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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 12/18] xen/riscv: Implement p2m_pte_from_mfn() and support PBMT configuration
This patch adds the initial logic for constructing PTEs from MFNs in the RISC-V
p2m subsystem. It includes:
- Implementation of p2m_pte_from_mfn(): Generates a valid PTE using the
given MFN, p2m_type_t, including permission encoding and PBMT attribute
setup.
- New helper p2m_set_permission(): Encodes access rights (r, w, x) into the
PTE based on both p2m type and access permissions.
- p2m_set_type(): Stores the p2m type in PTE's bits. The storage of types,
which don't fit PTE bits, will be implemented separately later.
- Add detection of Svade extension to properly handle a possible page-fault
if A and D bits aren't set.
PBMT type encoding support:
- Introduces an enum pbmt_type_t to represent the PBMT field values.
- Maps types like p2m_mmio_direct_dev to p2m_mmio_direct_io, others default
to pbmt_pma.
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V4:
- p2m_set_permission() updates:
- Update permissions for p2m_ram_rw case, make it also executable.
- Add pernissions setting for p2m_map_foreign_* types.
- Drop setting peromissions for p2m_ext_storage.
- Only turn off PTE_VALID bit for p2m_invalid, don't touch other bits.
- p2m_pte_from_mfn() updates:
- Update ASSERT(), add a check that mfn isn't INVALID_MFN (1)
explicitly to avoid the case when PADDR_MASK isn't narrow enough to
catch the case (1).
- Drop unnessary check around call of p2m_set_type() as this check
is already included inside p2m_set_type().
- Introduce new p2m type p2m_first_external to detect that passed type
is stored in external storage.
- Add handling of PTE's A and D bits in pm2_set_permission. Also, set
PTE_USER bit. For this cpufeatures.{h and c} were updated to be able
to detect availability of Svade extension.
- Drop grant table related code as it isn't going to be used at the moment.
---
Changes in V3:
- s/p2m_entry_from_mfn/p2m_pte_from_mfn.
- s/pbmt_type_t/pbmt_type.
- s/pbmt_max/pbmt_count.
- s/p2m_type_radix_set/p2m_set_type.
- Rework p2m_set_type() to handle only types which are fited into PTEs bits.
Other types will be covered separately.
Update arguments of p2m_set_type(): there is no any reason for p2m anymore.
- p2m_set_permissions() updates:
- Update the code in p2m_set_permission() for cases p2m_raw_rw and
p2m_mmio_direct_io to set proper type permissions.
- Add cases for p2m_grant_map_rw and p2m_grant_map_ro.
- Use ASSERT_UNEACHABLE() instead of BUG() in switch cases of
p2m_set_permissions.
- Add blank lines non-fall-through case blocks in switch cases.
- Set MFN before permissions are set in p2m_pte_from_mfn().
- Update prototype of p2m_entry_from_mfn().
---
Changes in V2:
- New patch. It was a part of a big patch "xen/riscv: implement p2m mapping
functionality" which was splitted to smaller.
---
xen/arch/riscv/cpufeature.c | 1 +
xen/arch/riscv/include/asm/cpufeature.h | 1 +
xen/arch/riscv/include/asm/page.h | 8 ++
xen/arch/riscv/p2m.c | 97 ++++++++++++++++++++++++-
4 files changed, 103 insertions(+), 4 deletions(-)
diff --git a/xen/arch/riscv/cpufeature.c b/xen/arch/riscv/cpufeature.c
index b846a106a3..02b68aeaa4 100644
--- a/xen/arch/riscv/cpufeature.c
+++ b/xen/arch/riscv/cpufeature.c
@@ -138,6 +138,7 @@ const struct riscv_isa_ext_data __initconst riscv_isa_ext[]
= {
RISCV_ISA_EXT_DATA(zbs),
RISCV_ISA_EXT_DATA(smaia),
RISCV_ISA_EXT_DATA(ssaia),
+ RISCV_ISA_EXT_DATA(svade),
RISCV_ISA_EXT_DATA(svpbmt),
};
diff --git a/xen/arch/riscv/include/asm/cpufeature.h
b/xen/arch/riscv/include/asm/cpufeature.h
index 768b84b769..5f756c76db 100644
--- a/xen/arch/riscv/include/asm/cpufeature.h
+++ b/xen/arch/riscv/include/asm/cpufeature.h
@@ -37,6 +37,7 @@ enum riscv_isa_ext_id {
RISCV_ISA_EXT_zbs,
RISCV_ISA_EXT_smaia,
RISCV_ISA_EXT_ssaia,
+ RISCV_ISA_EXT_svade,
