
before flushing.
- s/XEN_TABLE_NORMAL_PAGE/XEN_TABLE_NORMAL
- add a check in map_pages_to_xen() the mfn is not INVALID_MFN.
- add the comment on top of pt_update() how mfn = INVALID_MFN is
considered.
- s/_PAGE_BLOCK/PTE_BLOCK.
- add the comment with additional explanation for PTE_BLOCK.
- drop defintion of FIRST_SIZE as it isn't used.
---
Changes in V3:
- new patch. ( Technically it is reworked version of the generic
approach
which I tried to suggest in the previous version )
---
~ Oleksii
On Fri, 2024-09-27 at 18:33 +0200, Oleksii Kurochko wrote:
> Implement map_pages_to_xen() which requires several
> functions to manage page tables and entries:
> - pt_update()
> - pt_mapping_level()
> - pt_update_entry()
> - pt_next_level()
> - pt_check_entry()
>
> To support these operations, add functions for creating,
> mapping, and unmapping Xen tables:
> - create_table()
> - map_table()
> - unmap_table()
>
> Introduce PTE_SMALL to indicate that 4KB mapping is needed
> and PTE_POPULATE.
>
> In addition introduce flush_tlb_range_va() for TLB flushing across
> CPUs after updating the PTE for the requested mapping.
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> ---
> xen/arch/riscv/Makefile | 1 +
> xen/arch/riscv/include/asm/flushtlb.h | 9 +
> xen/arch/riscv/include/asm/mm.h | 2 +
> xen/arch/riscv/include/asm/page.h | 80 ++++
> xen/arch/riscv/include/asm/riscv_encoding.h | 2 +
> xen/arch/riscv/mm.c | 9 -
> xen/arch/riscv/pt.c | 421
> ++++++++++++++++++++
> 7 files changed, 515 insertions(+), 9 deletions(-)
> create mode 100644 xen/arch/riscv/pt.c
>
> diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
> index 6832549133..a5eb2aed4b 100644
> --- a/xen/arch/riscv/Makefile
> +++ b/xen/arch/riscv/Makefile
> @@ -1,6 +1,7 @@
> obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> obj-y += entry.o
> obj-y += mm.o
> +obj-y += pt.o
> obj-$(CONFIG_RISCV_64) += riscv64/
> obj-y += sbi.o
> obj-y += setup.o
> diff --git a/xen/arch/riscv/include/asm/flushtlb.h
> b/xen/arch/riscv/include/asm/flushtlb.h
> index f4a735fd6c..43214f5e95 100644
> --- a/xen/arch/riscv/include/asm/flushtlb.h
> +++ b/xen/arch/riscv/include/asm/flushtlb.h
> @@ -5,12 +5,21 @@
> #include <xen/bug.h>
> #include <xen/cpumask.h>
>
> +#include <asm/sbi.h>
> +
> /* Flush TLB of local processor for address va. */
> static inline void flush_tlb_one_local(vaddr_t va)
> {
> asm volatile ( "sfence.vma %0" :: "r" (va) : "memory" );
> }
>
> +/* Flush a range of VA's hypervisor mappings from the TLB of all
> processors. */
> +static inline void flush_tlb_range_va(vaddr_t va, size_t size)
> +{
> + BUG_ON(!sbi_has_rfence());
> + sbi_remote_sfence_vma(NULL, va, size);
> +}
> +
> /*
> * Filter the given set of CPUs, removing those that definitely
> flushed their
> * TLB since @page_timestamp.
