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UPSTREAM: arm64: mte: avoid clearing PSTATE.TCO on entry unless necessary

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On some microarchitectures, clearing PSTATE.TCO is expensive. Clearing
TCO is only necessary if in-kernel MTE is enabled, or if MTE is
enabled in the userspace process in synchronous (or, soon, asymmetric)
mode, because we do not report uaccess faults to userspace in none
or asynchronous modes. Therefore, adjust the kernel entry code to
clear TCO only if necessary.

Because it is now possible to switch to a task in which TCO needs to
be clear from a task in which TCO is set, we also need to do the same
thing on task switch.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/I52d82a580bd0500d420be501af2c35fa8c90729e
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220219012945.894950-2-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Bug: 254721825
(cherry picked from commit 38ddf7dafaeaf3fcdea65b3b4dfb06b4bcd9cc15)
Change-Id: I3796002cf2ee6e66ec6703e26b60d73436d73521
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
This commit is contained in:
Peter Collingbourne
2022-02-18 17:29:45 -08:00
committed by Todd Kjos
parent e9aa144c45
commit 1bda08b8bc
4 changed files with 28 additions and 7 deletions
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3
arch/arm64/kernel/entry-common.c
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@@ -6,6 +6,7 @@
*/
#include <linux/context_tracking.h>
#include <linux/kasan.h>
#include <linux/linkage.h>
#include <linux/lockdep.h>
#include <linux/ptrace.h>
@@ -57,6 +58,7 @@ static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
{
__enter_from_kernel_mode(regs);
mte_check_tfsr_entry();
mte_disable_tco_entry(current);
}
/*
@@ -104,6 +106,7 @@ static __always_inline void __enter_from_user_mode(void)
CT_WARN_ON(ct_state() != CONTEXT_USER);
user_exit_irqoff();
trace_hardirqs_off_finish();
mte_disable_tco_entry(current);
}
static __always_inline void enter_from_user_mode(struct pt_regs *regs)