From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Leizhen (ThunderTown)" Subject: Re: [PATCH v4 5/5] iommu/arm-smmu-v3: add bootup option "arm_iommu" Date: Mon, 13 Aug 2018 15:50:17 +0800 Message-ID: <5B713839.1010609@huawei.com> References: <1533558424-16748-1-git-send-email-thunder.leizhen@huawei.com> <1533558424-16748-6-git-send-email-thunder.leizhen@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Robin Murphy , Will Deacon , Joerg Roedel , linux-arm-kernel , iommu , linux-kernel Cc: LinuxArm , Hanjun Guo , Libin List-Id: iommu@lists.linux-foundation.org On 2018/8/9 19:08, Robin Murphy wrote: > On 06/08/18 13:27, Zhen Lei wrote: >> Add a bootup option to make the system manager can choose which mode to >> be used. The default mode is strict. >> >> Signed-off-by: Zhen Lei >> --- >> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ >> drivers/iommu/arm-smmu-v3.c | 17 ++++++++++++++++- >> 2 files changed, 25 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index 533ff5c..426e989 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -1720,6 +1720,15 @@ >> nobypass [PPC/POWERNV] >> Disable IOMMU bypass, using IOMMU for PCI devices. >> >> + arm_iommu= [ARM64] >> + non-strict [Default Off] > > Again, I'd much rather have "iommu.non_strict= { "0" | "1" }" in line with the passthrough option. OK，I will change it in the next version. > > Robin. > >> + Put off TLBs invalidation and release memory first. >> + It's good for scatter-gather performance but lacks full >> + isolation, an untrusted device can access the reused >> + memory because the TLBs may still valid. Please take >> + full consideration before choosing this mode. >> + Note that, VFIO will always use strict mode. >> + >> iommu.passthrough= >> [ARM64] Configure DMA to bypass the IOMMU by default. >> Format: { "0" | "1" } >> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c >> index 904bc1e..9a30892 100644 >> --- a/drivers/iommu/arm-smmu-v3.c >> +++ b/drivers/iommu/arm-smmu-v3.c >> @@ -631,6 +631,21 @@ struct arm_smmu_option_prop { >> { 0, NULL}, >> }; >> >> +static u32 smmu_non_strict __read_mostly; >> + >> +static int __init arm_smmu_setup(char *str) >> +{ >> + if (!strncmp(str, "non-strict", 10)) { >> + smmu_non_strict = 1; >> + pr_warn("WARNING: iommu non-strict mode is chosen.\n" >> + "It's good for scatter-gather performance but lacks full isolation\n"); >> + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); >> + } >> + >> + return 0; >> +} >> +early_param("arm_iommu", arm_smmu_setup); >> + >> static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset, >> struct arm_smmu_device *smmu) >> { >> @@ -1622,7 +1637,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain) >> if (smmu->features & ARM_SMMU_FEAT_COHERENCY) >> pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_NO_DMA; >> >> - if (domain->type == IOMMU_DOMAIN_DMA) { >> + if ((domain->type == IOMMU_DOMAIN_DMA) && smmu_non_strict) { >> domain->non_strict = 1; >> pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT; >> } >> -- >> 1.8.3 >> >> > > . > -- Thanks! BestRegards