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Date: Sat, 5 Sep 2020 00:19:08 +0000
From: Michael Kelley <mikelley@...rosoft.com>
To: Boqun Feng <boqun.feng@...il.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
CC: KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
Wei Liu <wei.liu@...nel.org>, Jiri Kosina <jikos@...nel.org>,
Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
"James E.J. Bottomley" <jejb@...ux.ibm.com>,
"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: RE: [RFC v2 03/11] Drivers: hv: vmbus: Introduce types of GPADL
From: Boqun Feng <boqun.feng@...il.com> Sent: Tuesday, September 1, 2020 8:01 PM
>
> This patch introduces two types of GPADL: HV_GPADL_{BUFFER, RING}. The
> types of GPADL are purely the concept in the guest, IOW the hypervisor
> treat them as the same.
>
> The reason of introducing the types of GPADL is to support guests whose
s/of/for/
> page size is not 4k (the page size of Hyper-V hypervisor). In these
> guests, both the headers and the data parts of the ringbuffers need to
> be aligned to the PAGE_SIZE, because 1) some of the ringbuffers will be
> mapped into userspace and 2) we use "double mapping" mechanism to
> support fast wrap-around, and "double mapping" relies on ringbuffers
> being page-aligned. However, the Hyper-V hypervisor only uses 4k
> (HV_HYP_PAGE_SIZE) headers. Our solution to this is that we always make
> the headers of ringbuffers take one guest page and when GPADL is
> established between the guest and hypervisor, the only first 4k of
> header is used. To handle this special case, we need the types of GPADL
> to differ different guest memory usage for GPADL.
>
> Type enum is introduced along with several general interfaces to
> describe the differences between normal buffer GPADL and ringbuffer
> GPADL.
>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> ---
> drivers/hv/channel.c | 159 +++++++++++++++++++++++++++++++++++------
> include/linux/hyperv.h | 44 +++++++++++-
> 2 files changed, 182 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 1cbe8fc931fc..7c443fd567e4 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -35,6 +35,98 @@ static unsigned long virt_to_hvpfn(void *addr)
> return paddr >> HV_HYP_PAGE_SHIFT;
> }
>
> +/*
> + * hv_gpadl_size - Return the real size of a gpadl, the size that Hyper-V uses
> + *
> + * For BUFFER gpadl, Hyper-V uses the exact same size as the guest does.
> + *
> + * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the header
> + * (because of the alignment requirement), however, the hypervisor only
> + * uses the first HV_HYP_PAGE_SIZE as the header, therefore leaving a
> + * (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap. And since there are two rings in a
> + * ringbuffer, So the total size for a RING gpadl that Hyper-V uses is the
Unneeded word "So"
> + * total size that the guest uses minus twice of the gap size.
> + */
> +static inline u32 hv_gpadl_size(enum hv_gpadl_type type, u32 size)
> +{
> + switch (type) {
> + case HV_GPADL_BUFFER:
> + return size;
> + case HV_GPADL_RING:
> + /* The size of a ringbuffer must be page-aligned */
> + BUG_ON(size % PAGE_SIZE);
> + /*
> + * Two things to notice here:
> + * 1) We're processing two ring buffers as a unit
> + * 2) We're skipping any space larger than HV_HYP_PAGE_SIZE in
> + * the first guest-size page of each of the two ring buffers.
> + * So we effectively subtract out two guest-size pages, and add
> + * back two Hyper-V size pages.
> + */
> + return size - 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
> + }
> + BUG();
> + return 0;
> +}
> +
> +/*
> + * hv_ring_gpadl_send_offset - Calculate the send offset in a ring gpadl based
> + * on the offset in the guest
> + *
> + * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
> + * virtual address space of the guest
> + */
> +static inline u32 hv_ring_gpadl_send_offset(u32 send_offset)
> +{
> +
> + /*
> + * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the
> + * header (because of the alignment requirement), however, the
> + * hypervisor only uses the first HV_HYP_PAGE_SIZE as the header,
> + * therefore leaving a (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap.
> + *
> + * And to calculate the effective send offset in gpadl, we need to
> + * substract this gap.
> + */
> + return send_offset - (PAGE_SIZE - HV_HYP_PAGE_SIZE);
> +}
> +
> +/*
> + * hv_gpadl_hvpfn - Return the Hyper-V page PFN of the @i th Hyper-V page in
> + * the gpadl
> + *
> + * @type: the type of the gpadl
> + * @kbuffer: the pointer to the gpadl in the guest
> + * @size: the total size (in bytes) of the gpadl
> + * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
> + * virtual address space of the guest
> + * @i: the index
> + */
> +static inline u64 hv_gpadl_hvpfn(enum hv_gpadl_type type, void *kbuffer,
> + u32 size, u32 send_offset, int i)
> +{
> + int send_idx = hv_ring_gpadl_send_offset(send_offset) >> HV_HYP_PAGE_SHIFT;
> + unsigned long delta = 0UL;
> +
> + switch (type) {
> + case HV_GPADL_BUFFER:
> + break;
> + case HV_GPADL_RING:
> + if (i == 0)
> + delta = 0;
> + else if (i <= send_idx)
> + delta = PAGE_SIZE - HV_HYP_PAGE_SIZE;
> + else
> + delta = 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
> + break;
> + default:
> + BUG();
> + break;
> + }
> +
> + return virt_to_hvpfn(kbuffer + delta + (HV_HYP_PAGE_SIZE * i));
> +}
> +
> /*
> * vmbus_setevent- Trigger an event notification on the specified
> * channel.
