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 18:13:37 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     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



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?


> +}
> +
> +static inline int uv_unshare_page(u64 pfn, u64 npages)
> +{
> +	unsigned long retbuf[UCALL_BUFSIZE];
> +
> +	return ucall(UV_UNSHARE_PAGE, retbuf, pfn, npages);
> +}
> +
>   #endif /* !__ASSEMBLY__ */
>   
>   #endif	/* _ASM_POWERPC_ULTRAVISOR_H */
> 

-- 
Alexey