From: David Gibson <david@gibson.dropbear.id.au>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: linuxppc-dev@lists.ozlabs.org,
Alex Williamson <alex.williamson@redhat.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Gavin Shan <gwshan@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH kernel v11 09/34] vfio: powerpc/spapr: Move locked_vm accounting to helpers
Date: Mon, 1 Jun 2015 14:28:14 +1000 [thread overview]
Message-ID: <20150601042814.GH22789@voom.redhat.com> (raw)
In-Reply-To: <1432889098-22924-10-git-send-email-aik@ozlabs.ru>
[-- Attachment #1: Type: text/plain, Size: 6106 bytes --]
On Fri, May 29, 2015 at 06:44:33PM +1000, Alexey Kardashevskiy wrote:
> There moves locked pages accounting to helpers.
> Later they will be reused for Dynamic DMA windows (DDW).
>
> This reworks debug messages to show the current value and the limit.
>
> This stores the locked pages number in the container so when unlocking
> the iommu table pointer won't be needed. This does not have an effect
> now but it will with the multiple tables per container as then we will
> allow attaching/detaching groups on fly and we may end up having
> a container with no group attached but with the counter incremented.
>
> While we are here, update the comment explaining why RLIMIT_MEMLOCK
> might be required to be bigger than the guest RAM. This also prints
> pid of the current process in pr_warn/pr_debug.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> [aw: for the vfio related changes]
> Acked-by: Alex Williamson <alex.williamson@redhat.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> ---
> Changes:
> v4:
> * new helpers do nothing if @npages == 0
> * tce_iommu_disable() now can decrement the counter if the group was
> detached (not possible now but will be in the future)
> ---
> drivers/vfio/vfio_iommu_spapr_tce.c | 82 ++++++++++++++++++++++++++++---------
> 1 file changed, 63 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 64300cc..40583f9 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -29,6 +29,51 @@
> static void tce_iommu_detach_group(void *iommu_data,
> struct iommu_group *iommu_group);
>
> +static long try_increment_locked_vm(long npages)
> +{
> + long ret = 0, locked, lock_limit;
> +
> + if (!current || !current->mm)
> + return -ESRCH; /* process exited */
> +
> + if (!npages)
> + return 0;
> +
> + down_write(¤t->mm->mmap_sem);
> + locked = current->mm->locked_vm + npages;
Is there a possibility of userspace triggering an integer overflow
here, if npages is really huge?
> + lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> + if (locked > lock_limit && !capable(CAP_IPC_LOCK))
> + ret = -ENOMEM;
> + else
> + current->mm->locked_vm += npages;
> +
> + pr_debug("[%d] RLIMIT_MEMLOCK +%ld %ld/%ld%s\n", current->pid,
> + npages << PAGE_SHIFT,
> + current->mm->locked_vm << PAGE_SHIFT,
> + rlimit(RLIMIT_MEMLOCK),
> + ret ? " - exceeded" : "");
> +
> + up_write(¤t->mm->mmap_sem);
> +
> + return ret;
> +}
> +
> +static void decrement_locked_vm(long npages)
> +{
> + if (!current || !current->mm || !npages)
> + return; /* process exited */
> +
> + down_write(¤t->mm->mmap_sem);
> + if (npages > current->mm->locked_vm)
> + npages = current->mm->locked_vm;
Can this case ever occur (without there being a leak bug somewhere
else in the code)?
