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Date: Fri, 5 Mar 2021 14:06:18 +0800
From: Tianyu Lan <ltykernel@...il.com>
To: Vitaly Kuznetsov <vkuznets@...hat.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()
Hi Vitaly:
Thanks for your review.
On 3/4/2021 12:27 AM, Vitaly Kuznetsov wrote:
> 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.
Yes, will add it into commit log.
>
>> 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.
>
Will update.
>> ---
>> 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.
>
Another option is to set host visibility out of vmbus_establish_gpadl().
There are three places calling vmbus_establish_gpadl(). Vmbus, netvsc
and uio drivers.
>> 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);
>
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