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Date: Thu, 06 Aug 2015 13:20:09 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Joerg Roedel <joro@...tes.org>
Cc: iommu@...ts.linux-foundation.org,
David Woodhouse <dwmw2@...radead.org>,
linux-kernel@...r.kernel.org, jroedel@...e.de
Subject: Re: [PATCH 03/26] iommu/vt-d: Split up iommu->domains array
On Wed, 2015-08-05 at 17:18 +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
>
> This array is indexed by the domain-id and contains the
> pointers to the domains attached to this iommu. Modern
> systems support 65536 domain ids, so that this array has a
> size of 512kb, per iommu.
>
> This is a huge waste of space, as the array is usually
> sparsely populated. This patch makes the array
> two-dimensional and allocates the memory for the domain
> pointers on-demand.
>
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
> drivers/iommu/intel-iommu.c | 54 ++++++++++++++++++++++++++++++++++++---------
> include/linux/intel-iommu.h | 2 +-
> 2 files changed, 44 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index e6a5966..7f2e6c8 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -569,13 +569,32 @@ static struct kmem_cache *iommu_devinfo_cache;
>
> static struct dmar_domain* get_iommu_domain(struct intel_iommu *iommu, u16 did)
> {
> - return iommu->domains[did];
> + struct dmar_domain **domains;
> + int idx = did >> 8;
> +
> + domains = iommu->domains[idx];
> + if (!domains)
> + return NULL;
> +
> + return domains[did & 0xff];
> }
>
> static void set_iommu_domain(struct intel_iommu *iommu, u16 did,
> struct dmar_domain *domain)
> {
> - iommu->domains[did] = domain;
> + struct dmar_domain **domains;
> + int idx = did >> 8;
> +
> + if (!iommu->domains[idx]) {
> + size_t size = 256 * sizeof(struct dmar_domain *);
> + iommu->domains[idx] = kzalloc(size, GFP_ATOMIC);
> + }
> +
> + domains = iommu->domains[idx];
> + if (WARN_ON(!domains))
> + return;
> + else
> + domains[did & 0xff] = domain;
> }
I'm tempted to suggest using pages here since we're dealing with 2k
second level arrays, but maybe caring about pointers per page just makes
that ugly.
>
> static inline void *alloc_pgtable_page(int node)
> @@ -1528,35 +1547,43 @@ static void iommu_disable_translation(struct intel_iommu *iommu)
>
> static int iommu_init_domains(struct intel_iommu *iommu)
> {
> - unsigned long ndomains;
> - unsigned long nlongs;
> + u32 ndomains, nlongs;
> + size_t size;
>
> ndomains = cap_ndoms(iommu->cap);
> - pr_debug("%s: Number of Domains supported <%ld>\n",
> + pr_debug("%s: Number of Domains supported <%d>\n",
> iommu->name, ndomains);
> nlongs = BITS_TO_LONGS(ndomains);
>
> spin_lock_init(&iommu->lock);
>
> - /* TBD: there might be 64K domains,
> - * consider other allocation for future chip
> - */
> iommu->domain_ids = kcalloc(nlongs, sizeof(unsigned long), GFP_KERNEL);
> if (!iommu->domain_ids) {
> pr_err("%s: Allocating domain id array failed\n",
> iommu->name);
> return -ENOMEM;
> }
> - iommu->domains = kcalloc(ndomains, sizeof(struct dmar_domain *),
> - GFP_KERNEL);
> - if (!iommu->domains) {
> +
> + size = ((ndomains >> 8) + 1) * sizeof(struct dmar_domain **);
> + iommu->domains = kzalloc(size, GFP_KERNEL);
> +
> + if (iommu->domains) {
> + size = 256 * sizeof(struct dmar_domain *);
> + iommu->domains[0] = kzalloc(size, GFP_KERNEL);
> + }
> +
> + if (!iommu->domains || !iommu->domains[0]) {
> pr_err("%s: Allocating domain array failed\n",
> iommu->name);
> kfree(iommu->domain_ids);
> + kfree(iommu->domains);
> iommu->domain_ids = NULL;
> + iommu->domains = NULL;
> return -ENOMEM;
> }
>
> +
> +
> /*
> * If Caching mode is set, then invalid translations are tagged
> * with domain-id 0, hence we need to pre-allocate it. We also
> @@ -1598,6 +1625,11 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
> static void free_dmar_iommu(struct intel_iommu *iommu)
> {
> if ((iommu->domains) && (iommu->domain_ids)) {
> + int elems = (cap_ndoms(iommu->cap) >> 8) + 1;
> + int i;
> +
> + for (i = 0; i < elems; i++)
> + kfree(iommu->domains[i]);
> kfree(iommu->domains);
> kfree(iommu->domain_ids);
> iommu->domains = NULL;
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index d9a366d..6240063 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -344,7 +344,7 @@ struct intel_iommu {
>
> #ifdef CONFIG_INTEL_IOMMU
> unsigned long *domain_ids; /* bitmap of domains */
> - struct dmar_domain **domains; /* ptr to domains */
> + struct dmar_domain ***domains; /* ptr to domains */
> spinlock_t lock; /* protect context, domain ids */
> struct root_entry *root_entry; /* virtual address */
>
--
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