[PATCH 1/2] x86/hyperv: Add callback filter to cpumask_to_vpset()

From: Michael Kelley
Date: Mon Mar 27 2023 - 09:17:28 EST


When copying CPUs from a Linux cpumask to a Hyper-V VPset,
cpumask_to_vpset() currently has a "_noself" variant that doesn't copy
the current CPU to the VPset. Generalize this variant by replacing it
with a "_skip" variant having a callback function that is invoked for
each CPU to decide if that CPU should be copied. Update the one caller
of cpumask_to_vpset_noself() to use the new "_skip" variant instead.

No functional change.

Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
arch/x86/hyperv/hv_apic.c | 12 ++++++++----
include/asm-generic/mshyperv.h | 22 ++++++++++++++--------
2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
index fb8b2c0..1fbda2f 100644
--- a/arch/x86/hyperv/hv_apic.c
+++ b/arch/x86/hyperv/hv_apic.c
@@ -96,6 +96,11 @@ static void hv_apic_eoi_write(u32 reg, u32 val)
wrmsr(HV_X64_MSR_EOI, val, 0);
}

+static bool cpu_is_self(int cpu)
+{
+ return cpu == smp_processor_id();
+}
+
/*
* IPI implementation on Hyper-V.
*/
@@ -128,10 +133,9 @@ static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector,
*/
if (!cpumask_equal(mask, cpu_present_mask) || exclude_self) {
ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K;
- if (exclude_self)
- nr_bank = cpumask_to_vpset_noself(&(ipi_arg->vp_set), mask);
- else
- nr_bank = cpumask_to_vpset(&(ipi_arg->vp_set), mask);
+
+ nr_bank = cpumask_to_vpset_skip(&(ipi_arg->vp_set), mask,
+ exclude_self ? cpu_is_self : NULL);

/*
* 'nr_bank <= 0' means some CPUs in cpumask can't be
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index afcd9ae..402a8c1 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -210,10 +210,9 @@ static inline int hv_cpu_number_to_vp_number(int cpu_number)

static inline int __cpumask_to_vpset(struct hv_vpset *vpset,
const struct cpumask *cpus,
- bool exclude_self)
+ bool (*func)(int cpu))
{
int cpu, vcpu, vcpu_bank, vcpu_offset, nr_bank = 1;
- int this_cpu = smp_processor_id();
int max_vcpu_bank = hv_max_vp_index / HV_VCPUS_PER_SPARSE_BANK;

/* vpset.valid_bank_mask can represent up to HV_MAX_SPARSE_VCPU_BANKS banks */
@@ -232,7 +231,7 @@ static inline int __cpumask_to_vpset(struct hv_vpset *vpset,
* Some banks may end up being empty but this is acceptable.
*/
for_each_cpu(cpu, cpus) {
- if (exclude_self && cpu == this_cpu)
+ if (func && func(cpu))
continue;
vcpu = hv_cpu_number_to_vp_number(cpu);
if (vcpu == VP_INVAL)
@@ -248,17 +247,24 @@ static inline int __cpumask_to_vpset(struct hv_vpset *vpset,
return nr_bank;
}

+/*
+ * Convert a Linux cpumask into a Hyper-V VPset. In the _skip variant,
+ * 'func' is called for each CPU present in cpumask. If 'func' returns
+ * true, that CPU is skipped -- i.e., that CPU from cpumask is *not*
+ * added to the Hyper-V VPset. If 'func' is NULL, no CPUs are
+ * skipped.
+ */
static inline int cpumask_to_vpset(struct hv_vpset *vpset,
const struct cpumask *cpus)
{
- return __cpumask_to_vpset(vpset, cpus, false);
+ return __cpumask_to_vpset(vpset, cpus, NULL);
}

-static inline int cpumask_to_vpset_noself(struct hv_vpset *vpset,
- const struct cpumask *cpus)
+static inline int cpumask_to_vpset_skip(struct hv_vpset *vpset,
+ const struct cpumask *cpus,
+ bool (*func)(int cpu))
{
- WARN_ON_ONCE(preemptible());
- return __cpumask_to_vpset(vpset, cpus, true);
+ return __cpumask_to_vpset(vpset, cpus, func);
}

void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
--
1.8.3.1