> @@ -160,7 +252,8 @@ EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);
> /*
> * create_gpadl_header - Creates a gpadl for the specified buffer
> */
> -static int create_gpadl_header(void *kbuffer, u32 size,
> +static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
> + u32 size, u32 send_offset,
> struct vmbus_channel_msginfo **msginfo)
> {
> int i;
> @@ -173,7 +266,7 @@ static int create_gpadl_header(void *kbuffer, u32 size,
>
> int pfnsum, pfncount, pfnleft, pfncurr, pfnsize;
>
> - pagecount = size >> HV_HYP_PAGE_SHIFT;
> + pagecount = hv_gpadl_size(type, size) >> HV_HYP_PAGE_SHIFT;
>
> /* do we need a gpadl body msg */
> pfnsize = MAX_SIZE_CHANNEL_MESSAGE -
> @@ -200,10 +293,10 @@ static int create_gpadl_header(void *kbuffer, u32 size,
> gpadl_header->range_buflen = sizeof(struct gpa_range) +
> pagecount * sizeof(u64);
> gpadl_header->range[0].byte_offset = 0;
> - gpadl_header->range[0].byte_count = size;
> + gpadl_header->range[0].byte_count = hv_gpadl_size(type, size);
> for (i = 0; i < pfncount; i++)
> - gpadl_header->range[0].pfn_array[i] = virt_to_hvpfn(
> - kbuffer + HV_HYP_PAGE_SIZE * i);
> + gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
> + type, kbuffer, size, send_offset, i);
> *msginfo = msgheader;
>
> pfnsum = pfncount;
> @@ -254,8 +347,8 @@ static int create_gpadl_header(void *kbuffer, u32 size,
> * so the hypervisor guarantees that this is ok.
> */
> for (i = 0; i < pfncurr; i++)
> - gpadl_body->pfn[i] = virt_to_hvpfn(
> - kbuffer + HV_HYP_PAGE_SIZE * (pfnsum + i));
> + gpadl_body->pfn[i] = hv_gpadl_hvpfn(type,
> + kbuffer, size, send_offset, pfnsum + i);
>
> /* add to msg header */
> list_add_tail(&msgbody->msglistentry,
> @@ -281,10 +374,10 @@ static int create_gpadl_header(void *kbuffer, u32 size,
> gpadl_header->range_buflen = sizeof(struct gpa_range) +
> pagecount * sizeof(u64);
> gpadl_header->range[0].byte_offset = 0;
> - gpadl_header->range[0].byte_count = size;
> + gpadl_header->range[0].byte_count = hv_gpadl_size(type, size);
> for (i = 0; i < pagecount; i++)
> - gpadl_header->range[0].pfn_array[i] = virt_to_hvpfn(
> - kbuffer + HV_HYP_PAGE_SIZE * i);
> + gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
> + type, kbuffer, size, send_offset, i);
>
> *msginfo = msgheader;
> }
> @@ -297,15 +390,20 @@ static int create_gpadl_header(void *kbuffer, u32 size,
> }
>
> /*
> - * vmbus_establish_gpadl - Establish a GPADL for the specified buffer
> + * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
> *
> * @channel: a channel
> + * @type: the type of the corresponding GPADL, only meaningful for the guest.