> diff --git a/xen/arch/riscv/include/asm/mm.h
> b/xen/arch/riscv/include/asm/mm.h
> index a0bdc2bc3a..ce1557bb27 100644
> --- a/xen/arch/riscv/include/asm/mm.h
> +++ b/xen/arch/riscv/include/asm/mm.h
> @@ -42,6 +42,8 @@ static inline void *maddr_to_virt(paddr_t ma)
> #define virt_to_mfn(va) __virt_to_mfn(va)
> #define mfn_to_virt(mfn) __mfn_to_virt(mfn)
>
> +#define mfn_from_pte(pte) maddr_to_mfn(pte_to_paddr(pte))
> +
> struct page_info
> {
> /* Each frame can be threaded onto a doubly-linked list. */
> diff --git a/xen/arch/riscv/include/asm/page.h
> b/xen/arch/riscv/include/asm/page.h
> index eb79cb9409..89fa290697 100644
> --- a/xen/arch/riscv/include/asm/page.h
> +++ b/xen/arch/riscv/include/asm/page.h
> @@ -21,6 +21,11 @@
> #define XEN_PT_LEVEL_MAP_MASK(lvl) (~(XEN_PT_LEVEL_SIZE(lvl) - 1))
> #define XEN_PT_LEVEL_MASK(lvl) (VPN_MASK <<
> XEN_PT_LEVEL_SHIFT(lvl))
>
> +/*
> + * PTE format:
> + * | XLEN-1 10 | 9 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
> + * PFN reserved for SW D A G U X W R V
> + */
> #define PTE_VALID BIT(0, UL)
> #define PTE_READABLE BIT(1, UL)
> #define PTE_WRITABLE BIT(2, UL)
> @@ -34,15 +39,49 @@
> #define PTE_LEAF_DEFAULT (PTE_VALID | PTE_READABLE |
> PTE_WRITABLE)
> #define PTE_TABLE (PTE_VALID)
>
> +#define PAGE_HYPERVISOR_RO (PTE_VALID | PTE_READABLE)
> #define PAGE_HYPERVISOR_RW (PTE_VALID | PTE_READABLE |
> PTE_WRITABLE)
> +#define PAGE_HYPERVISOR_RX (PTE_VALID | PTE_READABLE |
> PTE_EXECUTABLE)
>
> #define PAGE_HYPERVISOR PAGE_HYPERVISOR_RW
>
> +/*
> + * The PTE format does not contain the following bits within itself;
> + * they are created artificially to inform the Xen page table
> + * handling algorithm. These bits should not be explicitly written
> + * to the PTE entry.
> + */
> +#define PTE_SMALL BIT(10, UL)
> +#define PTE_POPULATE BIT(11, UL)
> +
> +#define PTE_ACCESS_MASK (PTE_READABLE | PTE_WRITABLE |
> PTE_EXECUTABLE)
> +
> /* Calculate the offsets into the pagetables for a given VA */
> #define pt_linear_offset(lvl, va) ((va) >>
> XEN_PT_LEVEL_SHIFT(lvl))
>
> #define pt_index(lvl, va) (pt_linear_offset((lvl), (va)) & VPN_MASK)
>
> +#define PAGETABLE_ORDER_MASK ((_AC(1, U) << PAGETABLE_ORDER) - 1)
> +#define TABLE_OFFSET(offs) (_AT(unsigned int, offs) &
> PAGETABLE_ORDER_MASK)
> +
> +#if RV_STAGE1_MODE > SATP_MODE_SV39
> +#error "need to to update DECLARE_OFFSETS macros"
> +#else
> +
> +#define l0_table_offset(va) TABLE_OFFSET(pt_linear_offset(0, va))
> +#define l1_table_offset(va) TABLE_OFFSET(pt_linear_offset(1, va))
> +#define l2_table_offset(va) TABLE_OFFSET(pt_linear_offset(2, va))
> +
> +/* Generate an array @var containing the offset for each level from
> @addr */
> +#define DECLARE_OFFSETS(var, addr) \
> + const unsigned int var[] = { \
> + l0_table_offset(addr), \
> + l1_table_offset(addr), \
> + l2_table_offset(addr), \
> + }
> +
> +#endif
> +
> /* Page Table entry */
> typedef struct {
> #ifdef CONFIG_RISCV_64
> @@ -68,6 +107,47 @@ static inline bool pte_is_valid(pte_t p)
> return p.pte & PTE_VALID;
> }
>
> +/*
> + * From the RISC-V spec:
> + * The V bit indicates whether the PTE is valid; if it is 0, all
> other bits
> + * in the PTE are don’t-cares and may be used freely by software.
> + *
> + * If V=1 the encoding of PTE R/W/X bits could be find in "the
> encoding
> + * of the permission bits" table.
> + *
> + * The encoding of the permission bits table:
> + * X W R Meaning
> + * 0 0 0 Pointer to next level of page table.
> + * 0 0 1 Read-only page.
> + * 0 1 0 Reserved for future use.
> + * 0 1 1 Read-write page.
> + * 1 0 0 Execute-only page.
> + * 1 0 1 Read-execute page.
