From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752649AbeBWW30 (ORCPT ); Fri, 23 Feb 2018 17:29:26 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:41818 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751959AbeBWW2R (ORCPT ); Fri, 23 Feb 2018 17:28:17 -0500 From: Sebastian Andrzej Siewior To: iommu@lists.linux-foundation.org Cc: linux-kernel@vger.kernel.org, Joerg Roedel , tglx@linutronix.de, Sebastian Andrzej Siewior Subject: [PATCH 08/10] iommu/amd: drop the lock while allocating new irq remap table Date: Fri, 23 Feb 2018 23:27:34 +0100 Message-Id: <20180223222736.18542-9-bigeasy@linutronix.de> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180223222736.18542-1-bigeasy@linutronix.de> References: <20180223222736.18542-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The irq_remap_table is allocated while the iommu_table_lock is held with interrupts disabled. While this works it makes RT scream very loudly. >>From looking at the call sites, all callers are in the early device initialisation (apic_bsp_setup(), pci_enable_device(), pci_enable_msi()) so make sense to drop the lock which also enables interrupts and try to allocate that memory with GFP_KERNEL instead GFP_ATOMIC. Since during the allocation the iommu_table_lock is dropped, we need to recheck if table exists after the lock has been reacquired. I *think* that it is impossible that the "devid" entry appears in irq_lookup_table while the lock is dropped since the same device can only be probed once. It is more likely that another device added an `alias' entry. However I check for both cases, just to be sure. Signed-off-by: Sebastian Andrzej Siewior --- drivers/iommu/amd_iommu.c | 65 +++++++++++++++++++++++++++++++++----------= ---- 1 file changed, 46 insertions(+), 19 deletions(-) diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index b763fcbd790d..de6cc41d6cd2 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -3588,6 +3588,30 @@ static void set_dte_irq_entry(u16 devid, struct irq_= remap_table *table) amd_iommu_dev_table[devid].data[2] =3D dte; } =20 +static struct irq_remap_table *alloc_irq_table(void) +{ + struct irq_remap_table *table; + + table =3D kzalloc(sizeof(*table), GFP_ATOMIC); + if (!table) + return NULL; + + table->table =3D kmem_cache_alloc(amd_iommu_irq_cache, GFP_KERNEL); + if (!table->table) { + kfree(table); + return NULL; + } + spin_lock_init(&table->lock); + + if (!AMD_IOMMU_GUEST_IR_GA(amd_iommu_guest_ir)) + memset(table->table, 0, + MAX_IRQS_PER_TABLE * sizeof(u32)); + else + memset(table->table, 0, + (MAX_IRQS_PER_TABLE * (sizeof(u64) * 2))); + return table; +} + static void set_remap_table_entry(struct amd_iommu *iommu, u16 devid, struct irq_remap_table *table) { @@ -3599,6 +3623,7 @@ static void set_remap_table_entry(struct amd_iommu *i= ommu, u16 devid, static struct irq_remap_table *get_irq_table(u16 devid) { struct irq_remap_table *table =3D NULL; + struct irq_remap_table *new_table =3D NULL; struct amd_iommu *iommu; unsigned long flags; u16 alias; @@ -3617,42 +3642,44 @@ static struct irq_remap_table *get_irq_table(u16 de= vid) table =3D irq_lookup_table[alias]; if (table) { set_remap_table_entry(iommu, devid, table); - goto out; + goto out_wait; } + raw_spin_unlock_irqrestore(&iommu_table_lock, flags); =20 /* Nothing there yet, allocate new irq remapping table */ - table =3D kzalloc(sizeof(*table), GFP_ATOMIC); - if (!table) + new_table =3D alloc_irq_table(); + if (!new_table) + return NULL; + + raw_spin_lock_irqsave(&iommu_table_lock, flags); + + table =3D irq_lookup_table[devid]; + if (table) goto out_unlock; =20 - /* Initialize table spin-lock */ - spin_lock_init(&table->lock); - - table->table =3D kmem_cache_alloc(amd_iommu_irq_cache, GFP_ATOMIC); - if (!table->table) { - kfree(table); - table =3D NULL; - goto out_unlock; + table =3D irq_lookup_table[alias]; + if (table) { + set_remap_table_entry(iommu, devid, table); + goto out_wait; } =20 - if (!AMD_IOMMU_GUEST_IR_GA(amd_iommu_guest_ir)) - memset(table->table, 0, - MAX_IRQS_PER_TABLE * sizeof(u32)); - else - memset(table->table, 0, - (MAX_IRQS_PER_TABLE * (sizeof(u64) * 2))); - + table =3D new_table; + new_table =3D NULL; =20 set_remap_table_entry(iommu, devid, table); if (devid !=3D alias) set_remap_table_entry(iommu, alias, table); =20 -out: +out_wait: iommu_completion_wait(iommu); =20 out_unlock: raw_spin_unlock_irqrestore(&iommu_table_lock, flags); =20 + if (new_table) { + kmem_cache_free(amd_iommu_irq_cache, new_table->table); + kfree(new_table); + } return table; } =20 --=20 2.16.1