From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bn1bon0063.outbound.protection.outlook.com ([157.56.111.63]:2880 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751451AbcBJWD1 (ORCPT ); Wed, 10 Feb 2016 17:03:27 -0500 From: Jay Cornwall To: CC: Joerg Roedel , Jay Cornwall , Subject: [PATCH] iommu/amd: Apply workaround for ATS write permission check Date: Wed, 10 Feb 2016 15:48:01 -0600 Message-ID: <1455140881-17041-1-git-send-email-jay@jcornwall.me> MIME-Version: 1.0 Content-Type: text/plain Sender: stable-owner@vger.kernel.org List-ID: The AMD Family 15h Models 30h-3Fh (Kaveri) BIOS and Kernel Developer's Guide omitted part of the BIOS IOMMU L2 register setup specification. Without this setup the IOMMU L2 does not fully respect write permissions when handling an ATS translation request. The IOMMU L2 will set PTE dirty bit when handling an ATS translation with write permission request, even when PTE RW bit is clear. This may occur by direct translation (which would cause a PPR) or by prefetch request from the ATC. This is observed in practice when the IOMMU L2 modifies a PTE which maps a pagecache page. The ext4 filesystem driver BUGs when asked to writeback these (non-modified) pages. Enable ATS write permission check in the Kaveri IOMMU L2 if BIOS has not. Signed-off-by: Jay Cornwall Cc: # v3.19+ --- drivers/iommu/amd_iommu_init.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index 013bdff..0c4257e 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -1016,6 +1016,34 @@ static void amd_iommu_erratum_746_workaround(struct amd_iommu *iommu) } /* + * Family15h Model 30h-3fh (IOMMU Mishandles ATS Write Permission) + * Workaround: + * BIOS should enable ATS write permission check by setting + * L2_DEBUG_3[AtsIgnoreIWDis](D0F2xF4_x47[0]) = 1b + */ +static void amd_iommu_ats_write_check_workaround(struct amd_iommu *iommu) +{ + u32 value; + + if ((boot_cpu_data.x86 != 0x15) || + (boot_cpu_data.x86_model < 0x30) || + (boot_cpu_data.x86_model > 0x3f)) + return; + + /* Test L2_DEBUG_3[AtsIgnoreIWDis] == 1 */ + value = iommu_read_l2(iommu, 0x47); + + if (value & BIT(0)) + return; + + /* Set L2_DEBUG_3[AtsIgnoreIWDis] = 1 */ + iommu_write_l2(iommu, 0x47, value | BIT(0)); + + pr_info("AMD-Vi: Applying ATS write check workaround for IOMMU at %s\n", + dev_name(&iommu->dev->dev)); +} + +/* * This function clues the initialization function for one IOMMU * together and also allocates the command buffer and programs the * hardware. It does NOT enable the IOMMU. This is done afterwards. @@ -1284,6 +1312,7 @@ static int iommu_init_pci(struct amd_iommu *iommu) } amd_iommu_erratum_746_workaround(iommu); + amd_iommu_ats_write_check_workaround(iommu); iommu->iommu_dev = iommu_device_create(&iommu->dev->dev, iommu, amd_iommu_groups, "ivhd%d", -- 1.9.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jay Cornwall Subject: [PATCH] iommu/amd: Apply workaround for ATS write permission check Date: Wed, 10 Feb 2016 15:48:01 -0600 Message-ID: <1455140881-17041-1-git-send-email-jay@jcornwall.me> Mime-Version: 1.0 Content-Type: text/plain Return-path: Sender: stable-owner@vger.kernel.org To: iommu@lists.linux-foundation.org Cc: Joerg Roedel , Jay Cornwall , stable@vger.kernel.org List-Id: iommu@lists.linux-foundation.org The AMD Family 15h Models 30h-3Fh (Kaveri) BIOS and Kernel Developer's Guide omitted part of the BIOS IOMMU L2 register setup specification. Without this setup the IOMMU L2 does not fully respect write permissions when handling an ATS translation request. The IOMMU L2 will set PTE dirty bit when handling an ATS translation with write permission request, even when PTE RW bit is clear. This may occur by direct translation (which would cause a PPR) or by prefetch request from the ATC. This is observed in practice when the IOMMU L2 modifies a PTE which maps a pagecache page. The ext4 filesystem driver BUGs when asked to writeback these (non-modified) pages. Enable ATS write permission check in the Kaveri IOMMU L2 if BIOS has not. Signed-off-by: Jay Cornwall Cc: # v3.19+ --- drivers/iommu/amd_iommu_init.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c index 013bdff..0c4257e 100644 --- a/drivers/iommu/amd_iommu_init.c +++ b/drivers/iommu/amd_iommu_init.c @@ -1016,6 +1016,34 @@ static void amd_iommu_erratum_746_workaround(struct amd_iommu *iommu) } /* + * Family15h Model 30h-3fh (IOMMU Mishandles ATS Write Permission) + * Workaround: + * BIOS should enable ATS write permission check by setting + * L2_DEBUG_3[AtsIgnoreIWDis](D0F2xF4_x47[0]) = 1b + */ +static void amd_iommu_ats_write_check_workaround(struct amd_iommu *iommu) +{ + u32 value; + + if ((boot_cpu_data.x86 != 0x15) || + (boot_cpu_data.x86_model < 0x30) || + (boot_cpu_data.x86_model > 0x3f)) + return; + + /* Test L2_DEBUG_3[AtsIgnoreIWDis] == 1 */ + value = iommu_read_l2(iommu, 0x47); + + if (value & BIT(0)) + return; + + /* Set L2_DEBUG_3[AtsIgnoreIWDis] = 1 */ + iommu_write_l2(iommu, 0x47, value | BIT(0)); + + pr_info("AMD-Vi: Applying ATS write check workaround for IOMMU at %s\n", + dev_name(&iommu->dev->dev)); +} + +/* * This function clues the initialization function for one IOMMU * together and also allocates the command buffer and programs the * hardware. It does NOT enable the IOMMU. This is done afterwards. @@ -1284,6 +1312,7 @@ static int iommu_init_pci(struct amd_iommu *iommu) } amd_iommu_erratum_746_workaround(iommu); + amd_iommu_ats_write_check_workaround(iommu); iommu->iommu_dev = iommu_device_create(&iommu->dev->dev, iommu, amd_iommu_groups, "ivhd%d", -- 1.9.1