[RFC][PATCH v2 10/21] x86/pti: Function to map per-cpu page-table entry

Alexandre Chartre
2020-11-16T14:48:37Z

Wrap the code used by PTI to map a per-cpu page-table entry into
a new function so that this code can be re-used to map other
per-cpu entries.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
arch/x86/mm/pti.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index ebc8cd2f1cd8..71ca245d7b38 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -428,6 +428,21 @@ static void __init pti_clone_p4d(unsigned long addr)
*user_p4d = *kernel_p4d;
}

+/*
+ * Clone a single percpu page.
+ */
+static void __init pti_clone_percpu_page(void *addr)
+{
+ phys_addr_t pa = per_cpu_ptr_to_phys(addr);
+ pte_t *target_pte;
+
+ target_pte = pti_user_pagetable_walk_pte((unsigned long)addr);
+ if (WARN_ON(!target_pte))
+ return;
+
+ *target_pte = pfn_pte(pa >> PAGE_SHIFT, PAGE_KERNEL);
+}
+
/*
* Clone the CPU_ENTRY_AREA and associated data into the user space visible
* page table.
@@ -448,16 +463,8 @@ static void __init pti_clone_user_shared(void)
* This is done for all possible CPUs during boot to ensure
* that it's propagated to all mms.
*/
+ pti_clone_percpu_page(&per_cpu(cpu_tss_rw, cpu));

- unsigned long va = (unsigned long)&per_cpu(cpu_tss_rw, cpu);
- phys_addr_t pa = per_cpu_ptr_to_phys((void *)va);
- pte_t *target_pte;
-
- target_pte = pti_user_pagetable_walk_pte(va);
- if (WARN_ON(!target_pte))
- return;
-
- *target_pte = pfn_pte(pa >> PAGE_SHIFT, PAGE_KERNEL);
}
}

--
2.18.4