> + * 1 1 0 Reserved for future use.
> + * 1 1 1 Read-write-execute page.
> + */
> +static inline bool pte_is_table(pte_t p)
> +{
> + /*
> + * According to the spec if V=1 and W=1 then R also needs to be
> 1 as
> + * R = 0 is reserved for future use ( look at the Table 4.5 ) so
> check
> + * in ASSERT that if (V==1 && W==1) then R isn't 0.
> + *
> + * PAGE_HYPERVISOR_RW contains PTE_VALID too.
> + */
> + ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID |
> PTE_WRITABLE)));
> +
> + return ((p.pte & (PTE_VALID | PTE_ACCESS_MASK)) == PTE_VALID);
> +}
> +
> +static inline bool pte_is_mapping(pte_t p)
> +{
> + /* See pte_is_table() */
> + ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID |
> PTE_WRITABLE)));
> +
> + return (p.pte & PTE_VALID) && (p.pte & PTE_ACCESS_MASK);
> +}
> +
> static inline void invalidate_icache(void)
> {
> BUG_ON("unimplemented");
> diff --git a/xen/arch/riscv/include/asm/riscv_encoding.h
> b/xen/arch/riscv/include/asm/riscv_encoding.h
> index 58abe5eccc..e31e94e77e 100644
> --- a/xen/arch/riscv/include/asm/riscv_encoding.h
> +++ b/xen/arch/riscv/include/asm/riscv_encoding.h
> @@ -164,6 +164,7 @@
> #define SSTATUS_SD SSTATUS64_SD
> #define SATP_MODE SATP64_MODE
> #define SATP_MODE_SHIFT SATP64_MODE_SHIFT
> +#define SATP_PPN_MASK SATP64_PPN
>
> #define HGATP_PPN HGATP64_PPN
> #define HGATP_VMID_SHIFT HGATP64_VMID_SHIFT
> @@ -174,6 +175,7 @@
> #define SSTATUS_SD SSTATUS32_SD
> #define SATP_MODE SATP32_MODE
> #define SATP_MODE_SHIFT SATP32_MODE_SHIFT
> +#define SATP_PPN_MASK SATP32_PPN
>
> #define HGATP_PPN HGATP32_PPN
> #define HGATP_VMID_SHIFT HGATP32_VMID_SHIFT
> diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
> index b8ff91cf4e..e8430def14 100644
> --- a/xen/arch/riscv/mm.c
> +++ b/xen/arch/riscv/mm.c
> @@ -369,12 +369,3 @@ int destroy_xen_mappings(unsigned long s,
> unsigned long e)
> BUG_ON("unimplemented");
> return -1;
> }
> -
> -int map_pages_to_xen(unsigned long virt,
> - mfn_t mfn,
> - unsigned long nr_mfns,
> - unsigned int flags)
> -{
> - BUG_ON("unimplemented");
> - return -1;
> -}
> diff --git a/xen/arch/riscv/pt.c b/xen/arch/riscv/pt.c
> new file mode 100644
> index 0000000000..a5552a4871
> --- /dev/null
> +++ b/xen/arch/riscv/pt.c
> @@ -0,0 +1,421 @@
> +#include <xen/bug.h>
> +#include <xen/domain_page.h>
> +#include <xen/errno.h>
> +#include <xen/lib.h>
> +#include <xen/mm.h>
> +#include <xen/pfn.h>
> +#include <xen/pmap.h>
> +#include <xen/spinlock.h>
> +
> +#include <asm/flushtlb.h>
> +#include <asm/page.h>
> +
> +static inline mfn_t get_root_page(void)
> +{
> + paddr_t root_maddr = pfn_to_paddr(csr_read(CSR_SATP) &
> SATP_PPN_MASK);
> +
> + return maddr_to_mfn(root_maddr);
> +}
> +
> +/*
> + * Sanity check a page table entry about to be updated as per an
> (MFN,flags)
> + * tuple.
> + * See the comment about the possible combination of (mfn, flags) in
> + * the comment above pt_update().
