Messages in this thread | | | Subject | Re: [PATCH] iommu/vt-d: remove redundant variable no_platform_optin | From | Lu Baolu <> | Date | Thu, 5 Nov 2020 09:40:37 +0800 |
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Hi Zhenzhong,
On 11/4/20 4:19 PM, Zhenzhong Duan wrote: > no_platform_optin is redundant with dmar_disabled and it's only used in > platform_optin_force_iommu(), remove it and use dmar_disabled instead.
It's actually not.
If CONFIG_INTEL_IOMMU_DEFAULT_ON is not set, we will get "dmar_disable = 1" and "no_platform_optin = 0". In this case, we must force the iommu on and set dmar_disable = 0.
The real use case: if a kernel built with [CONFIG_INTEL_IOMMU_DEFAULT_ON = n] running on a platform with thunderbolt ports, we must force IOMMU on so that the system could be protected from possible malicious peripherals.
Best regards, baolu
> > Meanwhile remove all the dead code in platform_optin_force_iommu(). > > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com> > --- > drivers/iommu/intel/iommu.c | 14 ++------------ > 1 file changed, 2 insertions(+), 12 deletions(-) > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index 8651f6d4dfa0..a011d1ed63ef 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -180,7 +180,6 @@ static int rwbf_quirk; > */ > static int force_on = 0; > int intel_iommu_tboot_noforce; > -static int no_platform_optin; > > #define ROOT_ENTRY_NR (VTD_PAGE_SIZE/sizeof(struct root_entry)) > > @@ -440,7 +439,6 @@ static int __init intel_iommu_setup(char *str) > pr_info("IOMMU enabled\n"); > } else if (!strncmp(str, "off", 3)) { > dmar_disabled = 1; > - no_platform_optin = 1; > pr_info("IOMMU disabled\n"); > } else if (!strncmp(str, "igfx_off", 8)) { > dmar_map_gfx = 0; > @@ -4810,20 +4808,12 @@ static inline bool has_external_pci(void) > > static int __init platform_optin_force_iommu(void) > { > - if (!dmar_platform_optin() || no_platform_optin || !has_external_pci()) > + if (!dmar_platform_optin() || dmar_disabled || !has_external_pci()) > return 0; > > - if (no_iommu || dmar_disabled) > + if (no_iommu) > pr_info("Intel-IOMMU force enabled due to platform opt in\n"); > > - /* > - * If Intel-IOMMU is disabled by default, we will apply identity > - * map for all devices except those marked as being untrusted. > - */ > - if (dmar_disabled) > - iommu_set_default_passthrough(false); > - > - dmar_disabled = 0; > no_iommu = 0; > > return 1; >
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