From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Leonardo Bras <leobras.c@gmail.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Christophe Leroy <christophe.leroy@c-s.fr>,
Joel Stanley <joel@jms.id.au>,
brking@linux.vnet.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes present in LoPAR
Date: Tue, 23 Mar 2021 18:41:09 +1100 [thread overview]
Message-ID: <2088f84c-08fb-fecc-f5d4-5735357dc296@ozlabs.ru> (raw)
In-Reply-To: <20210322190943.715368-1-leobras.c@gmail.com>
On 23/03/2021 06:09, Leonardo Bras wrote:
> According to LoPAR, ibm,query-pe-dma-window output named "IO Page Sizes"
> will let the OS know all possible pagesizes that can be used for creating a
> new DDW.
>
> Currently Linux will only try using 3 of the 8 available options:
> 4K, 64K and 16M. According to LoPAR, Hypervisor may also offer 32M, 64M,
> 128M, 256M and 16G.
>
> Enabling bigger pages would be interesting for direct mapping systems
> with a lot of RAM, while using less TCE entries.
> > Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
> ---
> arch/powerpc/include/asm/iommu.h | 8 ++++++++
> arch/powerpc/platforms/pseries/iommu.c | 28 +++++++++++++++++++-------
> 2 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index deef7c94d7b6..c170048b7a1b 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -19,6 +19,14 @@
> #include <asm/pci-bridge.h>
> #include <asm/asm-const.h>
>
> +#define IOMMU_PAGE_SHIFT_16G 34
> +#define IOMMU_PAGE_SHIFT_256M 28
> +#define IOMMU_PAGE_SHIFT_128M 27
> +#define IOMMU_PAGE_SHIFT_64M 26
> +#define IOMMU_PAGE_SHIFT_32M 25
> +#define IOMMU_PAGE_SHIFT_16M 24
> +#define IOMMU_PAGE_SHIFT_64K 16
These are not very descriptive, these are just normal shifts, could be
as simple as __builtin_ctz(SZ_4K) (gcc will optimize this) and so on.
OTOH the PAPR page sizes need macros as they are the ones which are
weird and screaming for macros.
I'd steal/rework spapr_page_mask_to_query_mask() from QEMU. Thanks,
> +
> #define IOMMU_PAGE_SHIFT_4K 12
> #define IOMMU_PAGE_SIZE_4K (ASM_CONST(1) << IOMMU_PAGE_SHIFT_4K)
> #define IOMMU_PAGE_MASK_4K (~((1 << IOMMU_PAGE_SHIFT_4K) - 1))
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index 9fc5217f0c8e..02958e80aa91 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -1099,6 +1099,24 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
> ret);
> }
>
> +/* Returns page shift based on "IO Page Sizes" output at ibm,query-pe-dma-window. SeeL LoPAR */
> +static int iommu_get_page_shift(u32 query_page_size)
> +{
> + const int shift[] = {IOMMU_PAGE_SHIFT_4K, IOMMU_PAGE_SHIFT_64K, IOMMU_PAGE_SHIFT_16M,
> + IOMMU_PAGE_SHIFT_32M, IOMMU_PAGE_SHIFT_64M, IOMMU_PAGE_SHIFT_128M,
> + IOMMU_PAGE_SHIFT_256M, IOMMU_PAGE_SHIFT_16G};
> + int i = ARRAY_SIZE(shift) - 1;
> +
> + /* Looks for the largest page size supported */
> + for (; i >= 0; i--) {
> + if (query_page_size & (1 << i))
> + return shift[i];
> + }
> +
> + /* No valid page size found. */
> + return 0;
> +}
> +
> /*
> * If the PE supports dynamic dma windows, and there is space for a table
> * that can map all pages in a linear offset, then setup such a table,
> @@ -1206,13 +1224,9 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
> goto out_failed;
> }
> }
> - if (query.page_size & 4) {
> - page_shift = 24; /* 16MB */
> - } else if (query.page_size & 2) {
> - page_shift = 16; /* 64kB */
> - } else if (query.page_size & 1) {
> - page_shift = 12; /* 4kB */
> - } else {
> +
> + page_shift = iommu_get_page_shift(query.page_size);
> + if (!page_shift) {
> dev_dbg(&dev->dev, "no supported direct page size in mask %x",
> query.page_size);
> goto out_failed;
>
--
Alexey
next prev parent reply other threads:[~2021-03-23 7:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 19:09 [PATCH 1/1] powerpc/iommu: Enable remaining IOMMU Pagesizes present in LoPAR Leonardo Bras
2021-03-23 7:41 ` Alexey Kardashevskiy [this message]
2021-04-07 19:58 ` Leonardo Bras
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