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kernel/fork: Initialize mm's PASID

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A new mm doesn't have a PASID yet when it's created. Initialize
the mm's PASID on fork() or for init_mm to INVALID_IOASID (-1).

INIT_PASID (0) is reserved for kernel legacy DMA PASID. It cannot be
allocated to a user process. Initializing the process's PASID to 0 may
cause confusion that's why the process uses the reserved kernel legacy
DMA PASID. Initializing the PASID to INVALID_IOASID (-1) explicitly
tells the process doesn't have a valid PASID yet.

Even though the only user of mm_pasid_init() is in fork.c, define it in
<linux/sched/mm.h> as the first of three mm/pasid life cycle functions
(init/set/drop) to keep these all together.

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220207230254.3342514-5-fenghua.yu@intel.com
This commit is contained in:
Fenghua Yu 2022-02-07 15:02:47 -08:00 committed by Borislav Petkov
parent 7a5fbc9bcb
commit a6cbd44093
3 changed files with 16 additions and 8 deletions
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10
include/linux/sched/mm.h
View file

@ -8,6 +8,7 @@
#include <linux/mm_types.h>
#include <linux/gfp.h>
#include <linux/sync_core.h>
#include <linux/ioasid.h>
/*
* Routines for handling mm_structs
@ -433,4 +434,13 @@ static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
}
#endif
#ifdef CONFIG_IOMMU_SVA
static inline void mm_pasid_init(struct mm_struct *mm)
{
mm->pasid = INVALID_IOASID;
}
#else
static inline void mm_pasid_init(struct mm_struct *mm) {}
#endif
#endif /* _LINUX_SCHED_MM_H */

10
kernel/fork.c
View file

@ -97,6 +97,7 @@
#include <linux/scs.h>
#include <linux/io_uring.h>
#include <linux/bpf.h>
#include <linux/sched/mm.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
@ -1019,13 +1020,6 @@ static void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
#endif
}
static void mm_init_pasid(struct mm_struct *mm)
{
#ifdef CONFIG_IOMMU_SVA
mm->pasid = INIT_PASID;
#endif
}
static void mm_init_uprobes_state(struct mm_struct *mm)
{
#ifdef CONFIG_UPROBES
@ -1054,7 +1048,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm_init_cpumask(mm);
mm_init_aio(mm);
mm_init_owner(mm, p);
mm_init_pasid(mm);
mm_pasid_init(mm);
RCU_INIT_POINTER(mm->exe_file, NULL);
mmu_notifier_subscriptions_init(mm);
init_tlb_flush_pending(mm);

4
mm/init-mm.c
View file

@ -10,6 +10,7 @@
#include <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/ioasid.h>
#include <asm/mmu.h>
#ifndef INIT_MM_CONTEXT
@ -38,6 +39,9 @@ struct mm_struct init_mm = {
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
.user_ns = &init_user_ns,
.cpu_bitmap = CPU_BITS_NONE,
#ifdef CONFIG_IOMMU_SVA
.pasid = INVALID_IOASID,
#endif
INIT_MM_CONTEXT(init_mm)
};