From: "Jan Beulich" <JBeulich@suse.com>
To: "Paul Durrant" <paul.durrant@citrix.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Wei Liu <wei.liu2@citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Julien Grall <julien.grall@arm.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Brian Woods <brian.woods@amd.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 3/5] iommu: move iommu_get_ops() into common code
Date: Mon, 13 May 2019 10:11:21 -0600 [thread overview]
Message-ID: <5CD99729020000780022E4B1@prv1-mh.provo.novell.com> (raw)
Message-ID: <20190513161121.RGgnNQ-4UFsJwSqDZIChGoNqRsusfdtzb4xhstDZOlw@z> (raw)
In-Reply-To: <20190508132403.1454-4-paul.durrant@citrix.com>
>>> On 08.05.19 at 15:24, <paul.durrant@citrix.com> wrote:
> Currently x86 and ARM differ in their implementation for no good reason.
> This patch moves the ARM variant of iommu_get/set_ops() helpers into
> common code and modifies them so they deal with the __initconstrel
> ops structures used by the x86 IOMMU vendor implementations (adding
> __initconstrel to the SMMU code to bring it in line). Consequently, a lack
> of init() method is now taken to mean uninitialized iommu_ops. Also, the
> printk warning in iommu_set_ops() now becomes an ASSERT.
When having submitted the indirect call overhead reduction series
including IOMMU changes for the first time, I was told that the Arm
folks would like to retain the ability to eventually support
heterogeneous IOMMUs (and hence I shouldn't provide patching
infrastructure there). A single global iommu_[gs]et_ops() is sort of
getting in the way of this as well, I think, and hence I'm not sure it
is a desirable step to make this so far Arm-specific arrangement
the general model. At least it would further complicate Arm side
changes towards that (mid / long term?) goal.
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -21,6 +21,21 @@
> #include <xen/keyhandler.h>
> #include <xsm/xsm.h>
>
> +static struct iommu_ops __read_mostly iommu_ops;
> +
> +const struct iommu_ops *iommu_get_ops(void)
> +{
> + return &iommu_ops;
> +}
> +
> +void __init iommu_set_ops(const struct iommu_ops *ops)
> +{
> + BUG_ON(!ops);
> +
> + ASSERT(!iommu_ops.init || iommu_ops.init == ops->init);
> + iommu_ops = *ops;
> +}
I realize that you merely move (and slightly re-arrange) what has
been there, but now that I look at it again I think ops->init should
also be verified to be non-NULL, or else installing such a set of
hooks would effectively revert back to the "no hooks yet" state.
> @@ -33,11 +32,7 @@ int __init iommu_hardware_setup(void)
> if ( !iommu_init_ops )
> return -ENODEV;
>
> - if ( !iommu_ops.init )
> - iommu_ops = *iommu_init_ops->ops;
> - else
> - /* x2apic setup may have previously initialised the struct. */
> - ASSERT(iommu_ops.init == iommu_init_ops->ops->init);
> + iommu_set_ops(iommu_init_ops->ops);
I was specifically asked to add the comment that you get rid of.
While mentioning x2APIC in common code may no be appropriate,
I'm sure this could be worded in a more general way and attached
to the moved check.
Jan
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next prev parent reply other threads:[~2019-05-13 16:11 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-08 13:23 [PATCH 0/5] iommu groups + cleanup Paul Durrant
2019-05-08 13:23 ` [Xen-devel] " Paul Durrant
2019-05-08 13:23 ` [PATCH 1/5] iommu: trivial re-organisation to avoid unnecessary test Paul Durrant
2019-05-08 13:23 ` [Xen-devel] " Paul Durrant
2019-05-13 15:22 ` Jan Beulich
2019-05-13 15:22 ` [Xen-devel] " Jan Beulich
2019-05-08 13:24 ` [PATCH 2/5] iommu / x86: move call to scan_pci_devices() out of vendor code Paul Durrant
2019-05-08 13:24 ` [Xen-devel] " Paul Durrant
2019-05-13 15:35 ` Jan Beulich
2019-05-13 15:35 ` [Xen-devel] " Jan Beulich
2019-05-14 16:13 ` Paul Durrant
2019-05-14 16:13 ` [Xen-devel] " Paul Durrant
2019-05-15 6:29 ` Jan Beulich
2019-05-15 6:29 ` [Xen-devel] " Jan Beulich
2019-05-08 13:24 ` [PATCH 3/5] iommu: move iommu_get_ops() into common code Paul Durrant
2019-05-08 13:24 ` [Xen-devel] " Paul Durrant
2019-05-13 16:11 ` Jan Beulich [this message]
2019-05-13 16:11 ` Jan Beulich
2019-05-14 16:19 ` Paul Durrant
2019-05-14 16:19 ` [Xen-devel] " Paul Durrant
2019-05-14 21:36 ` Julien Grall
2019-05-14 21:36 ` [Xen-devel] " Julien Grall
2019-05-15 6:32 ` Jan Beulich
2019-05-15 6:32 ` [Xen-devel] " Jan Beulich
2019-05-08 13:24 ` [PATCH 4/5] iommu: introduce iommu_groups Paul Durrant
2019-05-08 13:24 ` [Xen-devel] " Paul Durrant
2019-05-15 8:44 ` Roger Pau Monné
2019-05-15 8:44 ` [Xen-devel] " Roger Pau Monné
2019-05-31 13:48 ` Paul Durrant
2019-05-31 13:48 ` [Xen-devel] " Paul Durrant
2019-05-15 14:17 ` Jan Beulich
2019-05-15 14:17 ` [Xen-devel] " Jan Beulich
2019-05-31 13:55 ` Paul Durrant
2019-05-31 13:55 ` [Xen-devel] " Paul Durrant
2019-05-31 14:13 ` Jan Beulich
2019-05-31 14:13 ` [Xen-devel] " Jan Beulich
2019-05-31 14:21 ` Paul Durrant
2019-05-31 14:21 ` [Xen-devel] " Paul Durrant
2019-05-15 14:24 ` Jan Beulich
2019-05-15 14:24 ` [Xen-devel] " Jan Beulich
2019-05-08 13:24 ` [PATCH 5/5] iommu / pci: re-implement XEN_DOMCTL_get_device_group Paul Durrant
2019-05-08 13:24 ` [Xen-devel] " Paul Durrant
2019-05-15 9:06 ` Roger Pau Monné
2019-05-15 9:06 ` [Xen-devel] " Roger Pau Monné
2019-06-03 9:58 ` Paul Durrant
2019-06-03 9:58 ` [Xen-devel] " Paul Durrant
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