linux-kernel - [PATCH V2 1/2] clocksource/Hyper-v: Allocate Hyper-V tsc page statically

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Date:   Wed, 14 Aug 2019 20:32:15 +0800
From:   lantianyu1986@...il.com
To:     luto@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, sashal@...nel.org,
        daniel.lezcano@...aro.org, arnd@...db.de,
        michael.h.kelley@...rosoft.com
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [PATCH V2 1/2] clocksource/Hyper-v: Allocate Hyper-V tsc page statically

From: Tianyu Lan <Tianyu.Lan@...rosoft.com>

Prepare to add Hyper-V sched clock callback and move Hyper-V
Reference TSC initialization much earlier in the boot process.  Earlier
initialization is needed so that it happens while the timestamp value
is still 0 and no discontinuity in the timestamp will occur when
pv_ops.time.sched_clock calculates its offset.  The earlier
initialization requires that the Hyper-V TSC page be allocated
statically instead of with vmalloc(), so fixup the references
to the TSC page and the method of getting its physical address.

Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
---
    Change since v1:
           - Update commit log
           - Remove and operation of tsc page's va with PAGE_MASK

 arch/x86/entry/vdso/vma.c          |  2 +-
 drivers/clocksource/hyperv_timer.c | 12 ++++--------
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 349a61d8bf34..f5937742b290 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -122,7 +122,7 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 
 		if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
 			return vmf_insert_pfn(vma, vmf->address,
-					vmalloc_to_pfn(tsc_pg));
+					virt_to_phys(tsc_pg) >> PAGE_SHIFT);
 	}
 
 	return VM_FAULT_SIGBUS;
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index ba2c79e6a0ee..432aa331df04 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -214,17 +214,17 @@ EXPORT_SYMBOL_GPL(hyperv_cs);
 
 #ifdef CONFIG_HYPERV_TSCPAGE
 
-static struct ms_hyperv_tsc_page *tsc_pg;
+static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
-	return tsc_pg;
+	return &tsc_pg;
 }
 EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 
 static u64 notrace read_hv_sched_clock_tsc(void)
 {
-	u64 current_tick = hv_read_tsc_page(tsc_pg);
+	u64 current_tick = hv_read_tsc_page(&tsc_pg);
 
 	if (current_tick == U64_MAX)
 		hv_get_time_ref_count(current_tick);
@@ -280,12 +280,8 @@ static bool __init hv_init_tsc_clocksource(void)
 	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
 		return false;
 
-	tsc_pg = vmalloc(PAGE_SIZE);
-	if (!tsc_pg)
-		return false;
-
 	hyperv_cs = &hyperv_cs_tsc;
-	phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
+	phys_addr = virt_to_phys(&tsc_pg);
 
 	/*
 	 * The Hyper-V TLFS specifies to preserve the value of reserved
-- 
2.14.5