From: lon...@linuxonhyperv.com <lon...@linuxonhyperv.com> Sent: Wednesday,
April 30, 2025 3:06 PM
>
> There are use cases that interrupt and monitor pages are mapped to
> user-mode through UIO, they need to be system page aligned. Some Hyper-V
s/UIO, they/UIO, so they/
> allocation APIs introduced earlier broke those requirements.
>
> Fix those APIs by always allocating Hyper-V page at system page boundaries.
This patch modifies hv_alloc_hyperv_page() and friends. Then Patch 4 of the
series deletes them, including the modifications. It would be less code motion
to do the first part of Patch 4 (i.e., the use of __get_free_page directly in
connection.c) here in Patch 1, and leave hv_alloc_hyperv_page() and friends
unmodified. Continue to make the change to hv_kmsg_dump_register() here
in Patch 1 as well.
Then have Patch 2 simply delete hv_alloc_hyperv_page() and friends
because they are no longer used. The modifications to hv_alloc_hyperv_page()
and friends would not be needed.
Patch 3 and 4 would be the additional changes in uio_hv_generic.c.
Michael
>
> Cc: sta...@vger.kernel.org
> Fixes: ca48739e59df ("Drivers: hv: vmbus: Move Hyper-V page allocator to arch
> neutral code")
> Signed-off-by: Long Li <lon...@microsoft.com>
> ---
> drivers/hv/hv_common.c | 35 ++++++++++-------------------------
> 1 file changed, 10 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index a7d7494feaca..297ccd7d4997 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -106,41 +106,26 @@ void __init hv_common_free(void)
> }
>
> /*
> - * Functions for allocating and freeing memory with size and
> - * alignment HV_HYP_PAGE_SIZE. These functions are needed because
> - * the guest page size may not be the same as the Hyper-V page
> - * size. We depend upon kmalloc() aligning power-of-two size
> - * allocations to the allocation size boundary, so that the
> - * allocated memory appears to Hyper-V as a page of the size
> - * it expects.
> + * 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);
> -
> - if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> - return (void *)__get_free_page(GFP_KERNEL);
> - else
> - return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> + 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)
> {
> - if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> - return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
> - else
> - return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> + 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)
> {
> - if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
> - free_page((unsigned long)addr);
> - else
> - kfree(addr);
> + free_page((unsigned long)addr);
> }
> EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
>
> @@ -272,7 +257,7 @@ static void hv_kmsg_dump_unregister(void)
> atomic_notifier_chain_unregister(&panic_notifier_list,
> &hyperv_panic_report_block);
>
> - hv_free_hyperv_page(hv_panic_page);
> + kfree(hv_panic_page);
> hv_panic_page = NULL;
> }
>
> @@ -280,7 +265,7 @@ static void hv_kmsg_dump_register(void)
> {
> int ret;
>
> - hv_panic_page = hv_alloc_hyperv_zeroed_page();
> + hv_panic_page = kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
> if (!hv_panic_page) {
> pr_err("Hyper-V: panic message page memory allocation
> failed\n");
> return;
> @@ -289,7 +274,7 @@ static void hv_kmsg_dump_register(void)
> ret = kmsg_dump_register(&hv_kmsg_dumper);
> if (ret) {
> pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
> - hv_free_hyperv_page(hv_panic_page);
> + kfree(hv_panic_page);
> hv_panic_page = NULL;
> }
> }
> --
> 2.34.1
>
