From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, "H . J . Lu" <hjl.tools@gmail.com>,
Andi Kleen <ak@linux.intel.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [RFC 7/9] x86/mm: Handle tagged memory accesses from kernel threads
Date: Fri, 5 Feb 2021 18:16:28 +0300 [thread overview]
Message-ID: <20210205151631.43511-9-kirill.shutemov@linux.intel.com> (raw)
In-Reply-To: <20210205151631.43511-1-kirill.shutemov@linux.intel.com>
When a kernel thread performs memory access on behalf of a process (like
in async I/O, io_uring, etc.) it has to respect tagging setup of the
process as user addresses can include tags.
Normally, LAM setup is per-thread and recorded in thread flags, but for
this use case we also track LAM setup per-mm. mm->context.lam would
record LAM that allows the most tag bits among the threads of the mm.
The info used by switch_mm_irqs_off() to construct CR3 if the task is
kernel thread. Thread flags of the kernel thread get updated according
to mm->context.lam. It allows untagged_addr() to work correctly.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/include/asm/mmu.h | 1 +
arch/x86/mm/tlb.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 9257667d13c5..fb05d6a11538 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -35,6 +35,7 @@ typedef struct {
#ifdef CONFIG_X86_64
/* True if mm supports a task running in 32 bit compatibility mode. */
unsigned short ia32_compat;
+ u8 lam;
#endif
struct mutex lock;
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 138d4748aa97..1f9749da12e4 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -176,6 +176,34 @@ static u8 gen_lam(struct task_struct *tsk, struct mm_struct *mm)
if (!tsk)
return LAM_NONE;
+ if (tsk->flags & PF_KTHREAD) {
+ /*
+ * For kernel thread use the most permissive LAM
+ * used by the mm. It's required to handle kernel thread
+ * memory accesses on behalf of a process.
+ *
+ * Adjust thread flags accodringly, so untagged_addr() would
+ * work correctly.
+ */
+ switch (mm->context.lam) {
+ case LAM_NONE:
+ clear_thread_flag(TIF_LAM_U48);
+ clear_thread_flag(TIF_LAM_U57);
+ return LAM_NONE;
+ case LAM_U57:
+ clear_thread_flag(TIF_LAM_U48);
+ set_thread_flag(TIF_LAM_U57);
+ return LAM_U57;
+ case LAM_U48:
+ set_thread_flag(TIF_LAM_U48);
+ clear_thread_flag(TIF_LAM_U57);
+ return LAM_U48;
+ default:
+ WARN_ON_ONCE(1);
+ return LAM_NONE;
+ }
+ }
+
if (test_ti_thread_flag(ti, TIF_LAM_U57))
return LAM_U57;
if (test_ti_thread_flag(ti, TIF_LAM_U48))
--
2.26.2
next prev parent reply other threads:[~2021-02-05 17:28 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-05 15:16 [RFC 0/9] Linear Address Masking enabling Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 1/9] mm, arm64: Update PR_SET/GET_TAGGED_ADDR_CTRL interface Kirill A. Shutemov
2021-02-11 16:57 ` Catalin Marinas
2021-02-11 17:06 ` Dave Hansen
2021-02-11 18:26 ` Catalin Marinas
2021-02-05 15:16 ` [QEMU] x86: Implement Linear Address Masking support Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 2/9] x86/mm: Fix CR3_ADDR_MASK Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 3/9] x86: CPUID and CR3/CR4 flags for Linear Address Masking Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 4/9] x86/mm: Introduce TIF_LAM_U57 and TIF_LAM_U48 Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 5/9] x86/mm: Provide untagged_addr() helper Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 6/9] x86/uaccess: Remove tags from the address before checking Kirill A. Shutemov
2021-02-05 15:16 ` Kirill A. Shutemov [this message]
2021-02-05 15:16 ` [RFC 8/9] x86/mm: Make LAM_U48 and mappings above 47-bits mutually exclusive Kirill A. Shutemov
2021-02-05 15:16 ` [RFC 9/9] x86/mm: Implement PR_SET/GET_TAGGED_ADDR_CTRL with LAM Kirill A. Shutemov
2021-02-05 15:42 ` H.J. Lu
2021-02-07 8:07 ` Dmitry Vyukov
2021-02-07 14:09 ` Kirill A. Shutemov
2021-02-07 14:11 ` Dmitry Vyukov
2021-02-05 15:16 ` [QEMU] x86: Implement Linear Address Masking support Kirill A. Shutemov
2021-02-05 15:49 ` [RFC 0/9] Linear Address Masking enabling Peter Zijlstra
2021-02-05 16:01 ` Kirill A. Shutemov
2021-02-05 16:19 ` Peter Zijlstra
2021-02-07 8:24 ` Dmitry Vyukov
2021-02-07 14:11 ` Kirill A. Shutemov
2021-09-21 16:52 ` Dmitry Vyukov
2021-09-21 17:15 ` H.J. Lu
2021-09-22 1:15 ` Zhang, Xiang1
2021-09-22 12:54 ` Dmitry Vyukov
2021-09-22 20:03 ` Dmitry Vyukov
2021-09-22 21:33 ` Kirill A. Shutemov
2021-09-23 0:15 ` H.J. Lu
2021-09-23 5:35 ` Dmitry Vyukov
2021-09-23 0:07 ` H.J. Lu
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