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Date: Wed, 03 Mar 2021 17:27:38 +0100
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Tianyu Lan <ltykernel@...il.com>
Cc: Tianyu Lan <Tianyu.Lan@...rosoft.com>,
linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, thomas.lendacky@....com,
brijesh.singh@....com, sunilmut@...rosoft.com, kys@...rosoft.com,
haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
hpa@...or.com, davem@...emloft.net, kuba@...nel.org,
gregkh@...uxfoundation.org
Subject: Re: [RFC PATCH 1/12] x86/Hyper-V: Add visibility parameter for
vmbus_establish_gpadl()
Tianyu Lan <ltykernel@...il.com> writes:
> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>
> Add visibility parameter for vmbus_establish_gpadl() and prepare
> to change host visibility when create gpadl for buffer.
>
"No functional change" as you don't actually use the parameter.
> Signed-off-by: Sunil Muthuswamy <sunilmut@...rosoft.com>
> Co-Developed-by: Sunil Muthuswamy <sunilmut@...rosoft.com>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
Nit: Sunil's SoB looks misleading because the patch is from you,
Co-Developed-by should be sufficient.
> ---
> arch/x86/include/asm/hyperv-tlfs.h | 9 +++++++++
> drivers/hv/channel.c | 20 +++++++++++---------
> drivers/net/hyperv/netvsc.c | 8 ++++++--
> drivers/uio/uio_hv_generic.c | 7 +++++--
> include/linux/hyperv.h | 3 ++-
> 5 files changed, 33 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index e6cd3fee562b..fb1893a4c32b 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -236,6 +236,15 @@ enum hv_isolation_type {
> /* TSC invariant control */
> #define HV_X64_MSR_TSC_INVARIANT_CONTROL 0x40000118
>
> +/* Hyper-V GPA map flags */
> +#define HV_MAP_GPA_PERMISSIONS_NONE 0x0
> +#define HV_MAP_GPA_READABLE 0x1
> +#define HV_MAP_GPA_WRITABLE 0x2
> +
> +#define VMBUS_PAGE_VISIBLE_READ_ONLY HV_MAP_GPA_READABLE
> +#define VMBUS_PAGE_VISIBLE_READ_WRITE (HV_MAP_GPA_READABLE|HV_MAP_GPA_WRITABLE)
> +#define VMBUS_PAGE_NOT_VISIBLE HV_MAP_GPA_PERMISSIONS_NONE
> +
Are these x86-only? If not, then we should probably move these defines
to include/asm-generic/hyperv-tlfs.h. In case they are, we should do
something as we're using them from arch neutral places.
Also, could you please add a comment stating that these flags define
host's visibility of a page and not guest's (this seems to be not
obvious at least to me).
> /*
> * Declare the MSR used to setup pages used to communicate with the hypervisor.
> */
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 0bd202de7960..daa21cc72beb 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -242,7 +242,7 @@ EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);
> */
> static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
> u32 size, u32 send_offset,
> - struct vmbus_channel_msginfo **msginfo)
> + struct vmbus_channel_msginfo **msginfo, u32 visibility)
> {
> int i;
> int pagecount;
> @@ -391,7 +391,7 @@ static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
> static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> enum hv_gpadl_type type, void *kbuffer,
> u32 size, u32 send_offset,
> - u32 *gpadl_handle)
> + u32 *gpadl_handle, u32 visibility)
> {
> struct vmbus_channel_gpadl_header *gpadlmsg;
> struct vmbus_channel_gpadl_body *gpadl_body;
> @@ -405,7 +405,8 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> next_gpadl_handle =
> (atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);
>
> - ret = create_gpadl_header(type, kbuffer, size, send_offset, &msginfo);
> + ret = create_gpadl_header(type, kbuffer, size, send_offset,
> + &msginfo, visibility);
> if (ret)
> return ret;
>
> @@ -496,10 +497,10 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> * @gpadl_handle: some funky thing
> */
> int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
> - u32 size, u32 *gpadl_handle)
> + u32 size, u32 *gpadl_handle, u32 visibility)
> {
> return __vmbus_establish_gpadl(channel, HV_GPADL_BUFFER, kbuffer, size,
> - 0U, gpadl_handle);
> + 0U, gpadl_handle, visibility);
> }
> EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
>
> @@ -610,10 +611,11 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> newchannel->ringbuffer_gpadlhandle = 0;
>
> 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);
> + page_address(newchannel->ringbuffer_page),
> + (send_pages + recv_pages) << PAGE_SHIFT,
> + newchannel->ringbuffer_send_offset << PAGE_SHIFT,
> + &newchannel->ringbuffer_gpadlhandle,
> + VMBUS_PAGE_VISIBLE_READ_WRITE);
Nit: I liked the original alignment more and we can avoid the unneeded
code churn.
