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From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com, linux-mm@kvack.org,
	Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
	Minchan Kim <minchan@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Mohamed Alzayat <alzayat@mpi-sws.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Nadav Amit <namit@vmware.com>,
	Andrea Arcangeli <aarcange@redhat.com>
Subject: [PATCH v3 6/6] x86/ldt: Use tlb_gather_mmu_fullmm() when freeing LDT page-tables
Date: Wed, 27 Jan 2021 23:53:47 +0000
Message-ID: <20210127235347.1402-7-will@kernel.org> (raw)
In-Reply-To: <20210127235347.1402-1-will@kernel.org>

free_ldt_pgtables() uses the MMU gather API for batching TLB flushes
over the call to free_pgd_range(). However, tlb_gather_mmu() expects
to operate on user addresses and so passing LDT_{BASE,END}_ADDR will
confuse the range setting logic in __tlb_adjust_range(), causing the
gather to identify a range starting at TASK_SIZE. Such a large range
will be converted into a 'fullmm' flush by the low-level invalidation
code, so change the caller to invoke tlb_gather_mmu_fullmm() directly.

Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/x86/kernel/ldt.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index 7ad9834e0d95..aa15132228da 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -398,7 +398,13 @@ static void free_ldt_pgtables(struct mm_struct *mm)
 	if (!boot_cpu_has(X86_FEATURE_PTI))
 		return;
 
-	tlb_gather_mmu(&tlb, mm);
+	/*
+	 * Although free_pgd_range() is intended for freeing user
+	 * page-tables, it also works out for kernel mappings on x86.
+	 * We use tlb_gather_mmu_fullmm() to avoid confusing the
+	 * range-tracking logic in __tlb_adjust_range().
+	 */
+	tlb_gather_mmu_fullmm(&tlb, mm);
 	free_pgd_range(&tlb, start, end, start, end);
 	tlb_finish_mmu(&tlb);
 #endif
-- 
2.30.0.365.g02bc693789-goog



  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-27 23:53 [PATCH v3 0/6] tlb: Fix (soft-)dirty bit management & clean up API Will Deacon
2021-01-27 23:53 ` [PATCH v3 1/6] mm: proc: Invalidate TLB after clearing soft-dirty page state Will Deacon
2021-01-27 23:53 ` [PATCH v3 2/6] tlb: mmu_gather: Remove unused start/end arguments from tlb_finish_mmu() Will Deacon
2021-01-27 23:53 ` [PATCH v3 3/6] tlb: mmu_gather: Introduce tlb_gather_mmu_fullmm() Will Deacon
2021-01-27 23:53 ` [PATCH v3 4/6] tlb: mmu_gather: Remove start/end arguments from tlb_gather_mmu() Will Deacon
2021-01-27 23:53 ` [PATCH v3 5/6] tlb: arch: Remove empty __tlb_remove_tlb_entry() stubs Will Deacon
2021-01-27 23:53 ` Will Deacon [this message]
2021-01-28 17:14 ` [PATCH v3 0/6] tlb: Fix (soft-)dirty bit management & clean up API Linus Torvalds
2021-01-29 11:09   ` Peter Zijlstra

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