> + */
> +static bool pt_check_entry(pte_t entry, mfn_t mfn, unsigned int
> flags)
> +{
> + /* Sanity check when modifying an entry. */
> + if ( (flags & PTE_VALID) && mfn_eq(mfn, INVALID_MFN) )
> + {
> + /* We don't allow modifying an invalid entry. */
> + if ( !pte_is_valid(entry) )
> + {
> + dprintk(XENLOG_ERR, "Modifying invalid entry is not
> allowed\n");
> + return false;
> + }
> +
> + /* We don't allow modifying a table entry */
> + if ( pte_is_table(entry) )
> + {
> + dprintk(XENLOG_ERR, "Modifying a table entry is not
> allowed\n");
> + return false;
> + }
> + }
> + /* Sanity check when inserting a mapping */
> + else if ( flags & PTE_VALID )
> + {
> + /*
> + * We don't allow replacing any valid entry.
> + *
> + * Note that the function pt_update() relies on this
> + * assumption and will skip the TLB flush (when Svvptc
> + * extension will be ratified). The function will need
> + * to be updated if the check is relaxed.
> + */
> + if ( pte_is_valid(entry) )
> + {
> + if ( pte_is_mapping(entry) )
> + dprintk(XENLOG_ERR, "Changing MFN for valid PTE is
> not allowed (%#"PRI_mfn" -> %#"PRI_mfn")\n",
> + mfn_x(mfn_from_pte(entry)), mfn_x(mfn));
> + else
> + dprintk(XENLOG_ERR, "Trying to replace table with
> mapping\n");
> + return false;
> + }
> + }
> + /* Sanity check when removing a mapping. */
> + else if ( !(flags & PTE_POPULATE) )
> + {
> + /* We should be here with an invalid MFN. */
> + ASSERT(mfn_eq(mfn, INVALID_MFN));
> +
> + /* We don't allow removing a table */
> + if ( pte_is_table(entry) )
> + {
> + dprintk(XENLOG_ERR, "Removing a table is not
> allowed\n");
> + return false;
> + }
> + }
> + /* Sanity check when populating the page-table. No check so far.
> */
> + else
> + {
> + /* We should be here with an invalid MFN */
> + ASSERT(mfn_eq(mfn, INVALID_MFN));
> + }
> +
> + return true;
> +}
> +
> +static pte_t *map_table(mfn_t mfn)
> +{
> + /*
> + * During early boot, map_domain_page() may be unusable. Use the
> + * PMAP to map temporarily a page-table.
> + */
> + if ( system_state == SYS_STATE_early_boot )
> + return pmap_map(mfn);
> +
> + return map_domain_page(mfn);
> +}
> +
> +static void unmap_table(const pte_t *table)
> +{
> + /*
> + * During early boot, map_table() will not use map_domain_page()
> + * but the PMAP.
> + */
> + if ( system_state == SYS_STATE_early_boot )
> + pmap_unmap(table);
> + else
> + unmap_domain_page(table);
> +}
> +
> +static int create_table(pte_t *entry)
> +{
> + mfn_t mfn;
> + void *p;
> + pte_t pte;
> +
> + if ( system_state != SYS_STATE_early_boot )
> + {
> + struct page_info *pg = alloc_domheap_page(NULL, 0);
> +
> + if ( pg == NULL )
> + return -ENOMEM;
> +
> + mfn = page_to_mfn(pg);
> + }
> + else
> + mfn = alloc_boot_pages(1, 1);
> +
> + p = map_table(mfn);
> + clear_page(p);
> + unmap_table(p);
> +
> + pte = pte_from_mfn(mfn, PTE_TABLE);
> + write_pte(entry, pte);
> +
> + return 0;
> +}
> +
> +#define XEN_TABLE_MAP_NONE 0
> +#define XEN_TABLE_MAP_NOMEM 1
> +#define XEN_TABLE_SUPER_PAGE 2
> +#define XEN_TABLE_NORMAL 3
> +
> +/*
> + * Take the currently mapped table, find the corresponding entry,
> + * and map the next table, if available.
> + *
> + * The alloc_tbl parameters indicates whether intermediate tables
> should
> + * be allocated when not present.
> + *
> + * Return values:
> + * XEN_TABLE_MAP_FAILED: Either alloc_only was set and the entry
> + * was empty, or allocating a new page failed.
> + * XEN_TABLE_NORMAL: next level or leaf mapped normally
> + * XEN_TABLE_SUPER_PAGE: The next entry points to a superpage.
