Drivers: hv: Move add_interrupt_randomness() to hypervisor callback sysvec

The Hyper-V ISRs, for normal guests and when running in the hypervisor root
patition, are calling add_interrupt_randomness() as a primary source of
entropy. The call is currently in the ISRs as a common place to handle both
x86/x64 and arm64.

On x86/x64, hypervisor interrupts come through a custom sysvec entry, and
do not go through a generic interrupt handler.

On arm64, hypervisor interrupts come through an emulated GICv3. GICv3 uses
the generic handler handle_percpu_devid_irq(), which does not do
add_interrupt_randomness() -- unlike its counterpart
handle_percpu_irq().

But handle_percpu_devid_irq() is now updated to do the
add_interrupt_randomness(). So add_interrupt_randomness() is now needed
only in Hyper-V's x86/x64 custom sysvec path.

Move add_interrupt_randomness() from the Hyper-V ISRs into the Hyper-V
x86/x64 custom sysvec path, matching the existing STIMER0 sysvec path.

With this change, add_interrupt_randomness() is no longer called from any
device drivers, which is appropriate.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: Wei Liu <wei.liu@kernel.org>
Link: https://patch.msgid.link/20260402202400.1707-3-mhklkml@zohomail.com

arch/x86/kernel/cpu/mshyperv.c

@@ -161,6 +161,8 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
 	if (vmbus_handler)
 		vmbus_handler();
 
+	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR);
+
 	if (ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED)
 		apic_eoi();
 

drivers/hv/mshv_synic.c

@@ -12,7 +12,6 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
-#include <linux/random.h>
 #include <linux/cpuhotplug.h>
 #include <linux/reboot.h>
 #include <asm/mshyperv.h>
@@ -445,8 +444,6 @@ void mshv_isr(void)
 		mb();
 		if (msg->header.message_flags.msg_pending)
 			hv_set_non_nested_msr(HV_MSR_EOM, 0);
-
-		add_interrupt_randomness(mshv_sint_vector);
 	} else {
 		pr_warn_once("%s: unknown message type 0x%x\n", __func__,
 			     msg->header.message_type);

drivers/hv/vmbus_drv.c

@@ -32,7 +32,6 @@
 #include <linux/ptrace.h>
 #include <linux/sysfb.h>
 #include <linux/efi.h>
-#include <linux/random.h>
 #include <linux/kernel.h>
 #include <linux/syscore_ops.h>
 #include <linux/dma-map-ops.h>
@@ -1361,8 +1360,6 @@ static void __vmbus_isr(void)
 
 	vmbus_message_sched(hv_cpu, hv_cpu->hyp_synic_message_page);
 	vmbus_message_sched(hv_cpu, hv_cpu->para_synic_message_page);
-
-	add_interrupt_randomness(vmbus_interrupt);
 }
 
 static DEFINE_PER_CPU(bool, vmbus_irq_pending);