linux-kernel - [PATCH v2 09/15] Drivers: hv: Introduce hv_output_arg_exists in hv

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Message-Id: <1692309711-5573-10-git-send-email-nunodasneves@linux.microsoft.com>
Date:   Thu, 17 Aug 2023 15:01:45 -0700
From:   Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arch@...r.kernel.org
Cc:     patches@...ts.linux.dev, mikelley@...rosoft.com, kys@...rosoft.com,
        wei.liu@...nel.org, haiyangz@...rosoft.com, decui@...rosoft.com,
        apais@...ux.microsoft.com, Tianyu.Lan@...rosoft.com,
        ssengar@...ux.microsoft.com, mukeshrathor@...rosoft.com,
        stanislav.kinsburskiy@...il.com, jinankjain@...ux.microsoft.com,
        vkuznets@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        will@...nel.org, catalin.marinas@....com
Subject: [PATCH v2 09/15] Drivers: hv: Introduce hv_output_arg_exists in hv_common.c

This is a more flexible approach for determining whether to allocate the
output page.

Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
---
 drivers/hv/hv_common.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 0dd3091beef3..79efedc8bf39 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -57,6 +57,14 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
 void * __percpu *hyperv_pcpu_output_arg;
 EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
 
+/*
+ * Determine whether output arg is needed
+ */
+static inline bool hv_output_arg_exists(void)
+{
+	return hv_root_partition ? true : false;
+}
+
 static void hv_kmsg_dump_unregister(void);
 
 static struct ctl_table_header *hv_ctl_table_hdr;
@@ -341,10 +349,12 @@ int __init hv_common_init(void)
 	hyperv_pcpu_input_arg = alloc_percpu(void  *);
 	BUG_ON(!hyperv_pcpu_input_arg);
 
-	/* Allocate the per-CPU state for output arg for root */
-	if (hv_root_partition) {
+	if (hv_output_arg_exists()) {
 		hyperv_pcpu_output_arg = alloc_percpu(void *);
 		BUG_ON(!hyperv_pcpu_output_arg);
+	}
+
+	if (hv_root_partition) {
 		hv_synic_eventring_tail = alloc_percpu(u8 *);
 		BUG_ON(hv_synic_eventring_tail == NULL);
 	}
@@ -374,7 +384,7 @@ int hv_common_cpu_init(unsigned int cpu)
 	u8 **synic_eventring_tail;
 	u64 msr_vp_index;
 	gfp_t flags;
-	int pgcount = hv_root_partition ? 2 : 1;
+	int pgcount = hv_output_arg_exists() ? 2 : 1;
 
 	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
 	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
@@ -390,9 +400,11 @@ int hv_common_cpu_init(unsigned int cpu)
 		if (!(*inputarg))
 			return -ENOMEM;
 
-		if (hv_root_partition) {
+		if (hv_output_arg_exists()) {
 			outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
 			*outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
+		}
+		if (hv_root_partition) {
 			synic_eventring_tail = (u8 **)this_cpu_ptr(hv_synic_eventring_tail);
 			*synic_eventring_tail = kcalloc(HV_SYNIC_SINT_COUNT, sizeof(u8),
 							flags);
-- 
2.25.1