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Message-Id: <20210401225833.566238-8-ira.weiny@intel.com>
Date: Thu, 1 Apr 2021 15:58:30 -0700
From: ira.weiny@...el.com
To: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Ira Weiny <ira.weiny@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: [PATCH V6 07/10] x86/pks: Preserve the PKRS MSR on context switch
From: Ira Weiny <ira.weiny@...el.com>
The PKRS MSR is defined as a per-logical-processor register. This
isolates memory access by logical CPU. Unfortunately, the MSR is not
managed by XSAVE. Therefore, tasks must save/restore the MSR value on
context switch.
Define a saved PKRS value in the task struct, as well as a cached
per-logical-processor MSR value which mirrors the MSR value of the
current CPU. Initialize all tasks with the default MSR value. Then, on
schedule in, call write_pkrs() which automatically avoids the overhead
of the MSR write if possible.
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Co-developed-by: Fenghua Yu <fenghua.yu@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>
---
Changes from V4
From kernel test robot <lkp@...el.com>
Fix i386 build: pks_init_task not found
Move MSR_IA32_PKRS and INIT_PKRS_VALUE to patch 5 where they are
'used'. (Technically nothing is used until the final
test patch but this organization makes review better.)
Fix checkpatch errors
Changes from V3
From Dan Williams
make pks_init_task() and pks_sched_in() macros
To avoid Supervisor PKey '#ifdefery' in process.c and
process_64.c
Split write_pkrs() to an earlier patch to be used in setup_pks()
Move Peter's authorship to that patch.
From Dan Williams
Use ARCH_ENABLE_SUPERVISOR_PKEYS
Remove kernel doc comment from write_pkrs
From Thomas Gleixner
Fix where pks_sched_in() is called from.
Should be called from __switch_to()
NOTE: PKS requires x86_64 so there is no need to
update process_32.c
Make pkrs_cache static
Remove unnecessary pkrs_cache declaration
Clean up formatting
Changes from V2
Adjust for PKS enable being final patch.
Changes from V1
Rebase to latest tip/master
Resolve conflicts with INIT_THREAD changes
Changes since RFC V3
Per Dave Hansen
Update commit message
move saved_pkrs to be in a nicer place
Per Peter Zijlstra
Add Comment from Peter
Clean up white space
Update authorship
---
arch/x86/include/asm/processor.h | 47 +++++++++++++++++++++++++++++++-
arch/x86/kernel/process.c | 3 ++
arch/x86/kernel/process_64.c | 2 ++
3 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index dc6d149bf851..e0ffb9c849c5 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -18,6 +18,7 @@ struct vm86;
#include <asm/cpufeatures.h>
#include <asm/page.h>
#include <asm/pgtable_types.h>
+#include <asm/pkeys_common.h>
#include <asm/percpu.h>
#include <asm/msr.h>
#include <asm/desc_defs.h>
@@ -519,6 +520,12 @@ struct thread_struct {
unsigned long cr2;
unsigned long trap_nr;
unsigned long error_code;
+
+#ifdef CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS
+ /* Saved Protection key register for supervisor mappings */
+ u32 saved_pkrs;
+#endif
+
#ifdef CONFIG_VM86
/* Virtual 86 mode info */
struct vm86 *vm86;
@@ -775,6 +782,37 @@ static inline void spin_lock_prefetch(const void *x)
((struct pt_regs *)__ptr) - 1; \
})
+#ifdef CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS
+
+void write_pkrs(u32 new_pkrs);
+
+/*
+ * Define pks_init_task and pks_sched_in as macros to avoid requiring the
+ * definition of struct task_struct in this header while keeping the supervisor
+ * pkey #ifdefery out of process.c and process_64.c
+ */
+
+/*
+ * New tasks get the most restrictive PKRS value.
+ */
+#define pks_init_task(tsk) \
+ tsk->thread.saved_pkrs = INIT_PKRS_VALUE
+
+/*
+ * PKRS is only temporarily changed during specific code paths. Only a
+ * preemption during these windows away from the default value would
+ * require updating the MSR. write_pkrs() handles this optimization.
+ */
+#define pks_sched_in() \
+ write_pkrs(current->thread.saved_pkrs)
+
+#else /* !CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS */
+
+#define pks_init_task(tsk)
+#define pks_sched_in()
+
+#endif /* CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS */
+
#ifdef CONFIG_X86_32
#define INIT_THREAD { \
.sp0 = TOP_OF_INIT_STACK, \
@@ -784,7 +822,14 @@ static inline void spin_lock_prefetch(const void *x)
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
#else
-#define INIT_THREAD { }
+
+#ifdef CONFIG_ARCH_ENABLE_SUPERVISOR_PKEYS
+#define INIT_THREAD { \
+ .saved_pkrs = INIT_PKRS_VALUE, \
+}
+#else
+#define INIT_THREAD { }
+#endif
extern unsigned long KSTK_ESP(struct task_struct *task);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9c214d7085a4..89f8454a8541 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -43,6 +43,7 @@
#include <asm/io_bitmap.h>
#include <asm/proto.h>
#include <asm/frame.h>
+#include <asm/processor.h>
#include "process.h"
@@ -195,6 +196,8 @@ void flush_thread(void)
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
fpu__clear_all(&tsk->thread.fpu);
+
+ pks_init_task(tsk);
}
void disable_TSC(void)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index d08307df69ad..e590ecac1650 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -632,6 +632,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
/* Load the Intel cache allocation PQR MSR. */
resctrl_sched_in();
+ pks_sched_in();
+
return prev_p;
}
--
2.28.0.rc0.12.gb6a658bd00c9
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