> + */
> +static int pt_next_level(bool alloc_tbl, pte_t **table, unsigned int
> offset)
> +{
> + pte_t *entry;
> + mfn_t mfn;
> +
> + entry = *table + offset;
> +
> + if ( !pte_is_valid(*entry) )
> + {
> + if ( !alloc_tbl )
> + return XEN_TABLE_MAP_NONE;
> +
> + if ( create_table(entry) )
> + return XEN_TABLE_MAP_NOMEM;
> + }
> +
> + if ( pte_is_mapping(*entry) )
> + return XEN_TABLE_SUPER_PAGE;
> +
> + mfn = mfn_from_pte(*entry);
> +
> + unmap_table(*table);
> + *table = map_table(mfn);
> +
> + return XEN_TABLE_NORMAL;
> +}
> +
> +/* Update an entry at the level @target. */
> +static int pt_update_entry(mfn_t root, vaddr_t virt,
> + mfn_t mfn, unsigned int target,
> + unsigned int flags)
> +{
> + int rc;
> + unsigned int level = HYP_PT_ROOT_LEVEL;
> + pte_t *table;
> + /*
> + * The intermediate page table shouldn't be allocated when MFN
> isn't
> + * valid and we are not populating page table.
> + * This means we either modify permissions or remove an entry,
> or
> + * inserting brand new entry.
> + *
> + * See the comment above pt_update() for an additional
> explanation about
> + * combinations of (mfn, flags).
> + */
> + bool alloc_tbl = !mfn_eq(mfn, INVALID_MFN) || (flags &
> PTE_POPULATE);
> + pte_t pte, *entry;
> +
> + /* convenience aliases */
> + DECLARE_OFFSETS(offsets, virt);
> +
> + table = map_table(root);
> + for ( ; level > target; level-- )
> + {
> + rc = pt_next_level(alloc_tbl, &table, offsets[level]);
> + if ( rc == XEN_TABLE_MAP_NOMEM )
> + {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + if ( rc == XEN_TABLE_MAP_NONE )
> + {
> + rc = 0;
> + goto out;
> + }
> +
> + if ( rc != XEN_TABLE_NORMAL )
> + break;
> + }
> +
> + if ( level != target )
> + {
> + dprintk(XENLOG_ERR,
> + "%s: Shattering superpage is not supported\n",
> __func__);
> + rc = -EOPNOTSUPP;
> + goto out;
> + }
> +
> + entry = table + offsets[level];
> +
> + rc = -EINVAL;
> + if ( !pt_check_entry(*entry, mfn, flags) )
> + goto out;
> +
> + /* We are removing the page */
> + if ( !(flags & PTE_VALID) )
> + /*
> + * There is also a check in pt_check_entry() which check
> that
> + * mfn=INVALID_MFN
> + */
> + pte.pte = 0;
> + else
> + {
> + /* We are inserting a mapping => Create new pte. */
> + if ( !mfn_eq(mfn, INVALID_MFN) )
> + pte = pte_from_mfn(mfn, PTE_VALID);
> + else /* We are updating the permission => Copy the current
> pte. */
> + {
> + pte = *entry;
> + pte.pte &= ~PTE_ACCESS_MASK;
> + }
> +
> + /* update permission according to the flags */
> + pte.pte |= (flags & PTE_ACCESS_MASK) | PTE_ACCESSED |
> PTE_DIRTY;
> + }
> +
> + write_pte(entry, pte);
> +
> + rc = 0;
> +
> + out:
> + unmap_table(table);
> +
> + return rc;
> +}
> +
> +/* Return the level where mapping should be done */
> +static int pt_mapping_level(unsigned long vfn, mfn_t mfn, unsigned
> long nr,
> + unsigned int flags)
> +{
> + unsigned int level = 0;
> + unsigned long mask;
> + unsigned int i;
> +
> + /*
> + * Use a larger mapping than 4K unless the caller specifically
> requests
> + * 4K mapping
> + */
> + if ( unlikely(flags & PTE_SMALL) )
> + return level;
> +
> + /*
> + * Don't take into account the MFN when removing mapping (i.e
> + * MFN_INVALID) to calculate the correct target order.
> + *
> + * `vfn` and `mfn` must be both superpage aligned.
> + * They are or-ed together and then checked against the size of
> + * each level.
> + *
> + * `left` ( variable declared in pt_update() ) is not included
> + * and checked separately to allow superpage mapping even if it
> + * is not properly aligned (the user may have asked to map 2MB +
> 4k).