> * @kbuffer: from kmalloc or vmalloc
> * @size: page-size multiple
> + * @send_offset: the offset (in bytes) where the send ring buffer starts,
> + * should be 0 for BUFFER type gpadl
> * @gpadl_handle: some funky thing
> */
> -int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
> - u32 size, u32 *gpadl_handle)
> +static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> + enum hv_gpadl_type type, void *kbuffer,
> + u32 size, u32 send_offset,
> + u32 *gpadl_handle)
> {
> struct vmbus_channel_gpadl_header *gpadlmsg;
> struct vmbus_channel_gpadl_body *gpadl_body;
> @@ -319,7 +417,7 @@ int vmbus_establish_gpadl(struct vmbus_channel *channel, void
> *kbuffer,
> next_gpadl_handle =
> (atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);
>
> - ret = create_gpadl_header(kbuffer, size, &msginfo);
> + ret = create_gpadl_header(type, kbuffer, size, send_offset, &msginfo);
> if (ret)
> return ret;
>
> @@ -400,6 +498,21 @@ int vmbus_establish_gpadl(struct vmbus_channel *channel, void
> *kbuffer,
> kfree(msginfo);
> return ret;
> }
> +
> +/*
> + * vmbus_establish_gpadl - Establish a GPADL for the specified buffer
> + *
> + * @channel: a channel
> + * @kbuffer: from kmalloc or vmalloc
> + * @size: page-size multiple
> + * @gpadl_handle: some funky thing
> + */
> +int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
> + u32 size, u32 *gpadl_handle)
> +{
> + return __vmbus_establish_gpadl(channel, HV_GPADL_BUFFER, kbuffer, size,
> + 0U, gpadl_handle);
> +}
> EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
>
> static int __vmbus_open(struct vmbus_channel *newchannel,
> @@ -438,10 +551,11 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> /* Establish the gpadl for the ring buffer */
> newchannel->ringbuffer_gpadlhandle = 0;
>
> - err = vmbus_establish_gpadl(newchannel,
> - page_address(newchannel->ringbuffer_page),
> - (send_pages + recv_pages) << PAGE_SHIFT,
> - &newchannel->ringbuffer_gpadlhandle);
> + err = __vmbus_establish_gpadl(newchannel, HV_GPADL_RING,
> + page_address(newchannel->ringbuffer_page),
> + (send_pages + recv_pages) << PAGE_SHIFT,
> + newchannel->ringbuffer_send_offset << PAGE_SHIFT,
> + &newchannel->ringbuffer_gpadlhandle);
> if (err)
> goto error_clean_ring;
>
> @@ -462,7 +576,13 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> open_msg->openid = newchannel->offermsg.child_relid;
> open_msg->child_relid = newchannel->offermsg.child_relid;
> open_msg->ringbuffer_gpadlhandle = newchannel->ringbuffer_gpadlhandle;
> - open_msg->downstream_ringbuffer_pageoffset = newchannel-
> >ringbuffer_send_offset;
> + /*
> + * The unit of ->downstream_ringbuffer_pageoffset is HV_HYP_PAGE and
> + * the unit of ->ringbuffer_send_offset is PAGE, so here we first
> + * calculate it into bytes and then convert into HV_HYP_PAGE.
> + */
> + open_msg->downstream_ringbuffer_pageoffset =
> + hv_ring_gpadl_send_offset(newchannel->ringbuffer_send_offset << PAGE_SHIFT) >> HV_HYP_PAGE_SHIFT;
Line length?
> open_msg->target_vp = hv_cpu_number_to_vp_number(newchannel->target_cpu);
>
> if (userdatalen)
> @@ -556,7 +676,6 @@ int vmbus_open(struct vmbus_channel *newchannel,
> }
> EXPORT_SYMBOL_GPL(vmbus_open);
>
> -
> /*
> * vmbus_teardown_gpadl -Teardown the specified GPADL handle
> */
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 38100e80360a..7d16dd28aa48 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -29,6 +29,48 @@
>
> #pragma pack(push, 1)
>
> +/*
> + * Types for GPADL, decides is how GPADL header is created.
> + *
> + * It doesn't make much difference between BUFFER and RING if PAGE_SIZE is the
> + * same as HV_HYP_PAGE_SIZE.
> + *
> + * If PAGE_SIZE is bigger than HV_HYP_PAGE_SIZE, the headers of ring buffers
> + * will be of PAGE_SIZE, however, only the first HV_HYP_PAGE will be put
> + * into gpadl, therefore the number for HV_HYP_PAGE and the indexes of each
> + * HV_HYP_PAGE will be different between different types of GPADL, for example
> + * if PAGE_SIZE is 64K:
> + *
> + * BUFFER:
> + *
> + * gva: |-- 64k --|-- 64k --| ... |
> + * gpa: | 4k | 4k | ... | 4k | 4k | 4k | ... | 4k |
> + * index: 0 1 2 15 16 17 18 .. 31 32 ...
> + * | | ... | | | ... | ...
> + * v V V V V V
> + * gpadl: | 4k | 4k | ... | 4k | 4k | 4k | ... | 4k | ... |
> + * index: 0 1 2 ... 15 16 17 18 .. 31 32 ...
> + *
> + * RING:
> + *
> + * | header | data | header | data |
> + * gva: |-- 64k --|-- 64k --| ... |-- 64k --|-- 64k --| ... |
> + * gpa: | 4k | .. | 4k | 4k | ... | 4k | ... | 4k | .. | 4k | .. | ... |
> + * index: 0 1 16 17 18 31 ... n n+1 n+16 ... 2n
> + * | / / / | / /
> + * | / / / | / /
> + * | / / ... / ... | / ... /
> + * | / / / | / /
> + * | / / / | / /
> + * V V V V V V v
> + * gpadl: | 4k | 4k | ... | ... | 4k | 4k | ... |
> + * index: 0 1 2 ... 16 ... n-15 n-14 n-13 ... 2n-30
> + */
> +enum hv_gpadl_type {
> + HV_GPADL_BUFFER,
> + HV_GPADL_RING
> +};
> +
> /* Single-page buffer */
> struct hv_page_buffer {
> u32 len;
> @@ -111,7 +153,7 @@ struct hv_ring_buffer {
> } feature_bits;
>
> /* Pad it to PAGE_SIZE so that data starts on page boundary */
> - u8 reserved2[4028];
> + u8 reserved2[PAGE_SIZE - 68];
>
> /*
> * Ring data starts here + RingDataStartOffset
> --
> 2.28.0
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