> if (err)
> goto error_clean_ring;
>
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index 2353623259f3..bb72c7578330 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -333,7 +333,8 @@ static int netvsc_init_buf(struct hv_device *device,
> */
> ret = vmbus_establish_gpadl(device->channel, net_device->recv_buf,
> buf_size,
> - &net_device->recv_buf_gpadl_handle);
> + &net_device->recv_buf_gpadl_handle,
> + VMBUS_PAGE_VISIBLE_READ_WRITE);
> if (ret != 0) {
> netdev_err(ndev,
> "unable to establish receive buffer's gpadl\n");
> @@ -422,10 +423,13 @@ static int netvsc_init_buf(struct hv_device *device,
> /* Establish the gpadl handle for this buffer on this
> * channel. Note: This call uses the vmbus connection rather
> * than the channel to establish the gpadl handle.
> + * Send buffer should theoretically be only marked as "read-only", but
> + * the netvsp for some reason needs write capabilities on it.
> */
> ret = vmbus_establish_gpadl(device->channel, net_device->send_buf,
> buf_size,
> - &net_device->send_buf_gpadl_handle);
> + &net_device->send_buf_gpadl_handle,
> + VMBUS_PAGE_VISIBLE_READ_WRITE);
> if (ret != 0) {
> netdev_err(ndev,
> "unable to establish send buffer's gpadl\n");
> diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> index 0330ba99730e..813a7bee5139 100644
> --- a/drivers/uio/uio_hv_generic.c
> +++ b/drivers/uio/uio_hv_generic.c
> @@ -29,6 +29,7 @@
> #include <linux/hyperv.h>
> #include <linux/vmalloc.h>
> #include <linux/slab.h>
> +#include <asm/mshyperv.h>
>
> #include "../hv/hyperv_vmbus.h"
>
> @@ -295,7 +296,8 @@ hv_uio_probe(struct hv_device *dev,
> }
>
> ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
> - RECV_BUFFER_SIZE, &pdata->recv_gpadl);
> + RECV_BUFFER_SIZE, &pdata->recv_gpadl,
> + VMBUS_PAGE_VISIBLE_READ_WRITE);
> if (ret)
> goto fail_close;
>
> @@ -315,7 +317,8 @@ hv_uio_probe(struct hv_device *dev,
> }
>
> ret = vmbus_establish_gpadl(channel, pdata->send_buf,
> - SEND_BUFFER_SIZE, &pdata->send_gpadl);
> + SEND_BUFFER_SIZE, &pdata->send_gpadl,
> + VMBUS_PAGE_VISIBLE_READ_ONLY);
Actually, this is the only place where you use 'READ_ONLY' mapping --
which makes me wonder if it's actually worth it or we can hard-code
VMBUS_PAGE_VISIBLE_READ_WRITE for now and avoid this additional
parameter.
> if (ret)
> goto fail_close;
>
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index f1d74dcf0353..016fdca20d6e 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1179,7 +1179,8 @@ extern int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
> extern int vmbus_establish_gpadl(struct vmbus_channel *channel,
> void *kbuffer,
> u32 size,
> - u32 *gpadl_handle);
> + u32 *gpadl_handle,
> + u32 visibility);
>
> extern int vmbus_teardown_gpadl(struct vmbus_channel *channel,
> u32 gpadl_handle);
--
Vitaly
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