[PATCH 4/3] iommu/io-pgtable: Rationalise quirk handling
Robin Murphy
robin.murphy at arm.com
Fri Feb 12 07:23:04 PST 2016
On 12/02/16 12:32, Laurent Pinchart wrote:
> On Friday 12 February 2016 12:08:58 Will Deacon wrote:
>> On Thu, Feb 11, 2016 at 04:13:45PM +0000, Robin Murphy wrote:
>>> As the number of io-pgtable implementations grows beyond 1, it's time
>>> to rationalise the quirks mechanism before things have a chance to
>>> start getting really ugly and out-of-hand.
>>>
>>> To that end:
>>> - Indicate exactly which quirks each format can/does support.
>>> - Fail creating a table if a caller wants unsupported quirks.
>>> - Properly document where each quirk applies and why.
>>>
>>> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
>>> ---
>>>
>>> drivers/iommu/io-pgtable-arm-v7s.c | 3 +++
>>> drivers/iommu/io-pgtable-arm.c | 2 ++
>>> drivers/iommu/io-pgtable.c | 3 +++
>>> drivers/iommu/io-pgtable.h | 24 ++++++++++++++++++++----
>>> 4 files changed, 28 insertions(+), 4 deletions(-)
>>
>> Note that I can't merge this until we've figured out the plan for Yong's
>> driver.
Indeed (hence 4/3) - it just ended up seeming like a significant enough
change to warrant its own patch, but not critical enough to warrant
splitting it for the sake of applying the parts touching the existing
code right now.
>>> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c
>>> b/drivers/iommu/io-pgtable-arm-v7s.c index d39a021..9bc607a 100644
>>> --- a/drivers/iommu/io-pgtable-arm-v7s.c
>>> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
>>>
>>> @@ -690,6 +690,9 @@ out_free_data:
>>> struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns = {
>>>
>>> .alloc = arm_v7s_alloc_pgtable,
>>> .free = arm_v7s_free_pgtable,
>>>
>>> + .supported_quirks = IO_PGTABLE_QUIRK_ARM_NS |
>>> + IO_PGTABLE_QUIRK_NO_PERMS |
>>> + IO_PGTABLE_QUIRK_TLBI_ON_MAP,
>>>
>>> };
>>>
>>> #ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
>>>
>>> diff --git a/drivers/iommu/io-pgtable-arm.c
>>> b/drivers/iommu/io-pgtable-arm.c index 4095af2..32f94f1 100644
>>> --- a/drivers/iommu/io-pgtable-arm.c
>>> +++ b/drivers/iommu/io-pgtable-arm.c
>>> @@ -863,6 +863,7 @@ arm_32_lpae_alloc_pgtable_s2(struct io_pgtable_cfg
>>> *cfg, void *cookie)>
>>> struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s1_init_fns = {
>>>
>>> .alloc = arm_64_lpae_alloc_pgtable_s1,
>>> .free = arm_lpae_free_pgtable,
>>>
>>> + .supported_quirks = IO_PGTABLE_QUIRK_ARM_NS,
>>>
>>> };
>>>
>>> struct io_pgtable_init_fns io_pgtable_arm_64_lpae_s2_init_fns = {
>>>
>>> @@ -873,6 +874,7 @@ struct io_pgtable_init_fns
>>> io_pgtable_arm_64_lpae_s2_init_fns = {>
>>> struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns = {
>>>
>>> .alloc = arm_32_lpae_alloc_pgtable_s1,
>>> .free = arm_lpae_free_pgtable,
>>>
>>> + .supported_quirks = IO_PGTABLE_QUIRK_ARM_NS,
>>>
>>> };
>>>
>>> struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s2_init_fns = {
>>>
>>> diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
>>> index 876f6a7..0f57a45 100644
>>> --- a/drivers/iommu/io-pgtable.c
>>> +++ b/drivers/iommu/io-pgtable.c
>>> @@ -52,6 +52,9 @@ struct io_pgtable_ops *alloc_io_pgtable_ops(enum
>>> io_pgtable_fmt fmt,>
>>> if (!fns)
>>>
>>> return NULL;
>>>
>>> + if (cfg->quirks & ~fns->supported_quirks)
>>> + return NULL;
>>> +
>>>
>>> iop = fns->alloc(cfg, cookie);
>>> if (!iop)
>>>
>>> return NULL;
>>>
>>> diff --git a/drivers/iommu/io-pgtable.h b/drivers/iommu/io-pgtable.h
>>> index 4faee7d..6e7f11e 100644
>>> --- a/drivers/iommu/io-pgtable.h
>>> +++ b/drivers/iommu/io-pgtable.h
>>> @@ -47,10 +47,24 @@ struct iommu_gather_ops {
>>>
>>> * page table walker.
>>> */
>>>
>>> struct io_pgtable_cfg {
>>>
>>> - #define IO_PGTABLE_QUIRK_ARM_NS BIT(0) /* Set NS bit in PTEs */
>>> - #define IO_PGTABLE_QUIRK_NO_PERMS BIT(1) /* No AP/XN bits */
>>> - #define IO_PGTABLE_QUIRK_TLBI_ON_MAP BIT(2) /* TLB Inv. on map */
>>> - int quirks;
>>> + /*
>>> + * IO_PGTABLE_QUIRK_ARM_NS: (ARM formats) Set NS and NSTABLE bits in
>>> + * stage 1 PTEs, for hardware which insists on validating them
>>> + * even in non-secure state where they should normally be ignored.
>>> + *
>>> + * IO_PGTABLE_QUIRK_NO_PERMS: Ignore the IOMMU_READ, IOMMU_WRITE and
>>> + * IOMMU_NOEXEC flags and map everything with full access, for
>>> + * hardware which does not implement the permissions of a given
>>> + * format, and/or requires some format-specific default value.
>>> + *
>>> + * IO_PGTABLE_QUIRK_TLBI_ON_MAP: If the format forbids caching
> invalid
>>> + * (unmapped) entries but the hardware might do so anyway, perform
>>> + * TLB maintenance when mapping as well as when unmapping.
>>> + */
>>
>> Much better, cheers.
>>
>>> + #define IO_PGTABLE_QUIRK_ARM_NS BIT(0)
>>> + #define IO_PGTABLE_QUIRK_NO_PERMS BIT(1)
>>> + #define IO_PGTABLE_QUIRK_TLBI_ON_MAP BIT(2)
>>> + unsigned int quirks;
>>
>> Let's just make this unsigned long.
>>
>>> unsigned long pgsize_bitmap;
>>> unsigned int ias;
>>> unsigned int oas;
>>>
>>> @@ -173,10 +187,12 @@ static inline void io_pgtable_tlb_sync(struct
>>> io_pgtable *iop)
>>> *
>>> * @alloc: Allocate a set of page tables described by cfg.
>>> * @free: Free the page tables associated with iop.
>>> + * @supported_quirks: Bitmap of quirks supported by the format.
>>> */
>>> struct io_pgtable_init_fns {
>>> struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void
> *cookie);
>>> void (*free)(struct io_pgtable *iop);
>>> + unsigned int supported_quirks;
>>> };
>>
>> My only gripe here is that this is supposed to be a struct of function
>> pointers... get_supported_quirks() ?
>
> Can't we instead say it's a struct of function pointers and static data ? :-)
> A function to retrieve the supported quirks will just contribute to kernel
> bloat without adding any extra benefit.
Bleh - personally I think it's marginally more obvious and readable to
have the information looking like data, but I'd much sooner just have a
hard-coded "if (cfq->quirks & ..." check in every format's alloc
function than introduce a whole new callback. Does that sound like a
reasonable compromise?
Robin.
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