From: Will Deacon <will@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 06/10] iommu/io-pgtable-arm: Simplify level indexing
Date: Mon, 4 Nov 2019 18:17:23 +0000 [thread overview]
Message-ID: <20191104181722.GF24909@willie-the-truck> (raw)
In-Reply-To: <698173b487383735e470a28e5cca4f9db22703de.1572024120.git.robin.murphy@arm.com>
On Fri, Oct 25, 2019 at 07:08:35PM +0100, Robin Murphy wrote:
> The nature of the LPAE format means that data->pg_shift is always
> redundant with data->bits_per_level, since they represent the size of a
> page and the number of PTEs per page respectively, and the size of a PTE
> is constant. Thus it works out more efficient to only store the latter,
> and derive the former via a trivial addition where necessary.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> drivers/iommu/io-pgtable-arm.c | 29 +++++++++++++----------------
> 1 file changed, 13 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 4b1483eb0ccf..15b4927ce36b 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -36,10 +36,11 @@
> * in a virtual address mapped by the pagetable in d.
> */
> #define ARM_LPAE_LVL_SHIFT(l,d) \
> - (((ARM_LPAE_MAX_LEVELS - 1 - (l)) * (d)->bits_per_level) + \
> - (d)->pg_shift)
> + (((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level) + \
> + ilog2(sizeof(arm_lpae_iopte)))
>
> -#define ARM_LPAE_GRANULE(d) (1UL << (d)->pg_shift)
> +#define ARM_LPAE_GRANULE(d) \
> + (sizeof(arm_lpae_iopte) << (d)->bits_per_level)
> #define ARM_LPAE_PGD_SIZE(d) \
> (sizeof(arm_lpae_iopte) << (d)->pgd_bits)
>
> @@ -55,9 +56,7 @@
> ((1 << ((d)->bits_per_level + ARM_LPAE_PGD_IDX(l,d))) - 1))
>
> /* Calculate the block/page mapping size at level l for pagetable in d. */
> -#define ARM_LPAE_BLOCK_SIZE(l,d) \
> - (1ULL << (ilog2(sizeof(arm_lpae_iopte)) + \
> - ((ARM_LPAE_MAX_LEVELS - (l)) * (d)->bits_per_level)))
> +#define ARM_LPAE_BLOCK_SIZE(l,d) (1ULL << ARM_LPAE_LVL_SHIFT(l,d))
>
> /* Page table bits */
> #define ARM_LPAE_PTE_TYPE_SHIFT 0
> @@ -175,8 +174,7 @@ struct arm_lpae_io_pgtable {
>
> int pgd_bits;
> int start_level;
> - unsigned long pg_shift;
> - unsigned long bits_per_level;
> + int bits_per_level;
>
> void *pgd;
> };
> @@ -206,7 +204,7 @@ static phys_addr_t iopte_to_paddr(arm_lpae_iopte pte,
> {
> u64 paddr = pte & ARM_LPAE_PTE_ADDR_MASK;
>
> - if (data->pg_shift < 16)
> + if (data->bits_per_level < 13) /* i.e. 64K granule */
nit, but:
if (ARM_LPAE_GRANULE(data) < SZ_64K)
might be clearer and avoid the need for a comment?
(I can make the change locally if you agree)
Will
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next prev parent reply other threads:[~2019-11-04 18:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 18:08 [PATCH v2 00/10] iommu/io-pgtable: Cleanup and prep for split tables Robin Murphy
2019-10-25 18:08 ` [PATCH v2 01/10] iommu/io-pgtable: Make selftest gubbins consistently __init Robin Murphy
2019-10-25 18:08 ` [PATCH v2 02/10] iommu/io-pgtable-arm: Rationalise size check Robin Murphy
2019-10-25 18:08 ` [PATCH v2 03/10] iommu/io-pgtable-arm: Simplify bounds checks Robin Murphy
2019-10-25 18:08 ` [PATCH v2 04/10] iommu/io-pgtable-arm: Simplify start level lookup Robin Murphy
2019-10-25 18:08 ` [PATCH v2 05/10] iommu/io-pgtable-arm: Simplify PGD size handling Robin Murphy
2019-10-25 18:08 ` [PATCH v2 06/10] iommu/io-pgtable-arm: Simplify level indexing Robin Murphy
2019-11-04 18:17 ` Will Deacon [this message]
2019-11-04 18:36 ` Robin Murphy
2019-11-04 19:20 ` Will Deacon
2019-10-25 18:08 ` [PATCH v2 07/10] iommu/io-pgtable-arm: Rationalise MAIR handling Robin Murphy
2019-11-04 18:20 ` Will Deacon
2019-11-04 18:43 ` Robin Murphy
2019-11-04 19:20 ` Will Deacon
2019-11-04 19:57 ` Will Deacon
2019-10-25 18:08 ` [PATCH v2 08/10] iommu/io-pgtable-arm: Rationalise TTBRn handling Robin Murphy
2019-10-28 15:09 ` Steven Price
2019-10-28 18:51 ` Robin Murphy
2019-11-04 18:36 ` Will Deacon
2019-11-04 19:12 ` Robin Murphy
2019-11-22 22:40 ` Jordan Crouse
2019-10-25 18:08 ` [PATCH v2 09/10] iommu/io-pgtable-arm: Rationalise TCR handling Robin Murphy
2019-11-04 19:14 ` Will Deacon
2019-11-04 23:27 ` Jordan Crouse
[not found] ` <20191120151142.GA26714@willie-the-truck>
2019-11-22 15:51 ` Robin Murphy
2019-11-25 7:58 ` Will Deacon
2019-11-22 22:03 ` Jordan Crouse
2019-10-25 18:08 ` [PATCH v2 10/10] iommu/io-pgtable-arm: Prepare for TTBR1 usage Robin Murphy
2019-11-04 23:40 ` Jordan Crouse
2019-11-20 19:18 ` Will Deacon
2019-11-22 22:03 ` Jordan Crouse
2019-11-04 19:22 ` [PATCH v2 00/10] iommu/io-pgtable: Cleanup and prep for split tables Will Deacon
2019-11-04 20:20 ` Will Deacon
2020-01-10 15:09 ` Will Deacon
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