linux-kernel - Re: [Resend RFC PATCH V2 03/12] x86/Hyper-V: Add new hvcall guest address host visibility support

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Date:   Wed, 14 Apr 2021 17:40:28 +0200
From:   Christoph Hellwig <hch@....de>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     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, arnd@...db.de,
        akpm@...ux-foundation.org, gregkh@...uxfoundation.org,
        konrad.wilk@...cle.com, hch@....de, m.szyprowski@...sung.com,
        robin.murphy@....com, joro@...tes.org, will@...nel.org,
        davem@...emloft.net, kuba@...nel.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-scsi@...r.kernel.org,
        netdev@...r.kernel.org, vkuznets@...hat.com,
        thomas.lendacky@....com, brijesh.singh@....com,
        sunilmut@...rosoft.com
Subject: Re: [Resend RFC PATCH V2 03/12] x86/Hyper-V: Add new hvcall guest
 address host visibility support

> +/*
> + * hv_set_mem_host_visibility - Set host visibility for specified memory.
> + */

I don't think this comment really clarifies anything over the function
name.  What is 'host visibility'

> +int hv_set_mem_host_visibility(void *kbuffer, u32 size, u32 visibility)

Should size be a size_t?
Should visibility be an enum of some kind?

> +int hv_mark_gpa_visibility(u16 count, const u64 pfn[], u32 visibility)

Not sure what this does either.

> +	local_irq_save(flags);
> +	input_pcpu = (struct hv_input_modify_sparse_gpa_page_host_visibility **)

Is there a chance we could find a shorter but still descriptive
name for this variable?  Why do we need the cast?

> +#define VMBUS_PAGE_VISIBLE_READ_ONLY HV_MAP_GPA_READABLE
> +#define VMBUS_PAGE_VISIBLE_READ_WRITE (HV_MAP_GPA_READABLE|HV_MAP_GPA_WRITABLE)

pointlessly overlong line.