Date:   Wed, 21 Dec 2016 18:58:38 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Roman Kagan <rkagan@...tuozzo.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Haiyang Zhang" <haiyangz@...rosoft.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "Denis V . Lunev" <den@...nvz.org>
Subject: RE: [PATCH 02/15] hyperv: uapi-fy synic event flags definitions



> -----Original Message-----
> From: Roman Kagan [mailto:rkagan@...tuozzo.com]
> Sent: Tuesday, December 20, 2016 7:56 AM
> To: Paolo Bonzini <pbonzini@...hat.com>; Radim Krčmář
> <rkrcmar@...hat.com>; KY Srinivasan <kys@...rosoft.com>; Vitaly
> Kuznetsov <vkuznets@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar
> <mingo@...hat.com>; H. Peter Anvin <hpa@...or.com>; x86@...nel.org;
> Haiyang Zhang <haiyangz@...rosoft.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; devel@...uxdriverproject.org; Denis V . Lunev
> <den@...nvz.org>; Roman Kagan <rkagan@...tuozzo.com>
> Subject: [PATCH 02/15] hyperv: uapi-fy synic event flags definitions
> 
> Move definitions related to the Hyper-V SynIC event flags to a header
> where they can be consumed by userspace.
> 
> While doing so, also clean up their use by switching to standard bitops
> and struct-based dereferencing.  The latter is also done for message
> pages.

