linux-kernel - [PATCH 3/4] drivers/clocksource/hyper-v: Use TSC PFN getter to map vvar page

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Date:   Tue, 01 Nov 2022 17:31:15 +0000
From:   Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Stanislav Kinsburskiy <stanislav.kinsburskiy@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org
Subject: [PATCH 3/4] drivers/clocksource/hyper-v: Use TSC PFN getter to map
 vvar page

From: Stanislav Kinsburskiy <stanislav.kinsburskiy@...il.com>

Instead of converting the virtual address to physical directly.
This is a precursor patch for the upcoming support for TSC page mapping into
hyper-v root partition, which address will be defined by the hypervisor and
mapped into the kernel.

Signed-off-by: Stanislav Kinsburskiy <stanislav.kinsburskiy@...il.com>
CC: Andy Lutomirski <luto@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...hat.com>
CC: Borislav Petkov <bp@...en8.de>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: x86@...nel.org
CC: "H. Peter Anvin" <hpa@...or.com>
CC: "K. Y. Srinivasan" <kys@...rosoft.com>
CC: Haiyang Zhang <haiyangz@...rosoft.com>
CC: Wei Liu <wei.liu@...nel.org>
CC: Dexuan Cui <decui@...rosoft.com>
CC: Daniel Lezcano <daniel.lezcano@...aro.org>
CC: linux-kernel@...r.kernel.org
CC: linux-hyperv@...r.kernel.org
---
 arch/x86/entry/vdso/vma.c          |    7 +++----
 drivers/clocksource/hyperv_timer.c |    3 ++-
 include/clocksource/hyperv_timer.h |    6 ++++++
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 311eae30e089..6976416b2c9f 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -210,11 +210,10 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 					pgprot_decrypted(vma->vm_page_prot));
 		}
 	} else if (sym_offset == image->sym_hvclock_page) {
-		struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();
+		pfn = hv_get_tsc_pfn();
 
-		if (tsc_pg && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
-			return vmf_insert_pfn(vma, vmf->address,
-					virt_to_phys(tsc_pg) >> PAGE_SHIFT);
+		if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
+			return vmf_insert_pfn(vma, vmf->address, pfn);
 	} else if (sym_offset == image->sym_timens_page) {
 		struct page *timens_page = find_timens_vvar_page(vma);
 
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index d447bc99a399..635c14c1e3bf 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -369,10 +369,11 @@ static union {
 static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
 static unsigned long tsc_pfn;
 
-static unsigned long hv_get_tsc_pfn(void)
+unsigned long hv_get_tsc_pfn(void)
 {
 	return tsc_pfn;
 }
+EXPORT_SYMBOL_GPL(hv_get_tsc_pfn);
 
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index b3f5d73ae1d6..3078d23faaea 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -32,6 +32,7 @@ extern void hv_stimer0_isr(void);
 
 extern void hv_init_clocksource(void);
 
+extern unsigned long hv_get_tsc_pfn(void);
 extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
 
 static inline notrace u64
@@ -90,6 +91,11 @@ hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
 }
 
 #else /* CONFIG_HYPERV_TIMER */
+static inline unsigned long hv_get_tsc_pfn(void)
+{
+	return 0;
+}
+
 static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 {
 	return NULL;