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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>, linux-kernel@vger.kernel.org
Subject: [PATCH 5/5] efi: permit calling efi_mem_reserve_persistent from atomic context
Date: Wed, 14 Nov 2018 09:55:44 -0800
Message-ID: <20181114175544.12860-6-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <20181114175544.12860-1-ard.biesheuvel@linaro.org>

Currently, efi_mem_reserve_persistent() may not be called from atomic
context, since both the kmalloc() call and the memremap() call may
sleep.

The kmalloc() call is easy enough to fix, but the memremap() call
needs to be moved into an init hook since we cannot control the
memory allocation behavior of memremap() at the call site.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/efi.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 72a4da76d274..fad7c62cfc0e 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -967,36 +967,43 @@ bool efi_is_table_address(unsigned long phys_addr)
 }
 
 static DEFINE_SPINLOCK(efi_mem_reserve_persistent_lock);
+static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
 
 int efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
 {
-	struct linux_efi_memreserve *rsv, *parent;
+	struct linux_efi_memreserve *rsv;
 
-	if (efi.mem_reserve == EFI_INVALID_TABLE_ADDR)
+	if (!efi_memreserve_root)
 		return -ENODEV;
 
-	rsv = kmalloc(sizeof(*rsv), GFP_KERNEL);
+	rsv = kmalloc(sizeof(*rsv), GFP_ATOMIC);
 	if (!rsv)
 		return -ENOMEM;
 
-	parent = memremap(efi.mem_reserve, sizeof(*rsv), MEMREMAP_WB);
-	if (!parent) {
-		kfree(rsv);
-		return -ENOMEM;
-	}
-
 	rsv->base = addr;
 	rsv->size = size;
 
 	spin_lock(&efi_mem_reserve_persistent_lock);
-	rsv->next = parent->next;
-	parent->next = __pa(rsv);
+	rsv->next = efi_memreserve_root->next;
+	efi_memreserve_root->next = __pa(rsv);
 	spin_unlock(&efi_mem_reserve_persistent_lock);
 
-	memunmap(parent);
+	return 0;
+}
 
+static int __init efi_memreserve_root_init(void)
+{
+	if (efi.mem_reserve == EFI_INVALID_TABLE_ADDR)
+		return -ENODEV;
+
+	efi_memreserve_root = memremap(efi.mem_reserve,
+				       sizeof(*efi_memreserve_root),
+				       MEMREMAP_WB);
+	if (!efi_memreserve_root)
+		return -ENOMEM;
 	return 0;
 }
+early_initcall(efi_memreserve_root_init);
 
 #ifdef CONFIG_KEXEC
 static int update_efi_random_seed(struct notifier_block *nb,
-- 
2.17.1

  parent reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14 17:55 [GIT PULL 0/5] EFI fixes for v4.20 Ard Biesheuvel
2018-11-14 17:55 ` [PATCH 1/5] efi: Fix debugobjects warning on efi_rts_work Ard Biesheuvel
2018-11-14 17:55 ` [PATCH 2/5] efi: arm: revert deferred unmap of early memmap mapping Ard Biesheuvel
2018-11-14 17:55 ` [PATCH 3/5] efi/arm: libstub: pack FDT after populating it Ard Biesheuvel
2018-11-14 17:55 ` [PATCH 4/5] efi/arm: defer persistent reservations until after paging_init() Ard Biesheuvel
2018-11-14 17:55 ` Ard Biesheuvel [this message]
2018-11-27 18:59   ` [PATCH 5/5] efi: permit calling efi_mem_reserve_persistent from atomic context Jeremy Linton
2018-11-27 19:16     ` Ard Biesheuvel

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