From: Robin Murphy <robin.murphy@arm.com>
To: Steven Price <steven.price@arm.com>,
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org,
iommu@lists.linux-foundation.org
Cc: linuxarm@huawei.com, lorenzo.pieralisi@arm.com, joro@8bytes.org,
wanghuiqiang@huawei.com, guohanjun@huawei.com,
Sami.Mujawar@arm.com, jon@solid-run.com, eric.auger@redhat.com
Subject: Re: [PATCH v3 09/10] iommu/arm-smmu: Get associated RMR info and install bypass SMR
Date: Fri, 7 May 2021 10:52:39 +0100 [thread overview]
Message-ID: <8c7dad26-b286-3974-9316-78ce1129ebe3@arm.com> (raw)
In-Reply-To: <501cd986-7f9c-9aa7-b4e9-f2ef98fb7a95@arm.com>
On 2021-05-06 16:17, Steven Price wrote:
> On 20/04/2021 09:27, Shameer Kolothum wrote:
>> From: Jon Nettleton <jon@solid-run.com>
>>
>> Check if there is any RMR info associated with the devices behind
>> the SMMU and if any, install bypass SMRs for them. This is to
>> keep any ongoing traffic associated with these devices alive
>> when we enable/reset SMMU during probe().
>>
>> Signed-off-by: Jon Nettleton <jon@solid-run.com>
>> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
>> ---
>> drivers/iommu/arm/arm-smmu/arm-smmu.c | 42 +++++++++++++++++++++++++++
>> drivers/iommu/arm/arm-smmu/arm-smmu.h | 2 ++
>> 2 files changed, 44 insertions(+)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> index d8c6bfde6a61..4d2f91626d87 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
>> @@ -2102,6 +2102,43 @@ err_reset_platform_ops: __maybe_unused;
>> return err;
>> }
>> +static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device
>> *smmu)
>> +{
>> + struct iommu_rmr *e;
>> + int i, cnt = 0;
>> + u32 smr;
>> +
>> + for (i = 0; i < smmu->num_mapping_groups; i++) {
>> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
>> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
>> + continue;
>> +
>> + list_for_each_entry(e, &smmu->rmr_list, list) {
>> + if (FIELD_GET(ARM_SMMU_SMR_ID, smr) != e->sid)
>> + continue;
>> +
>> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
>> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
>> + smmu->smrs[i].valid = true;
>> +
>> + smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
>> + smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
>> + smmu->s2crs[i].cbndx = 0xff;
>> +
>> + cnt++;
>> + }
>> + }
>
> If I understand this correctly - this is looking at the current
> (hardware) configuration of the SMMU and attempting to preserve any
> bypass SMRs. However from what I can tell it suffers from the following
> two problems:
>
> (a) Only the ID of the SMR is being checked, not the MASK. So if the
> firmware has setup an SMR matching a number of streams this will break.
>
> (b) The SMMU might not be enabled at all (CLIENTPD==1) or bypass
> enabled for unmatched streams (USFCFG==0).
Yes, trying to infer anything from the current SMMU hardware state is
bogus - consider what you might find left over after a kexec, for
instance. The *only* way to detect the presence and applicability of
RMRs is to look at the actual RMR nodes in the IORT.
Ignore what we let the Qualcomm ACPI bootloader hack do - that whole
implementation is "special".
Robin.
> Certainly in my test setup case (b) applies and so this doesn't work.
> Perhaps something like the below would work better? (It works in the
> case of the SMMU not enabled - I've not tested case (a)).
>
> Steve
>
> ----8<----
> static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device *smmu)
> {
> struct iommu_rmr *e;
> int i, cnt = 0;
> u32 smr;
> u32 reg;
>
> reg = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_sCR0);
>
> if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
> /*
> * SMMU is already enabled and disallowing bypass, so preserve
> * the existing SMRs
> */
> for (i = 0; i < smmu->num_mapping_groups; i++) {
> smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
> if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
> continue;
> smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
> smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
> smmu->smrs[i].valid = true;
> }
> }
>
> list_for_each_entry(e, &smmu->rmr_list, list) {
> u32 sid = e->sid;
>
> i = arm_smmu_find_sme(smmu, sid, ~0);
> if (i < 0)
> continue;
> if (smmu->s2crs[i].count == 0) {
> smmu->smrs[i].id = sid;
> smmu->smrs[i].mask = ~0;
> smmu->smrs[i].valid = true;
> }
> smmu->s2crs[i].count++;
> smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
> smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
> smmu->s2crs[i].cbndx = 0xff;
>
> cnt++;
> }
>
> if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
> /* Remove the valid bit for unused SMRs */
> for (i = 0; i < smmu->num_mapping_groups; i++) {
> if (smmu->s2crs[i].count == 0)
> smmu->smrs[i].valid = false;
> }
> }
>
> dev_notice(smmu->dev, "\tpreserved %d boot mapping%s\n", cnt,
> cnt == 1 ? "" : "s");
> }
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next prev parent reply other threads:[~2021-05-07 9:54 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 8:27 [PATCH v3 00/10] ACPI/IORT: Support for IORT RMR node Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 01/10] ACPI/IORT: Add support for RMR node parsing Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 02/10] iommu/dma: Introduce generic helper to retrieve RMR info Shameer Kolothum
2021-04-20 12:04 ` kernel test robot
2021-04-20 12:32 ` kernel test robot
2021-04-20 12:59 ` kernel test robot
2021-04-20 8:27 ` [PATCH v3 03/10] ACPI/IORT: Add a helper to retrieve RMR memory regions Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 04/10] iommu/dma: Add a helper function to reserve RMRs for IOMMU drivers Shameer Kolothum
2021-04-20 12:07 ` kernel test robot
2021-04-20 13:32 ` kernel test robot
2021-04-20 8:27 ` [PATCH v3 05/10] iommu/arm-smmu-v3: Introduce strtab init helper Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 06/10] iommu/arm-smmu-v3: Add bypass flag to arm_smmu_write_strtab_ent() Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 07/10] iommu/arm-smmu-v3: Get associated RMR info and install bypass STE Shameer Kolothum
2021-04-20 8:27 ` [PATCH v3 08/10] iommu/arm-smmu-v3: Reserve any RMR regions associated with a dev Shameer Kolothum
2021-05-07 10:01 ` Robin Murphy
2021-05-10 9:19 ` Shameerali Kolothum Thodi
2021-05-10 14:22 ` Robin Murphy
2021-04-20 8:27 ` [PATCH v3 09/10] iommu/arm-smmu: Get associated RMR info and install bypass SMR Shameer Kolothum
2021-05-06 15:17 ` Steven Price
2021-05-07 9:52 ` Robin Murphy [this message]
2021-05-10 8:40 ` Shameerali Kolothum Thodi
2021-05-10 11:51 ` Jon Nettleton
2021-04-20 8:27 ` [PATCH v3 10/10] iommu/arm-smmu: Reserve any RMR regions associated with a dev Shameer Kolothum
2021-04-20 14:18 ` kernel test robot
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