Hi Tianyu,
Few comments below.
On Thu, Jan 31, 2019 at 06:17:32PM +0800, lantianyu1...@gmail.com wrote:
From: Lan Tianyu <tianyu....@microsoft.com>
On the bare metal, enabling X2APIC mode requires interrupt remapping
function which helps to deliver irq to cpu with 32-bit APIC ID.
Hyper-V doesn't provide interrupt remapping function so far and Hyper-V
MSI protocol already supports to deliver interrupt to the CPU whose
virtual processor index is more than 255. IO-APIC interrupt still has
8-bit APIC ID limitation.
This patch is to add Hyper-V stub IOMMU driver in order to enable
X2APIC mode successfully in Hyper-V Linux guest. The driver returns X2APIC
interrupt remapping capability when X2APIC mode is available. Otherwise,
it creates a Hyper-V irq domain to limit IO-APIC interrupts' affinity
and make sure cpus assigned with IO-APIC interrupt have 8-bit APIC ID.
Signed-off-by: Lan Tianyu <tianyu....@microsoft.com>
---
drivers/iommu/Kconfig | 7 ++
drivers/iommu/Makefile | 1 +
drivers/iommu/hyperv-iommu.c | 189 ++++++++++++++++++++++++++++++++++++++++++
drivers/iommu/irq_remapping.c | 3 +
drivers/iommu/irq_remapping.h | 1 +
5 files changed, 201 insertions(+)
create mode 100644 drivers/iommu/hyperv-iommu.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 45d7021..5c397c0 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -437,4 +437,11 @@ config QCOM_IOMMU
help
Support for IOMMU on certain Qualcomm SoCs.
+config HYPERV_IOMMU
+ bool "Hyper-V stub IOMMU support"
+ depends on HYPERV
select IOMMU_API ?
+ help
+ Hyper-V stub IOMMU driver provides capability to run
+ Linux guest with X2APIC mode enabled.
+
endif # IOMMU_SUPPORT
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index a158a68..8c71a15 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -32,3 +32,4 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
+obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
new file mode 100644
index 0000000..a64b747
--- /dev/null
+++ b/drivers/iommu/hyperv-iommu.c
@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt) "HYPERV-IR: " fmt
+
+#include <linux/types.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/iommu.h>
+#include <linux/module.h>
+
+#include <asm/hw_irq.h>
+#include <asm/io_apic.h>
+#include <asm/irq_remapping.h>
+#include <asm/hypervisor.h>
+
+#include "irq_remapping.h"
+
+/*
+ * According IO-APIC spec, IO APIC has a 24-entry Interrupt
+ * Redirection Table.
Can the spec be linked somewhere? In the commit message, or here?
+ */
+#define IOAPIC_REMAPPING_ENTRY 24
+
+static cpumask_t ioapic_max_cpumask = { CPU_BITS_NONE };
+struct irq_domain *ioapic_ir_domain;
+
+static int hyperv_ir_set_affinity(struct irq_data *data,
+ const struct cpumask *mask, bool force)
+{
+ struct irq_data *parent = data->parent_data;
+ struct irq_cfg *cfg = irqd_cfg(data);
+ struct IO_APIC_route_entry *entry;
+ cpumask_t cpumask;
+ int ret;
+
+ cpumask_andnot(&cpumask, mask, &ioapic_max_cpumask);
+
+ /* Return error If new irq affinity is out of ioapic_max_cpumask. */
+ if (!cpumask_empty(&cpumask))
+ return -EINVAL;
+
+ ret = parent->chip->irq_set_affinity(parent, mask, force);
+ if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
+ return ret;
+
+ entry = data->chip_data;
+ entry->dest = cfg->dest_apicid;
+ entry->vector = cfg->vector;
+ send_cleanup_vector(cfg);
+
+ return 0;
+}
+
+static struct irq_chip hyperv_ir_chip = {
+ .name = "HYPERV-IR",
+ .irq_ack = apic_ack_irq,
+ .irq_set_affinity = hyperv_ir_set_affinity,
+};
+
+static int hyperv_irq_remapping_alloc(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs,
+ void *arg)
+{
+ struct irq_alloc_info *info = arg;
+ struct IO_APIC_route_entry *entry;
What's the role of this variable? We set it, once, later on in the
function but that's all?
+ struct irq_data *irq_data;
+ struct irq_desc *desc;
+ struct irq_cfg *cfg;
+ int ret = 0;
+
+ if (!info || info->type != X86_IRQ_ALLOC_TYPE_IOAPIC || nr_irqs > 1)
+ return -EINVAL;
+
+ ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, arg);
+ if (ret < 0)
+ goto fail;
+
+ irq_data = irq_domain_get_irq_data(domain, virq);
+ cfg = irqd_cfg(irq_data);
Is this actually being used anywhere, or do we only need it for the
check below? It's not clear from the code why we're calling irqd_cfg()
and ignoring the result.
+ if (!irq_data || !cfg) {
You just dereferenced irq_data in the line above this one, it's a bit
late to check that it's not NULL.
