linux-kernel - Re: [PATCH v2 04/13] powerpc/pseries/svm: Add helpers for UV_SHARE_PAGE and UV_UNSHARE

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Date:   Thu, 18 Jul 2019 17:12:47 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Anshuman Khandual <anshuman.linux@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mike Anderson <andmike@...ux.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Ram Pai <linuxram@...ibm.com>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>
Subject: Re: [PATCH v2 04/13] powerpc/pseries/svm: Add helpers for UV_SHARE_PAGE and UV_UNSHARE_PAGE


Hello Alexey,

Thanks for your review!

Alexey Kardashevskiy <aik@...abs.ru> writes:

> On 13/07/2019 16:00, Thiago Jung Bauermann wrote:
>> From: Ram Pai <linuxram@...ibm.com>
>>
>> These functions are used when the guest wants to grant the hypervisor
>> access to certain pages.
>>
>> Signed-off-by: Ram Pai <linuxram@...ibm.com>
>> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
>> ---
>>   arch/powerpc/include/asm/ultravisor-api.h |  2 ++
>>   arch/powerpc/include/asm/ultravisor.h     | 15 +++++++++++++++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
>> index fe9a0d8d7673..c7513bbadf57 100644
>> --- a/arch/powerpc/include/asm/ultravisor-api.h
>> +++ b/arch/powerpc/include/asm/ultravisor-api.h
>> @@ -25,6 +25,8 @@
>>   #define UV_UNREGISTER_MEM_SLOT		0xF124
>>   #define UV_PAGE_IN			0xF128
>>   #define UV_PAGE_OUT			0xF12C
>> +#define UV_SHARE_PAGE			0xF130
>> +#define UV_UNSHARE_PAGE			0xF134
>>   #define UV_PAGE_INVAL			0xF138
>>   #define UV_SVM_TERMINATE		0xF13C
>>   diff --git a/arch/powerpc/include/asm/ultravisor.h
>> b/arch/powerpc/include/asm/ultravisor.h
>> index f5dc5af739b8..f7418b663a0e 100644
>> --- a/arch/powerpc/include/asm/ultravisor.h
>> +++ b/arch/powerpc/include/asm/ultravisor.h
>> @@ -91,6 +91,21 @@ static inline int uv_svm_terminate(u64 lpid)
>>     	return ucall(UV_SVM_TERMINATE, retbuf, lpid);
>>   }
>> +
>> +static inline int uv_share_page(u64 pfn, u64 npages)
>> +{
>> +	unsigned long retbuf[UCALL_BUFSIZE];
>> +
>> +	return ucall(UV_SHARE_PAGE, retbuf, pfn, npages);
>
>
> What is in that retbuf? Can you pass NULL instead?

I think so, that buffer isn't used actually. Claudio is working on a
ucall_norets() which doesn't take the buffer and I can switch to that.

--
Thiago Jung Bauermann
IBM Linux Technology Center