From: Roman Kagan <rkagan@virtuozzo.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, <x86@kernel.org>,
        Haiyang Zhang <haiyangz@microsoft.com>, <kvm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <devel@linuxdriverproject.org>,
        "Denis V . Lunev" <den@openvz.org>, Roman Kagan <rkagan@virtuozzo.com>
Subject: [PATCH 01/15] hyperv: consolidate TSC ref page definitions
Date: Tue, 20 Dec 2016 18:55:48 +0300
Message-ID: <20161220155602.6298-2-rkagan@virtuozzo.com>
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Consolidate the guest-side and kvm-side definitions for Hyper-V TSC
reference page.

While at this, rewrite read_hv_clock_tsc using the existing helpers.

Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
---
 arch/x86/include/asm/kvm_host.h    |  2 +-
 arch/x86/include/uapi/asm/hyperv.h |  4 +--
 drivers/hv/hyperv_vmbus.h          |  8 ------
 arch/x86/kvm/hyperv.c              |  4 +--
 drivers/hv/hv.c                    | 54 +++++++++++++++-----------------------
 5 files changed, 26 insertions(+), 46 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2e25038..2b85f49 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -713,7 +713,7 @@ struct kvm_hv {
 	u64 hv_crash_param[HV_X64_MSR_CRASH_PARAMS];
 	u64 hv_crash_ctl;
 
-	HV_REFERENCE_TSC_PAGE tsc_ref;
+	struct hv_ref_tsc_page tsc_ref;
 };
 
 struct kvm_arch {
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 9b1a918..6098ab5 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -252,12 +252,12 @@
 #define HV_STATUS_INVALID_CONNECTION_ID		18
 #define HV_STATUS_INSUFFICIENT_BUFFERS		19
 
-typedef struct _HV_REFERENCE_TSC_PAGE {
+struct hv_ref_tsc_page {
 	__u32 tsc_sequence;
 	__u32 res1;
 	__u64 tsc_scale;
 	__s64 tsc_offset;
-} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
+};
 
 /* Define the number of synthetic interrupt sources. */
 #define HV_SYNIC_SINT_COUNT		(16)
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 0675b39..4516498 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -475,14 +475,6 @@ struct hv_context {
 
 extern struct hv_context hv_context;
 
-struct ms_hyperv_tsc_page {
-	volatile u32 tsc_sequence;
-	u32 reserved1;
-	volatile u64 tsc_scale;
-	volatile s64 tsc_offset;
-	u64 reserved2[509];
-};
-
 struct hv_ring_buffer_debug_info {
 	u32 current_interrupt_mask;
 	u32 current_read_index;
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 1572c35..c7db112 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -806,7 +806,7 @@ static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
  * These two equivalencies are implemented in this function.
  */
 static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info *hv_clock,
-					HV_REFERENCE_TSC_PAGE *tsc_ref)
+					struct hv_ref_tsc_page *tsc_ref)
 {
 	u64 max_mul;
 
@@ -847,7 +847,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm,
 	u64 gfn;
 
 	BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv->tsc_ref.tsc_sequence));
-	BUILD_BUG_ON(offsetof(HV_REFERENCE_TSC_PAGE, tsc_sequence) != 0);
+	BUILD_BUG_ON(offsetof(struct hv_ref_tsc_page, tsc_sequence) != 0);
 
 	if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))
 		return;
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 446802a..a7256ec 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -137,41 +137,29 @@ EXPORT_SYMBOL_GPL(hv_do_hypercall);
 #ifdef CONFIG_X86_64
 static cycle_t read_hv_clock_tsc(struct clocksource *arg)
 {
-	cycle_t current_tick;
-	struct ms_hyperv_tsc_page *tsc_pg = hv_context.tsc_page;
+	struct hv_ref_tsc_page *tsc_pg = hv_context.tsc_page;
+	u32 sequence;
+	u64 scale;
+	s64 offset;
+
+	do {
+		sequence = tsc_pg->tsc_sequence;
+		virt_rmb();
+
+		if (!sequence) {
+			/* fallback to MSR */
+			cycle_t current_tick;
+			rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+			return current_tick;
+		}
 
-	if (tsc_pg->tsc_sequence != 0) {
-		/*
-		 * Use the tsc page to compute the value.
-		 */
+		scale = tsc_pg->tsc_scale;
+		offset = tsc_pg->tsc_offset;
 
-		while (1) {
-			cycle_t tmp;
-			u32 sequence = tsc_pg->tsc_sequence;
-			u64 cur_tsc;
-			u64 scale = tsc_pg->tsc_scale;
-			s64 offset = tsc_pg->tsc_offset;
-
-			rdtscll(cur_tsc);
-			/* current_tick = ((cur_tsc *scale) >> 64) + offset */
-			asm("mulq %3"
-				: "=d" (current_tick), "=a" (tmp)
-				: "a" (cur_tsc), "r" (scale));
-
-			current_tick += offset;
-			if (tsc_pg->tsc_sequence == sequence)
-				return current_tick;
-
-			if (tsc_pg->tsc_sequence != 0)
-				continue;
-			/*
-			 * Fallback using MSR method.
-			 */
-			break;
-		}
-	}
-	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-	return current_tick;
+		virt_rmb();
+	} while (tsc_pg->tsc_sequence != sequence);
+
+	return mul_u64_u64_shr(rdtsc_ordered(), scale, 64) + offset;
 }
 
 static struct clocksource hyperv_cs_tsc = {
-- 
2.9.3