linux-kernel - Re: [PATCH V2 1/3] x86/Hyper-V: Fix definition of struct hv_vp_assist

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Date:   Wed, 14 Aug 2019 15:28:35 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lantianyu1986@...il.com, rkrcmar@...hat.com, corbet@....net,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, x86@...nel.org,
        michael.h.kelley@...rosoft.com
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, vkuznets@...hat.com
Subject: Re: [PATCH V2 1/3] x86/Hyper-V: Fix definition of struct
 hv_vp_assist_page

On 14/08/19 15:26, Paolo Bonzini wrote:
> On 14/08/19 09:34, lantianyu1986@...il.com wrote:
>> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>>
>> The struct hv_vp_assist_page was defined incorrectly.
>> The "vtl_control" should be u64[3], "nested_enlightenments
>> _control" should be a u64 and there is 7 reserved bytes
>> following "enlighten_vmentry". This patch is to fix it.
> 
> How did the assignment to vp_ap->current_nested_vmcs work then?  Does
> the guest simply not care?

... nevermind, I miscounted the length of vtl_control.

Paolo

> Paolo
> 
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>> --
>> Change since v1:
>>        Move definition of struct hv_nested_enlightenments_control
>>        into this patch to fix offset issue.
>> ---
>>  arch/x86/include/asm/hyperv-tlfs.h | 20 +++++++++++++++-----
>>  1 file changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
>> index af78cd72b8f3..cf0b2a04271d 100644
>> --- a/arch/x86/include/asm/hyperv-tlfs.h
>> +++ b/arch/x86/include/asm/hyperv-tlfs.h
>> @@ -514,14 +514,24 @@ struct hv_timer_message_payload {
>>  	__u64 delivery_time;	/* When the message was delivered */
>>  } __packed;
>>  
>> +struct hv_nested_enlightenments_control {
>> +	struct {
>> +		__u32 directhypercall:1;
>> +		__u32 reserved:31;
>> +	} features;
>> +	struct {
>> +		__u32 reserved;
>> +	} hypercallControls;
>> +} __packed;
>> +
>>  /* Define virtual processor assist page structure. */
>>  struct hv_vp_assist_page {
>>  	__u32 apic_assist;
>> -	__u32 reserved;
>> -	__u64 vtl_control[2];
>> -	__u64 nested_enlightenments_control[2];
>> -	__u32 enlighten_vmentry;
>> -	__u32 padding;
>> +	__u32 reserved1;
>> +	__u64 vtl_control[3];
>> +	struct hv_nested_enlightenments_control nested_control;
>> +	__u8 enlighten_vmentry;
>> +	__u8 reserved2[7];
>>  	__u64 current_nested_vmcs;
>>  } __packed;
>>  
>>
>