linux-kernel - RE: [Patch v2 4/4] Drivers: hv: Remove hv_free/alloc

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Message-ID:
 <SN6PR02MB4157FD8E8A3E45837BDE17B8D4822@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Thu, 1 May 2025 01:56:10 +0000
From: Michael Kelley <mhklinux@...look.com>
To: "longli@...uxonhyperv.com" <longli@...uxonhyperv.com>, "K. Y. Srinivasan"
	<kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu
	<wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, "linux-hyperv@...r.kernel.org"
	<linux-hyperv@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: Long Li <longli@...rosoft.com>
Subject: RE: [Patch v2 4/4] Drivers: hv: Remove hv_free/alloc_* helpers

From: longli@...uxonhyperv.com <longli@...uxonhyperv.com> Sent: Wednesday, April 30, 2025 3:06 PM
> 
> Those helpers are simply wrappers for page allocations.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>  drivers/hv/connection.c        | 23 +++++++++++++++++------
>  drivers/hv/hv_common.c         | 24 ------------------------
>  include/asm-generic/mshyperv.h |  4 ----
>  3 files changed, 17 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 8351360bba16..a0160b73b593 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c

See my comment in Patch 1 of the series, suggesting that these
changes to connection.c move into Patch 1.

> @@ -206,11 +206,20 @@ int vmbus_connect(void)
>  	INIT_LIST_HEAD(&vmbus_connection.chn_list);
>  	mutex_init(&vmbus_connection.channel_mutex);
> 
> +	/*
> +	 * The following Hyper-V interrupt and monitor pages can be used by
> +	 * UIO for mapping to user-space, it should always be allocated on

s/it should/so should/

> +	 * system page boundaries. We use page allocation functions to allocate
> +	 * those pages. We assume system page be bigger than Hyper-v page.

Instead of your last sentence above, say:

The system page size must be >= the Hyper-V page size.

> +	 */
> +	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
> +
>  	/*
>  	 * Setup the vmbus event connection for channel interrupt
>  	 * abstraction stuff
>  	 */
> -	vmbus_connection.int_page = hv_alloc_hyperv_zeroed_page();
> +	vmbus_connection.int_page =
> +		(void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
>  	if (vmbus_connection.int_page == NULL) {
>  		ret = -ENOMEM;
>  		goto cleanup;
> @@ -225,8 +234,8 @@ int vmbus_connect(void)
>  	 * Setup the monitor notification facility. The 1st page for
>  	 * parent->child and the 2nd page for child->parent
>  	 */
> -	vmbus_connection.monitor_pages[0] = hv_alloc_hyperv_page();
> -	vmbus_connection.monitor_pages[1] = hv_alloc_hyperv_page();
> +	vmbus_connection.monitor_pages[0] = (void *)__get_free_page(GFP_KERNEL);
> +	vmbus_connection.monitor_pages[1] = (void *)__get_free_page(GFP_KERNEL);
>  	if ((vmbus_connection.monitor_pages[0] == NULL) ||
>  	    (vmbus_connection.monitor_pages[1] == NULL)) {
>  		ret = -ENOMEM;
> @@ -342,21 +351,23 @@ void vmbus_disconnect(void)
>  		destroy_workqueue(vmbus_connection.work_queue);
> 
>  	if (vmbus_connection.int_page) {
> -		hv_free_hyperv_page(vmbus_connection.int_page);
> +		free_page((unsigned long)vmbus_connection.int_page);
>  		vmbus_connection.int_page = NULL;
>  	}
> 
>  	if (vmbus_connection.monitor_pages[0]) {
>  		if (!set_memory_encrypted(
>  			(unsigned long)vmbus_connection.monitor_pages[0], 1))
> -			hv_free_hyperv_page(vmbus_connection.monitor_pages[0]);
> +			free_page((unsigned long)
> +				vmbus_connection.monitor_pages[0]);
>  		vmbus_connection.monitor_pages[0] = NULL;
>  	}
> 
>  	if (vmbus_connection.monitor_pages[1]) {
>  		if (!set_memory_encrypted(
>  			(unsigned long)vmbus_connection.monitor_pages[1], 1))
> -			hv_free_hyperv_page(vmbus_connection.monitor_pages[1]);
> +			free_page((unsigned long)
> +				vmbus_connection.monitor_pages[1]);
>  		vmbus_connection.monitor_pages[1] = NULL;
>  	}
>  }
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 297ccd7d4997..421376cea17e 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -105,30 +105,6 @@ void __init hv_common_free(void)
>  	hv_synic_eventring_tail = NULL;
>  }
> 
> -/*
> - * A Hyper-V page can be used by UIO for mapping to user-space, it should
> - * always be allocated on system page boundaries.
> - */
> -void *hv_alloc_hyperv_page(void)
> -{
> -	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
> -	return (void *)__get_free_page(GFP_KERNEL);
> -}
> -EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
> -
> -void *hv_alloc_hyperv_zeroed_page(void)
> -{
> -	BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
> -	return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> -}
> -EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
> -
> -void hv_free_hyperv_page(void *addr)
> -{
> -	free_page((unsigned long)addr);
> -}
> -EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
> -
>  static void *hv_panic_page;
> 
>  /*
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index ccccb1cbf7df..4033508fbb11 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -236,10 +236,6 @@ int hv_common_cpu_init(unsigned int cpu);
>  int hv_common_cpu_die(unsigned int cpu);
>  void hv_identify_partition_type(void);
> 
> -void *hv_alloc_hyperv_page(void);
> -void *hv_alloc_hyperv_zeroed_page(void);
> -void hv_free_hyperv_page(void *addr);
> -
>  /**
>   * hv_cpu_number_to_vp_number() - Map CPU to VP.
>   * @cpu_number: CPU number in Linux terms
> --
> 2.34.1
>