RISCV_ISA_EXT_svpbmt,
RISCV_ISA_EXT_MAX
};
diff --git a/xen/arch/riscv/include/asm/page.h
b/xen/arch/riscv/include/asm/page.h
index cb303af0c0..4fa0556073 100644
--- a/xen/arch/riscv/include/asm/page.h
+++ b/xen/arch/riscv/include/asm/page.h
@@ -74,6 +74,14 @@
#define PTE_SMALL BIT(10, UL)
#define PTE_POPULATE BIT(11, UL)
+enum pbmt_type {
+ pbmt_pma,
+ pbmt_nc,
+ pbmt_io,
+ pbmt_rsvd,
+ pbmt_count,
+};
+
#define PTE_ACCESS_MASK (PTE_READABLE | PTE_WRITABLE | PTE_EXECUTABLE)
#define PTE_PBMT_MASK (PTE_PBMT_NOCACHE | PTE_PBMT_IO)
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index 10acfa0a9c..2d4433360d 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -10,6 +10,7 @@
#include <xen/sched.h>
#include <xen/sections.h>
+#include <asm/cpufeature.h>
#include <asm/csr.h>
#include <asm/flushtlb.h>
#include <asm/paging.h>
@@ -288,6 +289,18 @@ static pte_t *p2m_get_root_pointer(struct p2m_domain *p2m,
gfn_t gfn)
return __map_domain_page(p2m->root + root_table_indx);
}
+static int p2m_set_type(pte_t *pte, p2m_type_t t)
+{
+ int rc = 0;
+
+ if ( t > p2m_first_external )
+ panic("unimplemeted\n");
+ else
+ pte->pte |= MASK_INSR(t, P2M_TYPE_PTE_BITS_MASK);
+
+ return rc;
+}
+
static p2m_type_t p2m_get_type(const pte_t pte)
{
p2m_type_t type = MASK_EXTR(pte.pte, P2M_TYPE_PTE_BITS_MASK);
@@ -318,11 +331,87 @@ static inline void p2m_clean_pte(pte_t *p, bool clean_pte)
p2m_write_pte(p, pte, clean_pte);
}
-static pte_t p2m_pte_from_mfn(mfn_t mfn, p2m_type_t t)
+static void p2m_set_permission(pte_t *e, p2m_type_t t)
{
- panic("%s: hasn't been implemented yet\n", __func__);
+ e->pte &= ~PTE_ACCESS_MASK;
+
+ e->pte |= PTE_USER;
+
+ /*
+ * Two schemes to manage the A and D bits are defined:
+ * • The Svade extension: when a virtual page is accessed and the A bit
+ * is clear, or is written and the D bit is clear, a page-fault
+ * exception is raised.
+ * • When the Svade extension is not implemented, the following scheme
+ * applies.
+ * When a virtual page is accessed and the A bit is clear, the PTE is
+ * updated to set the A bit. When the virtual page is written and the
+ * D bit is clear, the PTE is updated to set the D bit. When G-stage
+ * address translation is in use and is not Bare, the G-stage virtual
+ * pages may be accessed or written by implicit accesses to VS-level
+ * memory management data structures, such as page tables.
+ * Thereby to avoid a page-fault in case of Svade is available, it is
+ * necesssary to set A and D bits.
+ */
+ if ( riscv_isa_extension_available(NULL, RISCV_ISA_EXT_svade) )
+ e->pte |= PTE_ACCESSED | PTE_DIRTY;
+
+ switch ( t )
+ {
+ case p2m_map_foreign_rw:
+ case p2m_mmio_direct_io:
+ e->pte |= PTE_READABLE | PTE_WRITABLE;
+ break;
+
+ case p2m_ram_rw:
+ e->pte |= PTE_ACCESS_MASK;
+ break;
+
+ case p2m_invalid:
+ e->pte &= ~PTE_VALID;
+ break;
+
+ case p2m_map_foreign_ro:
+ e->pte |= PTE_READABLE;
+ break;
+
+ default:
+ ASSERT_UNREACHABLE();
+ break;
+ }
+}
+
+static pte_t p2m_pte_from_mfn(mfn_t mfn, p2m_type_t t, bool is_table)
+{
+ pte_t e = (pte_t) { PTE_VALID };
+
+ switch ( t )
+ {
+ case p2m_mmio_direct_io:
+ e.pte |= PTE_PBMT_IO;
+ break;
+
+ default:
+ break;
+ }
+
+ pte_set_mfn(&e, mfn);
+
+ ASSERT(!(mfn_to_maddr(mfn) & ~PADDR_MASK) || mfn_eq(mfn, INVALID_MFN));
+
+ if ( !is_table )
+ {
+ p2m_set_permission(&e, t);
+ p2m_set_type(&e, t);
+ }
+ else
+ /*
+ * According to the spec and table "Encoding of PTE R/W/X fields":
+ * X=W=R=0 -> Pointer to next level of page table.
+ */
+ e.pte &= ~PTE_ACCESS_MASK;
- return (pte_t) { .pte = 0 };
+ return e;
}
#define P2M_TABLE_MAP_NONE 0
@@ -580,7 +669,7 @@ static int p2m_set_entry(struct p2m_domain *p2m,
p2m_clean_pte(entry, p2m->clean_dcache);
else
{
- pte_t pte = p2m_pte_from_mfn(mfn, t);
+ pte_t pte = p2m_pte_from_mfn(mfn, t, false);
p2m_write_pte(entry, pte, p2m->clean_dcache);
--
2.51.0
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