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SubjectRe: [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict()
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On 6/16/21 7:03 PM, John Garry wrote:
> We only ever now set strict mode enabled in iommu_set_dma_strict(), so
> just remove the argument.
>
> Signed-off-by: John Garry <john.garry@huawei.com>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/iommu/amd/init.c | 2 +-
> drivers/iommu/intel/iommu.c | 6 +++---
> drivers/iommu/iommu.c | 5 ++---
> include/linux/iommu.h | 2 +-
> 4 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index fb3618af643b..7bc460052678 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -3099,7 +3099,7 @@ static int __init parse_amd_iommu_options(char *str)
> for (; *str; ++str) {
> if (strncmp(str, "fullflush", 9) == 0) {
> pr_warn("amd_iommu=fullflush deprecated; use iommu.strict instead\n");
> - iommu_set_dma_strict(true);
> + iommu_set_dma_strict();
> }
> if (strncmp(str, "force_enable", 12) == 0)
> amd_iommu_force_enable = true;
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index d586990fa751..0618c35cfb51 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -454,7 +454,7 @@ static int __init intel_iommu_setup(char *str)
> iommu_dma_forcedac = true;
> } else if (!strncmp(str, "strict", 6)) {
> pr_warn("intel_iommu=strict deprecated; use iommu.strict instead\n");
> - iommu_set_dma_strict(true);
> + iommu_set_dma_strict();
> } else if (!strncmp(str, "sp_off", 6)) {
> pr_info("Disable supported super page\n");
> intel_iommu_superpage = 0;
> @@ -4382,7 +4382,7 @@ int __init intel_iommu_init(void)
> */
> if (cap_caching_mode(iommu->cap)) {
> pr_warn("IOMMU batching disallowed due to virtualization\n");
> - iommu_set_dma_strict(true);
> + iommu_set_dma_strict();
> }
> iommu_device_sysfs_add(&iommu->iommu, NULL,
> intel_iommu_groups,
> @@ -5699,7 +5699,7 @@ static void quirk_calpella_no_shadow_gtt(struct pci_dev *dev)
> } else if (dmar_map_gfx) {
> /* we have to ensure the gfx device is idle before we flush */
> pci_info(dev, "Disabling batched IOTLB flush on Ironlake\n");
> - iommu_set_dma_strict(true);
> + iommu_set_dma_strict();
> }
> }
> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0040, quirk_calpella_no_shadow_gtt);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 60b1ec42e73b..ff221d3ddcbc 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str)
> }
> early_param("iommu.strict", iommu_dma_setup);
>
> -void iommu_set_dma_strict(bool strict)
> +void iommu_set_dma_strict(void)
> {
> - if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT))
> - iommu_dma_strict = strict;
> + iommu_dma_strict = true;

Sorry, I still can't get how iommu.strict kernel option works.

static int __init iommu_dma_setup(char *str)
{
int ret = kstrtobool(str, &iommu_dma_strict);

if (!ret)
iommu_cmd_line |= IOMMU_CMD_LINE_STRICT;
return ret;
}
early_param("iommu.strict", iommu_dma_setup);

The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere. Hence,
I am wondering how could it work? A bug or I missed anything?

Best regards,
baolu

> }
>
> bool iommu_get_dma_strict(struct iommu_domain *domain)
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 32d448050bf7..754f67d6dd90 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -476,7 +476,7 @@ int iommu_enable_nesting(struct iommu_domain *domain);
> int iommu_set_pgtable_quirks(struct iommu_domain *domain,
> unsigned long quirks);
>
> -void iommu_set_dma_strict(bool val);
> +void iommu_set_dma_strict(void);
> bool iommu_get_dma_strict(struct iommu_domain *domain);
>
> extern int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
>

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