> + current->mm->locked_vm -= npages;
> + pr_debug("[%d] RLIMIT_MEMLOCK -%ld %ld/%ld\n", current->pid,
> + npages << PAGE_SHIFT,
> + current->mm->locked_vm << PAGE_SHIFT,
> + rlimit(RLIMIT_MEMLOCK));
> + up_write(¤t->mm->mmap_sem);
> +}
> +
> /*
> * VFIO IOMMU fd for SPAPR_TCE IOMMU implementation
> *
> @@ -45,6 +90,7 @@ struct tce_container {
> struct mutex lock;
> struct iommu_table *tbl;
> bool enabled;
> + unsigned long locked_pages;
> };
>
> static bool tce_page_is_contained(struct page *page, unsigned page_shift)
> @@ -60,7 +106,7 @@ static bool tce_page_is_contained(struct page *page, unsigned page_shift)
> static int tce_iommu_enable(struct tce_container *container)
> {
> int ret = 0;
> - unsigned long locked, lock_limit, npages;
> + unsigned long locked;
> struct iommu_table *tbl = container->tbl;
>
> if (!container->tbl)
> @@ -89,21 +135,22 @@ static int tce_iommu_enable(struct tce_container *container)
> * Also we don't have a nice way to fail on H_PUT_TCE due to ulimits,
> * that would effectively kill the guest at random points, much better
> * enforcing the limit based on the max that the guest can map.
> + *
> + * Unfortunately at the moment it counts whole tables, no matter how
> + * much memory the guest has. I.e. for 4GB guest and 4 IOMMU groups
> + * each with 2GB DMA window, 8GB will be counted here. The reason for
> + * this is that we cannot tell here the amount of RAM used by the guest
> + * as this information is only available from KVM and VFIO is
> + * KVM agnostic.
> */
> - down_write(¤t->mm->mmap_sem);
> - npages = (tbl->it_size << tbl->it_page_shift) >> PAGE_SHIFT;
> - locked = current->mm->locked_vm + npages;
> - lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> - if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
> - pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
> - rlimit(RLIMIT_MEMLOCK));
> - ret = -ENOMEM;
> - } else {
> + locked = (tbl->it_size << tbl->it_page_shift) >> PAGE_SHIFT;
> + ret = try_increment_locked_vm(locked);
> + if (ret)
> + return ret;
>
> - current->mm->locked_vm += npages;
> - container->enabled = true;
> - }
> - up_write(¤t->mm->mmap_sem);
> + container->locked_pages = locked;
> +
> + container->enabled = true;
>
> return ret;
> }
> @@ -115,13 +162,10 @@ static void tce_iommu_disable(struct tce_container *container)
>
> container->enabled = false;
>
> - if (!container->tbl || !current->mm)
> + if (!current->mm)
> return;
>
> - down_write(¤t->mm->mmap_sem);
> - current->mm->locked_vm -= (container->tbl->it_size <<
> - container->tbl->it_page_shift) >> PAGE_SHIFT;
> - up_write(¤t->mm->mmap_sem);
> + decrement_locked_vm(container->locked_pages);
> }
>
> static void *tce_iommu_open(unsigned long arg)
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2015-06-01 5:47 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-29 8:44 [PATCH kernel v11 00/34] powerpc/iommu/vfio: Enable Dynamic DMA windows Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 01/34] powerpc/eeh/ioda2: Use device::iommu_group to check IOMMU group Alexey Kardashevskiy
2015-06-01 3:40 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 02/34] powerpc/iommu/powernv: Get rid of set_iommu_table_base_and_group Alexey Kardashevskiy
2015-06-01 3:47 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 03/34] powerpc/powernv/ioda: Clean up IOMMU group registration Alexey Kardashevskiy
2015-06-01 3:55 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 04/34] powerpc/iommu: Put IOMMU group explicitly Alexey Kardashevskiy
2015-06-01 3:58 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table() Alexey Kardashevskiy
2015-06-01 4:03 ` David Gibson
2015-06-05 0:10 ` Gavin Shan
2015-05-29 8:44 ` [PATCH kernel v11 06/34] vfio: powerpc/spapr: Move page pinning from arch code to VFIO IOMMU driver Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 07/34] vfio: powerpc/spapr: Check that IOMMU page is fully contained by system page Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 08/34] vfio: powerpc/spapr: Use it_page_size Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 09/34] vfio: powerpc/spapr: Move locked_vm accounting to helpers Alexey Kardashevskiy