> + */
> + mask = !mfn_eq(mfn, INVALID_MFN) ? mfn_x(mfn) : 0;
> + mask |= vfn;
> +
> + for ( i = HYP_PT_ROOT_LEVEL; i != 0; i-- )
> + {
> + if ( !(mask & (BIT(XEN_PT_LEVEL_ORDER(i), UL) - 1)) &&
> + (nr >= BIT(XEN_PT_LEVEL_ORDER(i), UL)) )
> + {
> + level = i;
> + break;
> + }
> + }
> +
> + return level;
> +}
> +
> +static DEFINE_SPINLOCK(pt_lock);
> +
> +/*
> + * If `mfn` equals `INVALID_MFN`, it indicates that the following
> page table
> + * update operation might be related to either:
> + * - populating the table (PTE_POPULATE will be set additionaly),
> + * - destroying a mapping (PTE_VALID=0),
> + * - modifying an existing mapping (PTE_VALID=1).
> + *
> + * If `mfn` != INVALID_MFN and flags has PTE_VALID bit set then it
> means that
> + * inserting will be done.
> + */
> +static int pt_update(vaddr_t virt, mfn_t mfn,
> + unsigned long nr_mfns, unsigned int flags)
> +{
> + int rc = 0;
> + unsigned long vfn = PFN_DOWN(virt);
> + unsigned long left = nr_mfns;
> + const mfn_t root = get_root_page();
> +
> + /*
> + * It is bad idea to have mapping both writeable and
> + * executable.
> + * When modifying/creating mapping (i.e PTE_VALID is set),
> + * prevent any update if this happen.
> + */
> + if ( (flags & PTE_VALID) && (flags & PTE_WRITABLE) &&
> + (flags & PTE_EXECUTABLE) )
> + {
> + dprintk(XENLOG_ERR,
> + "Mappings should not be both Writeable and
> Executable\n");
> + return -EINVAL;
> + }
> +
> + if ( !IS_ALIGNED(virt, PAGE_SIZE) )
> + {
> + dprintk(XENLOG_ERR,
> + "The virtual address is not aligned to the page-
> size\n");
> + return -EINVAL;
> + }
> +
> + spin_lock(&pt_lock);
> +
> + while ( left )
> + {
> + unsigned int order, level;
> +
> + level = pt_mapping_level(vfn, mfn, left, flags);
> + order = XEN_PT_LEVEL_ORDER(level);
> +
> + ASSERT(left >= BIT(order, UL));
> +
> + rc = pt_update_entry(root, vfn << PAGE_SHIFT, mfn, level,
> flags);
> + if ( rc )
> + break;
> +
> + vfn += 1UL << order;
> + if ( !mfn_eq(mfn, INVALID_MFN) )
> + mfn = mfn_add(mfn, 1UL << order);
> +
> + left -= (1UL << order);
> + }
> +
> + /* Ensure that PTEs are all updated before flushing */
> + RISCV_FENCE(rw, rw);
> +
> + spin_unlock(&pt_lock);
> +
> + /*
> + * Always flush TLB at the end of the function as non-present
> entries
> + * can be put in the TLB.
> + *
> + * The remote fence operation applies to the entire address
> space if
> + * either:
> + * - start and size are both 0, or
> + * - size is equal to 2^XLEN-1.
> + *
> + * TODO: come up with something which will allow not to flash
> the entire
> + * address space.
> + */
> + flush_tlb_range_va(0, 0);
> +
> + return rc;
> +}
> +
> +int map_pages_to_xen(unsigned long virt,
> + mfn_t mfn,
> + unsigned long nr_mfns,
> + unsigned int flags)
> +{
> + /*
> + * Ensure that flags has PTE_VALID bit as map_pages_to_xen() is
> supposed
> + * to create a mapping.
> + *
> + * Ensure that we have a valid MFN before proceeding.
> + *
> + * If the MFN is invalid, pt_update() might misinterpret the
> operation,
> + * treating it as either a population, a mapping destruction,
> + * or a mapping modification.
> + */
> + ASSERT(!mfn_eq(mfn, INVALID_MFN) && (flags & PTE_VALID));
> +
> + return pt_update(virt, mfn, nr_mfns, flags);
> +}
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