linux-kernel - Re: [PATCH 4/6] x86: hv: mmu.c: Replace page definitions with Hyper-V specific ones

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Date:   Fri, 05 Apr 2019 13:10:46 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maya Nakamura <m.maya.nakamura@...il.com>, mikelley@...rosoft.com,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org
Cc:     x86@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] x86: hv: mmu.c: Replace page definitions with Hyper-V specific ones

Maya Nakamura <m.maya.nakamura@...il.com> writes:

> Replace PAGE_SHIFT, PAGE_SIZE, and PAGE_MASK with HV_HYP_PAGE_SHIFT,
> HV_HYP_PAGE_SIZE, and HV_HYP_PAGE_MASK, respectively, because the guest
> page size and hypervisor page size concepts are different, even though
> they happen to be the same value on x86.
>
> Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> ---
>  arch/x86/hyperv/mmu.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
> index e65d7fe6489f..175f6dcc7362 100644
> --- a/arch/x86/hyperv/mmu.c
> +++ b/arch/x86/hyperv/mmu.c
> @@ -15,7 +15,7 @@
>  #include <asm/trace/hyperv.h>
>  
>  /* Each gva in gva_list encodes up to 4096 pages to flush */
> -#define HV_TLB_FLUSH_UNIT (4096 * PAGE_SIZE)
> +#define HV_TLB_FLUSH_UNIT (4096 * HV_HYP_PAGE_SIZE)
>  
>  static u64 hyperv_flush_tlb_others_ex(const struct cpumask *cpus,
>  				      const struct flush_tlb_info *info);
> @@ -32,15 +32,15 @@ static inline int fill_gva_list(u64 gva_list[], int offset,
>  	do {
>  		diff = end > cur ? end - cur : 0;
>  
> -		gva_list[gva_n] = cur & PAGE_MASK;
> +		gva_list[gva_n] = cur & HV_HYP_PAGE_MASK;

I'm not sure this is correct: here we're expressing guest virtual
addresses in need of flushing, this should be unrelated to the
hypervisor page size.

>  		/*
>  		 * Lower 12 bits encode the number of additional
>  		 * pages to flush (in addition to the 'cur' page).
>  		 */
>  		if (diff >= HV_TLB_FLUSH_UNIT)
> -			gva_list[gva_n] |= ~PAGE_MASK;
> +			gva_list[gva_n] |= ~HV_HYP_PAGE_MASK;
>  		else if (diff)
> -			gva_list[gva_n] |= (diff - 1) >> PAGE_SHIFT;
> +			gva_list[gva_n] |= (diff - 1) >> HV_HYP_PAGE_SHIFT;
>  
>  		cur += HV_TLB_FLUSH_UNIT;
>  		gva_n++;
> @@ -129,7 +129,8 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,
>  	 * We can flush not more than max_gvas with one hypercall. Flush the
>  	 * whole address space if we were asked to do more.
>  	 */
> -	max_gvas = (PAGE_SIZE - sizeof(*flush)) / sizeof(flush->gva_list[0]);
> +	max_gvas = (HV_HYP_PAGE_SIZE - sizeof(*flush)) /
> +		    sizeof(flush->gva_list[0]);
>  
>  	if (info->end == TLB_FLUSH_ALL) {
>  		flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;
> @@ -200,9 +201,9 @@ static u64 hyperv_flush_tlb_others_ex(const struct cpumask *cpus,
>  	 * whole address space if we were asked to do more.
>  	 */
>  	max_gvas =
> -		(PAGE_SIZE - sizeof(*flush) - nr_bank *
> +		(HV_HYP_PAGE_SIZE - sizeof(*flush) - nr_bank *
>  		 sizeof(flush->hv_vp_set.bank_contents[0])) /
> -		sizeof(flush->gva_list[0]);
> +		 sizeof(flush->gva_list[0]);
>  
>  	if (info->end == TLB_FLUSH_ALL) {
>  		flush->flags |= HV_FLUSH_NON_GLOBAL_MAPPINGS_ONLY;

-- 
Vitaly