Please breakup this patch.
> 
> Signed-off-by: Roman Kagan <rkagan@...tuozzo.com>
> ---
>  arch/x86/include/uapi/asm/hyperv.h | 13 +++++++++
>  drivers/hv/hyperv_vmbus.h          | 24 ++--------------
>  drivers/hv/channel_mgmt.c          | 10 +++----
>  drivers/hv/connection.c            | 47 ++++++++++---------------------
>  drivers/hv/vmbus_drv.c             | 57 ++++++++++++++------------------------
>  5 files changed, 54 insertions(+), 97 deletions(-)
> 
> diff --git a/arch/x86/include/uapi/asm/hyperv.h
> b/arch/x86/include/uapi/asm/hyperv.h
> index 6098ab5..af542a3 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -363,4 +363,17 @@ struct hv_timer_message_payload {
>  #define HV_STIMER_AUTOENABLE		(1ULL << 3)
>  #define HV_STIMER_SINT(config)		(__u8)(((config) >> 16) &
> 0x0F)
> 
> +/* Define synthetic interrupt controller flag constants. */
> +#define HV_EVENT_FLAGS_COUNT		(256 * 8)
> +
> +/* Define the synthetic interrupt controller event flags format. */
> +struct hv_synic_event_flags {
> +	__u64 flags[HV_EVENT_FLAGS_COUNT / 64];
> +};
> +
> +/* Define the synthetic interrupt flags page layout. */
> +struct hv_synic_event_flags_page {
> +	struct hv_synic_event_flags
> sintevent_flags[HV_SYNIC_SINT_COUNT];
> +};
> +
>  #endif
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 4516498..4fab154 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -26,7 +26,6 @@
>  #define _HYPERV_VMBUS_H
> 
>  #include <linux/list.h>
> -#include <asm/sync_bitops.h>
>  #include <linux/atomic.h>
>  #include <linux/hyperv.h>
> 
> @@ -75,11 +74,6 @@ enum hv_cpuid_function {
> 
>  #define HV_ANY_VP			(0xFFFFFFFF)
> 
> -/* Define synthetic interrupt controller flag constants. */
> -#define HV_EVENT_FLAGS_COUNT		(256 * 8)
> -#define HV_EVENT_FLAGS_BYTE_COUNT	(256)
> -#define HV_EVENT_FLAGS_DWORD_COUNT	(256 / sizeof(u32))
> -
>  /* Define invalid partition identifier. */
>  #define HV_PARTITION_ID_INVALID		((u64)0x0)
> 
> @@ -146,20 +140,6 @@ union hv_timer_config {
>  	};
>  };
> 
> -/* Define the number of message buffers associated with each port. */
> -#define HV_PORT_MESSAGE_BUFFER_COUNT	(16)
> -
> -/* Define the synthetic interrupt controller event flags format. */
> -union hv_synic_event_flags {
> -	u8 flags8[HV_EVENT_FLAGS_BYTE_COUNT];
> -	u32 flags32[HV_EVENT_FLAGS_DWORD_COUNT];
> -};
> -
> -/* Define the synthetic interrupt flags page layout. */
> -struct hv_synic_event_flags_page {
> -	union hv_synic_event_flags
> sintevent_flags[HV_SYNIC_SINT_COUNT];
> -};
> -
>  /* Define SynIC control register. */
>  union hv_synic_scontrol {
>  	u64 as_uint64;
> @@ -434,8 +414,8 @@ struct hv_context {
> 
>  	bool synic_initialized;
> 
> -	void *synic_message_page[NR_CPUS];
> -	void *synic_event_page[NR_CPUS];
> +	struct hv_message_page *synic_message_page[NR_CPUS];
> +	struct hv_synic_event_flags_page *synic_event_page[NR_CPUS];
>  	/*
>  	 * Hypervisor's notion of virtual processor ID is different from
>  	 * Linux' notion of CPU ID. This information can only be retrieved
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 26b4192..49eaae2 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -654,7 +654,6 @@ static void init_vp_index(struct vmbus_channel
> *channel, u16 dev_type)
>  static void vmbus_wait_for_unload(void)
>  {
>  	int cpu;
> -	void *page_addr;
>  	struct hv_message *msg;
>  	struct vmbus_channel_message_header *hdr;
>  	u32 message_type;
> @@ -673,9 +672,8 @@ static void vmbus_wait_for_unload(void)
>  			break;
> 
>  		for_each_online_cpu(cpu) {
> -			page_addr = hv_context.synic_message_page[cpu];
> -			msg = (struct hv_message *)page_addr +
> -				VMBUS_MESSAGE_SINT;
> +			msg = &hv_context.synic_message_page[cpu]->
> +
> 	sint_message[VMBUS_MESSAGE_SINT];
> 
>  			message_type = READ_ONCE(msg-
> >header.message_type);
>  			if (message_type == HVMSG_NONE)
> @@ -699,8 +697,8 @@ static void vmbus_wait_for_unload(void)
>  	 * messages after we reconnect.
>  	 */
>  	for_each_online_cpu(cpu) {
> -		page_addr = hv_context.synic_message_page[cpu];
> -		msg = (struct hv_message *)page_addr +
> VMBUS_MESSAGE_SINT;
> +		msg = &hv_context.synic_message_page[cpu]->
> +				sint_message[VMBUS_MESSAGE_SINT];
>  		msg->header.message_type = HVMSG_NONE;
>  	}
>  }
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 6ce8b87..aaa2103 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -381,17 +381,12 @@ static void process_chn_event(u32 relid)
>   */
>  void vmbus_on_event(unsigned long data)
>  {
> -	u32 dword;
> -	u32 maxdword;
> -	int bit;
> -	u32 relid;
> -	u32 *recv_int_page = NULL;
> -	void *page_addr;
> +	u32 relid, max_relid;
> +	unsigned long *recv_int_page;
>  	int cpu = smp_processor_id();
> -	union hv_synic_event_flags *event;
> 
>  	if (vmbus_proto_version < VERSION_WIN8) {
> -		maxdword = MAX_NUM_CHANNELS_SUPPORTED >> 5;
> +		max_relid = MAX_NUM_CHANNELS_SUPPORTED;
>  		recv_int_page = vmbus_connection.recv_int_page;
>  	} else {
>  		/*
> @@ -399,36 +394,22 @@ void vmbus_on_event(unsigned long data)
>  		 * can be directly checked to get the id of the channel
>  		 * that has the interrupt pending.
>  		 */
> -		maxdword = HV_EVENT_FLAGS_DWORD_COUNT;
> -		page_addr = hv_context.synic_event_page[cpu];
> -		event = (union hv_synic_event_flags *)page_addr +
> -						 VMBUS_MESSAGE_SINT;
> -		recv_int_page = event->flags32;
> +		struct hv_synic_event_flags *event =
> +			&hv_context.synic_event_page[cpu]->
> +				sintevent_flags[VMBUS_MESSAGE_SINT];
> +		max_relid = HV_EVENT_FLAGS_COUNT;
> +		recv_int_page = (unsigned long *)event->flags;
>  	}
> 
> -
> -
>  	/* Check events */
>  	if (!recv_int_page)
>  		return;
> -	for (dword = 0; dword < maxdword; dword++) {
> -		if (!recv_int_page[dword])
> -			continue;
> -		for (bit = 0; bit < 32; bit++) {
> -			if (sync_test_and_clear_bit(bit,
> -				(unsigned long *)&recv_int_page[dword])) {
> -				relid = (dword << 5) + bit;
> -
> -				if (relid == 0)
> -					/*
> -					 * Special case - vmbus
> -					 * channel protocol msg
> -					 */
> -					continue;
> -
> -				process_chn_event(relid);
> -			}
> -		}
> +
> +	/* relid == 0 is vmbus channel protocol msg */
> +	relid = 1;
> +	for_each_set_bit_from(relid, recv_int_page, max_relid) {
> +		clear_bit(relid, recv_int_page);

We are using this test_and_clear_bit paradigm for locking. The current code
used the sync variant to ensure the host saw the changes we were making
here (clearing the bit). You may want to add a barrier here or use the sync
variant.
 