2015-06-01 4:28 ` David Gibson [this message]
2015-06-03 11:11 ` Alexey Kardashevskiy
2015-06-04 1:00 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 10/34] vfio: powerpc/spapr: Disable DMA mappings on disabled container Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 11/34] vfio: powerpc/spapr: Moving pinning/unpinning to helpers Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 12/34] vfio: powerpc/spapr: Rework groups attaching Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 13/34] powerpc/powernv: Do not set "read" flag if direction==DMA_NONE Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 14/34] powerpc/iommu: Move tce_xxx callbacks from ppc_md to iommu_table Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 15/34] powerpc/powernv/ioda/ioda2: Rework TCE invalidation in tce_build()/tce_free() Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 16/34] powerpc/spapr: vfio: Replace iommu_table with iommu_table_group Alexey Kardashevskiy
2015-06-01 5:11 ` David Gibson
2015-06-05 0:19 ` Gavin Shan
2015-05-29 8:44 ` [PATCH kernel v11 17/34] powerpc/spapr: vfio: Switch from iommu_table to new iommu_table_group Alexey Kardashevskiy
2015-06-01 6:24 ` David Gibson
2015-06-04 9:14 ` Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 18/34] vfio: powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control Alexey Kardashevskiy
2015-06-01 6:34 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 19/34] powerpc/iommu: Fix IOMMU ownership control functions Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 20/34] powerpc/powernv/ioda2: Move TCE kill register address to PE Alexey Kardashevskiy
2015-06-01 6:47 ` David Gibson
2015-06-05 0:22 ` Gavin Shan
2015-05-29 8:44 ` [PATCH kernel v11 21/34] powerpc/powernv/ioda2: Add TCE invalidation for all attached groups Alexey Kardashevskiy
2015-06-01 6:49 ` David Gibson
2015-06-05 0:27 ` Gavin Shan
2015-06-05 2:54 ` Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 22/34] powerpc/powernv: Implement accessor to TCE entry Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 23/34] powerpc/iommu/powernv: Release replaced TCE Alexey Kardashevskiy
2015-06-01 7:04 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 24/34] powerpc/powernv/ioda2: Rework iommu_table creation Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 25/34] powerpc/powernv/ioda2: Introduce helpers to allocate TCE pages Alexey Kardashevskiy
2015-06-01 7:29 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 26/34] powerpc/powernv/ioda2: Introduce pnv_pci_ioda2_set_window Alexey Kardashevskiy
2015-06-01 23:30 ` David Gibson
2015-06-03 11:18 ` Alexey Kardashevskiy
2015-05-29 8:44 ` [PATCH kernel v11 27/34] powerpc/powernv: Implement multilevel TCE tables Alexey Kardashevskiy
2015-06-01 23:50 ` David Gibson
2015-06-03 11:27 ` Alexey Kardashevskiy
2015-06-04 1:16 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 28/34] vfio: powerpc/spapr: powerpc/powernv/ioda: Define and implement DMA windows API Alexey Kardashevskiy
2015-06-02 0:24 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 29/34] powerpc/powernv/ioda2: Use new helpers to do proper cleanup on PE release Alexey Kardashevskiy
2015-06-02 0:47 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 30/34] powerpc/iommu/ioda2: Add get_table_size() to calculate the size of future table Alexey Kardashevskiy
2015-06-02 0:54 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 31/34] vfio: powerpc/spapr: powerpc/powernv/ioda2: Use DMA windows API in ownership control Alexey Kardashevskiy
2015-06-02 1:09 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 32/34] powerpc/mmu: Add userspace-to-physical addresses translation cache Alexey Kardashevskiy
2015-06-02 1:40 ` David Gibson
2015-05-29 8:44 ` [PATCH kernel v11 33/34] vfio: powerpc/spapr: Register memory and define IOMMU v2 Alexey Kardashevskiy
2015-06-02 4:17 ` David Gibson
2015-06-03 11:40 ` Alexey Kardashevskiy
2015-06-04 1:20 ` David Gibson
2015-06-05 0:01 ` Gavin Shan
2015-05-29 8:44 ` [PATCH kernel v11 34/34] vfio: powerpc/spapr: Support Dynamic DMA windows Alexey Kardashevskiy
2015-06-02 4:37 ` David Gibson
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