linux-kernel - Re: [PATCH V4 12/15] x86/hyper-v: Add HvFlushGuestAddressList hypercall support

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Date:   Mon, 15 Oct 2018 12:30:08 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lantianyu1986@...il.com
Cc:     Lan Tianyu <Tianyu.Lan@...rosoft.com>, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        rkrcmar@...hat.com, devel@...uxdriverproject.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        michael.h.kelley@...rosoft.com, vkuznets@...hat.com
Subject: Re: [PATCH V4 12/15] x86/hyper-v: Add HvFlushGuestAddressList
 hypercall support

On 13/10/2018 16:54, lantianyu1986@...il.com wrote:
> 
> +static int fill_flush_list(union hv_gpa_page_range gpa_list[],
> +		int offset, u64 start_gfn, u64 pages)

Pass the entire struct hv_guest_mapping_flush_list to this function,
it's simpler and it hides the gpa_list argument from
range->parse_flush_list_func.

> +	if (!range->flush_list)
> +		gpa_n = fill_flush_list(flush->gpa_list, gpa_n,
> +				range->start_gfn, range->pages);
> +	else if (range->parse_flush_list_func)
> +		gpa_n = range->parse_flush_list_func(flush->gpa_list, gpa_n,
> +				range->flush_list, fill_flush_list);
> +	else

You are making the code more complicated in order to avoid making
fill_flush_list public.  Just make it public and always go through the
parse_flush_list_func case.  In fact:

- make parse_flush_list_func an argument of hyperv_flush_guest_mapping_range

- drop struct hyperv_tlb_range completely, instead just pass a void* to
hyperv_flush_guest_mapping_range and pass it back to the callback.  The
void * can point to the start_gfn/pages pair, it can be the flush_list,
or anything else.

Paolo