> +		process_chn_event(relid);
>  	}
>  }
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 230c62e..13dd210 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -872,9 +872,8 @@ static void hv_process_timer_expiration(struct
> hv_message *msg, int cpu)
>  void vmbus_on_msg_dpc(unsigned long data)
>  {
>  	int cpu = smp_processor_id();
> -	void *page_addr = hv_context.synic_message_page[cpu];
> -	struct hv_message *msg = (struct hv_message *)page_addr +
> -				  VMBUS_MESSAGE_SINT;
> +	struct hv_message *msg = &hv_context.synic_message_page[cpu]-
> >
> +
> 	sint_message[VMBUS_MESSAGE_SINT];
>  	struct vmbus_channel_message_header *hdr;
>  	struct vmbus_channel_message_table_entry *entry;
>  	struct onmessage_work_context *ctx;
> @@ -911,54 +910,40 @@ void vmbus_on_msg_dpc(unsigned long data)
>  static void vmbus_isr(void)
>  {
>  	int cpu = smp_processor_id();
> -	void *page_addr;
>  	struct hv_message *msg;
> -	union hv_synic_event_flags *event;
> -	bool handled = false;
> +	struct hv_synic_event_flags *event;
> 
> -	page_addr = hv_context.synic_event_page[cpu];
> -	if (page_addr == NULL)
> +	if (!hv_context.synic_event_page[cpu])
>  		return;
> 
> -	event = (union hv_synic_event_flags *)page_addr +
> -					 VMBUS_MESSAGE_SINT;
> +	event = &hv_context.synic_event_page[cpu]->
> +			sintevent_flags[VMBUS_MESSAGE_SINT];
>  	/*
>  	 * Check for events before checking for messages. This is the order
>  	 * in which events and messages are checked in Windows guests on
>  	 * Hyper-V, and the Windows team suggested we do the same.
>  	 */
> 
> -	if ((vmbus_proto_version == VERSION_WS2008) ||
> -		(vmbus_proto_version == VERSION_WIN7)) {
> -
> +	/* On win8 and above the channel interrupts are signaled directly in
> +	 * the event page and will be checked in the .event_dpc
> +	 */
> +	if (vmbus_proto_version >= VERSION_WIN8 ||
>  		/* Since we are a child, we only need to check bit 0 */
> -		if (sync_test_and_clear_bit(0,
> -			(unsigned long *) &event->flags32[0])) {
> -			handled = true;
> -		}
> -	} else {
> -		/*
> -		 * Our host is win8 or above. The signaling mechanism
> -		 * has changed and we can directly look at the event page.
> -		 * If bit n is set then we have an interrup on the channel
> -		 * whose id is n.
> -		 */
> -		handled = true;
> -	}
> -
> -	if (handled)
> +	    test_and_clear_bit(0, (unsigned long *)event->flags))

Don't we need the sync variant of test_and_clear_bit here.

>  		tasklet_schedule(hv_context.event_dpc[cpu]);
> 
> -
> -	page_addr = hv_context.synic_message_page[cpu];
> -	msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
> +	msg = &hv_context.synic_message_page[cpu]->
> +			sint_message[VMBUS_MESSAGE_SINT];
> 
>  	/* Check if there are actual msgs to be processed */
> -	if (msg->header.message_type != HVMSG_NONE) {
> -		if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
> -			hv_process_timer_expiration(msg, cpu);
> -		else
> -			tasklet_schedule(hv_context.msg_dpc[cpu]);
> +	switch (READ_ONCE(msg->header.message_type)) {
> +	case HVMSG_NONE:
> +		break;
> +	case HVMSG_TIMER_EXPIRED:
> +		hv_process_timer_expiration(msg, cpu);
> +		break;
> +	default:
> +		tasklet_schedule(hv_context.msg_dpc[cpu]);
>  	}
> 
>  	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR, 0);
> --
> 2.9.3

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