+ ret = -EINVAL;
+ goto fail;
+ }
+
+ irq_data->chip = &hyperv_ir_chip;
+
+ /*
+ * Save IOAPIC entry pointer here in order to set vector and
+ * and dest_apicid in the hyperv_irq_remappng_activate()
+ * and hyperv_ir_set_affinity(). IOAPIC driver ignores
+ * cfg->dest_apicid and cfg->vector when irq remapping
+ * mode is enabled. Detail see ioapic_configure_entry().
+ */
+ irq_data->chip_data = entry = info->ioapic_entry;
+
+ /*
+ * Hypver-V IO APIC irq affinity should be in the scope of
+ * ioapic_max_cpumask because no irq remapping support.
+ */
+ desc = irq_data_to_desc(irq_data);
+ cpumask_and(desc->irq_common_data.affinity,
+ desc->irq_common_data.affinity,
+ &ioapic_max_cpumask);
+
+ fail:
+ return ret;
This one doesn't actually free anything?
+}
+
+static void hyperv_irq_remapping_free(struct irq_domain *domain,
+ unsigned int virq, unsigned int nr_irqs)
+{
+ irq_domain_free_irqs_common(domain, virq, nr_irqs);
+}
+
+static int hyperv_irq_remappng_activate(struct irq_domain *domain,
+ struct irq_data *irq_data, bool reserve)
+{
+ struct irq_cfg *cfg = irqd_cfg(irq_data);
+ struct IO_APIC_route_entry *entry = irq_data->chip_data;
+
+ entry->dest = cfg->dest_apicid;
+ entry->vector = cfg->vector;
+
+ return 0;
+}
+
+static struct irq_domain_ops hyperv_ir_domain_ops = {
+ .alloc = hyperv_irq_remapping_alloc,
+ .free = hyperv_irq_remapping_free,
+ .activate = hyperv_irq_remappng_activate,
+};
+
+static int __init hyperv_prepare_irq_remapping(void)
+{
+ struct fwnode_handle *fn;
+ u32 apic_id;
+ int i;
+
+ if (x86_hyper_type != X86_HYPER_MS_HYPERV ||
+ !x2apic_supported())
+ return -ENODEV;
+
+ fn = irq_domain_alloc_named_id_fwnode("HYPERV-IR", 0);
+ if (!fn)
+ return -EFAULT;
Why EFAULT? The only reason irq_domain_alloc_named_id_fwnode() might
fail is running out of memory.
+
+ ioapic_ir_domain =
+ irq_domain_create_hierarchy(arch_get_ir_parent_domain(),
+ 0, IOAPIC_REMAPPING_ENTRY, fn,
+ &hyperv_ir_domain_ops, NULL);
+
+ irq_domain_free_fwnode(fn);
+
+ /*
+ * Hyper-V doesn't provide irq remapping function for
+ * IO-APIC and so IO-APIC only accepts 8-bit APIC ID.
+ * Prepare max cpu affinity for IOAPIC irqs. Scan cpu 0-255
+ * and set cpu into ioapic_max_cpumask if its APIC ID is less
+ * than 255.
Off-by-one here: it'll set the CPU in the affinity mask if it's less
than 256, not 255.
+ */
+ for (i = 0; i < 256; i++) {
+ apic_id = cpu_physical_id(i);
+ if (apic_id > 255)
+ continue;
+
+ cpumask_set_cpu(i, &ioapic_max_cpumask);
+ }
I'm curious here: assuming we have a large amount of CPUs, what
guarantee do we have that this mask will have anything set? What happens
if it remains empty?
+
+ return 0;
+}
+
+static int __init hyperv_enable_irq_remapping(void)
+{
+ return IRQ_REMAP_X2APIC_MODE;
+}
+
+static struct irq_domain *hyperv_get_ir_irq_domain(struct irq_alloc_info *info)
+{
+ if (info->type == X86_IRQ_ALLOC_TYPE_IOAPIC)
+ return ioapic_ir_domain;
+ else
+ return NULL;
+}
+
+struct irq_remap_ops hyperv_irq_remap_ops = {
+ .prepare = hyperv_prepare_irq_remapping,
+ .enable = hyperv_enable_irq_remapping,
+ .get_ir_irq_domain = hyperv_get_ir_irq_domain,
+};
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index b94ebd4..81cf290 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -103,6 +103,9 @@ int __init irq_remapping_prepare(void)
else if (IS_ENABLED(CONFIG_AMD_IOMMU) &&
amd_iommu_irq_ops.prepare() == 0)
remap_ops = &amd_iommu_irq_ops;
+ else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) &&
+ hyperv_irq_remap_ops.prepare() == 0)
+ remap_ops = &hyperv_irq_remap_ops;
else
return -ENOSYS;
diff --git a/drivers/iommu/irq_remapping.h b/drivers/iommu/irq_remapping.h
index 0afef6e..f8609e9 100644
--- a/drivers/iommu/irq_remapping.h
+++ b/drivers/iommu/irq_remapping.h
@@ -64,6 +64,7 @@ struct irq_remap_ops {
extern struct irq_remap_ops intel_irq_remap_ops;
extern struct irq_remap_ops amd_iommu_irq_ops;
+extern struct irq_remap_ops hyperv_irq_remap_ops;
#else /* CONFIG_IRQ_REMAP */
--
2.7.4
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