Re: [PATCH V9 9/9] virtio: Intel IFC VF driver for VDPA

["Zhu, Lingshan" <lingshan.zhu@intel.com>]

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On 4/10/2020 4:25 AM, Michael S. Tsirkin wrote:
> On Thu, Apr 09, 2020 at 12:41:13PM +0200, Arnd Bergmann wrote:
>> On Thu, Mar 26, 2020 at 3:08 PM Jason Wang <jasowang@redhat.com> wrote:
>>> From: Zhu Lingshan <lingshan.zhu@intel.com>
>>>
>>> This commit introduced two layers to drive IFC VF:
>>>
>>> (1) ifcvf_base layer, which handles IFC VF NIC hardware operations and
>>>      configurations.
>>>
>>> (2) ifcvf_main layer, which complies to VDPA bus framework,
>>>      implemented device operations for VDPA bus, handles device probe,
>>>      bus attaching, vring operations, etc.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
>>> Signed-off-by: Bie Tiwei <tiwei.bie@intel.com>
>>> Signed-off-by: Wang Xiao <xiao.w.wang@intel.com>
>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> +
>>> +#define IFCVF_QUEUE_ALIGNMENT  PAGE_SIZE
>>> +#define IFCVF_QUEUE_MAX                32768
>>> +static u16 ifcvf_vdpa_get_vq_align(struct vdpa_device *vdpa_dev)
>>> +{
>>> +       return IFCVF_QUEUE_ALIGNMENT;
>>> +}
>> This fails to build on arm64 with 64kb page size (found in linux-next):
>>
>> /drivers/vdpa/ifcvf/ifcvf_main.c: In function 'ifcvf_vdpa_get_vq_align':
>> arch/arm64/include/asm/page-def.h:17:20: error: conversion from 'long
>> unsigned int' to 'u16' {aka 'short unsigned int'} changes value from
>> '65536' to '0' [-Werror=overflow]
>>     17 | #define PAGE_SIZE  (_AC(1, UL) << PAGE_SHIFT)
>>        |                    ^
>> drivers/vdpa/ifcvf/ifcvf_base.h:37:31: note: in expansion of macro 'PAGE_SIZE'
>>     37 | #define IFCVF_QUEUE_ALIGNMENT PAGE_SIZE
>>        |                               ^~~~~~~~~
>> drivers/vdpa/ifcvf/ifcvf_main.c:231:9: note: in expansion of macro
>> 'IFCVF_QUEUE_ALIGNMENT'
>>    231 |  return IFCVF_QUEUE_ALIGNMENT;
>>        |         ^~~~~~~~~~~~~~~~~~~~~
>>
>> It's probably good enough to just not allow the driver to be built in that
>> configuration as it's fairly rare but unfortunately there is no simple Kconfig
>> symbol for it.
>>
>> In a similar driver, we did
>>
>> config VMXNET3
>>          tristate "VMware VMXNET3 ethernet driver"
>>          depends on PCI && INET
>>          depends on !(PAGE_SIZE_64KB || ARM64_64K_PAGES || \
>>                       IA64_PAGE_SIZE_64KB || MICROBLAZE_64K_PAGES || \
>>                       PARISC_PAGE_SIZE_64KB || PPC_64K_PAGES)
>>
>> I think we should probably make PAGE_SIZE_64KB a global symbol
>> in arch/Kconfig and have it selected by the other symbols so drivers
>> like yours can add a dependency for it.
>>
>>           Arnd
> It's probably easier to make the alignment u32 - I don't really know why it's
> u16, all callers seem to assign the result to a u32 value.

Thanks Michael!

@ Arnd, would you please kindly have a try on the attached patch? I 
failed to find an armv8 or above platform for now.

Thanks
BR
Zhu Lingshan

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From bb2019f0620609fbbdc6854bccc5fefdb53f3d9d Mon Sep 17 00:00:00 2001
From: Zhu Lingshan <lingshan.zhu@intel.com>
Date: Fri, 10 Apr 2020 11:04:38 +0800
Subject: [PATCH] vdpa: change get_vq_align() to u32 alignment

This commit change the return value of get_vq_align() to u32. this
can help resolve a build issue of arm64 platform, and adapting to
the callers.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
---
 drivers/vdpa/ifcvf/ifcvf_main.c  | 2 +-
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 +-
 include/linux/vdpa.h             | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
index 8d54dc5..970895c 100644
--- a/drivers/vdpa/ifcvf/ifcvf_main.c
+++ b/drivers/vdpa/ifcvf/ifcvf_main.c
@@ -228,7 +228,7 @@ static u32 ifcvf_vdpa_get_vendor_id(struct vdpa_device *vdpa_dev)
 	return IFCVF_SUBSYS_VENDOR_ID;
 }
 
-static u16 ifcvf_vdpa_get_vq_align(struct vdpa_device *vdpa_dev)
+static u32 ifcvf_vdpa_get_vq_align(struct vdpa_device *vdpa_dev)
 {
 	return IFCVF_QUEUE_ALIGNMENT;
 }
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 6e8a0cf..a4b3f0d 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -435,7 +435,7 @@ static u64 vdpasim_get_vq_state(struct vdpa_device *vdpa, u16 idx)
 	return vrh->last_avail_idx;
 }
 
-static u16 vdpasim_get_vq_align(struct vdpa_device *vdpa)
+static u32 vdpasim_get_vq_align(struct vdpa_device *vdpa)
 {
 	return VDPASIM_QUEUE_ALIGN;
 }
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 733acfb..5453af8 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -164,7 +164,7 @@ struct vdpa_config_ops {
 	u64 (*get_vq_state)(struct vdpa_device *vdev, u16 idx);
 
 	/* Device ops */
-	u16 (*get_vq_align)(struct vdpa_device *vdev);
+	u32 (*get_vq_align)(struct vdpa_device *vdev);
 	u64 (*get_features)(struct vdpa_device *vdev);
 	int (*set_features)(struct vdpa_device *vdev, u64 features);
 	void (*set_config_cb)(struct vdpa_device *vdev,
-- 
1.8.3.1