On Thu, Feb 04, 2021 at 05:43:16PM +0000, Michael Kelley wrote:
[...]

quoted

quoted

 remove_cpuhp_state:

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
new file mode 100644
index 000000000000..117f17e8c88a
--- /dev/null
+++ b/arch/x86/hyperv/irqdomain.c

@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * for Linux to run as the root partition on Microsoft Hypervisor.

Nit:  Looks like the initial word "Irqdomain" got dropped from the above
comment line.  But don't respin just for this.

I've added it back. Thanks.

quoted

quoted

+static int hv_map_interrupt(union hv_device_id device_id, bool level,
+		int cpu, int vector, struct hv_interrupt_entry *entry)
+{
+	struct hv_input_map_device_interrupt *input;
+	struct hv_output_map_device_interrupt *output;
+	struct hv_device_interrupt_descriptor *intr_desc;
+	unsigned long flags;
+	u64 status;
+	cpumask_t mask = CPU_MASK_NONE;
+	int nr_bank, var_size;
+
+	local_irq_save(flags);
+
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
+
+	intr_desc = &input->interrupt_descriptor;
+	memset(input, 0, sizeof(*input));
+	input->partition_id = hv_current_partition_id;
+	input->device_id = device_id.as_uint64;
+	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
+	intr_desc->vector_count = 1;
+	intr_desc->target.vector = vector;
+
+	if (level)
+		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_LEVEL;
+	else
+		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;
+
+	cpumask_set_cpu(cpu, &mask);
+	intr_desc->target.vp_set.valid_bank_mask = 0;
+	intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
+	nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), &mask);

There's a function get_cpu_mask() that returns a pointer to a cpumask with only
the specified cpu set in the mask.  It returns a const pointer to the correct entry
in a pre-allocated array of all such cpumasks, so it's a lot more efficient than
allocating and initializing a local cpumask instance on the stack.

That's nice.

I've got the following diff to fix both issues. If you're happy with the
changes, can you give your Reviewed-by? That saves a round of posting.

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
index 0cabc9aece38..fa71db798465 100644
--- a/arch/x86/hyperv/irqdomain.c
+++ b/arch/x86/hyperv/irqdomain.c

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0

 /*
- * for Linux to run as the root partition on Microsoft Hypervisor.
+ * Irqdomain for Linux to run as the root partition on Microsoft Hypervisor.
  *
  * Authors:
  *  Sunil Muthuswamy <sunilmut@microsoft.com>

@@ -20,7 +20,7 @@ static int hv_map_interrupt(union hv_device_id device_id, bool level,
        struct hv_device_interrupt_descriptor *intr_desc;
        unsigned long flags;
        u64 status;
-       cpumask_t mask = CPU_MASK_NONE;
+       const cpumask_t *mask;
        int nr_bank, var_size;

        local_irq_save(flags);

@@ -41,10 +41,10 @@ static int hv_map_interrupt(union hv_device_id device_id, bool

level,
        else
                intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;

-       cpumask_set_cpu(cpu, &mask);
+       mask = cpumask_of(cpu);
        intr_desc->target.vp_set.valid_bank_mask = 0;
        intr_desc->target.vp_set.format = HV_GENERIC_SET_SPARSE_4K;
-       nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), &mask);
+       nr_bank = cpumask_to_vpset(&(intr_desc->target.vp_set), mask);