netdev - Re: [PATCH V6 7/8] Drivers: hv: vmbus: Add SNP support for VMbus channel initiate message

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Message-ID: <1c31c18d-af76-c5af-84f1-0dafe48f8605@gmail.com>
Date:   Sat, 2 Oct 2021 22:39:56 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Michael Kelley <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
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        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
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Cc:     "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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        "dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: Re: [PATCH V6 7/8] Drivers: hv: vmbus: Add SNP support for VMbus
 channel initiate message

Hi Michael:
      Thanks for your review.


On 10/2/2021 9:26 PM, Michael Kelley wrote:
>> @@ -303,10 +365,26 @@ void vmbus_disconnect(void)
>>   		vmbus_connection.int_page = NULL;
>>   	}
>>
>> -	hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[0]);
>> -	hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[1]);
>> -	vmbus_connection.monitor_pages[0] = NULL;
>> -	vmbus_connection.monitor_pages[1] = NULL;
>> +	if (hv_is_isolation_supported()) {
>> +		memunmap(vmbus_connection.monitor_pages[0]);
>> +		memunmap(vmbus_connection.monitor_pages[1]);
> The matching memremap() calls are made in vmbus_connect() only in the
> SNP case.  In the non-SNP case, monitor_pages and monitor_pages_original
> are the same, so you would be doing an unmap, and then doing the
> set_memory_encrypted() and hv_free_hyperv_page() using an address
> that is no longer mapped, which seems wrong.   Looking at memunmap(),
> it might be a no-op in this case, but even if it is, making them conditional
> on the SNP case might be a safer thing to do, and it would make the code
> more symmetrical.
>

Yes, memumap() does nothing is the non-SNP CVM and so I didn't check CVM
type here. I will add the check in the next version.

Thanks.