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From: Jethro Beekman <jethro@fortanix.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
	Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Cedric Xing <cedric.xing@intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	"Dr . Greg Wettstein" <greg@enjellic.com>
Subject: Re: [PATCH 4/7] x86/sgx: Allow userspace to add multiple pages in single ioctl()
Date: Thu, 13 Jun 2019 00:43:42 +0000
Message-ID: <f2e88e83-e5f6-fecb-c180-b75be1d1a582@fortanix.com> (raw)
In-Reply-To: <20190605194845.926-5-sean.j.christopherson@intel.com>

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On 2019-06-05 12:48, Sean Christopherson wrote:
> ...to improve performance when building enclaves by reducing the number
> of user<->system transitions.  Rather than provide arbitrary batching,
> e.g. with per-page SECINFO and mrmask, take advantage of the fact that
> any sane enclave will have large swaths of pages with identical
> properties, e.g. code vs. data sections.
> 
> For simplicity and stability in the initial implementation, loop over
> the existing add page flow instead of taking a more agressive approach,
> which would require tracking transitions between VMAs and holding
> mmap_sem for an extended duration.
> 
> On an error, update the userspace struct to reflect progress made, e.g.
> so that the ioctl can be re-invoked to finish adding pages after a non-
> fatal error.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>   Documentation/x86/sgx/3.API.rst        |   2 +-
>   arch/x86/include/uapi/asm/sgx.h        |  21 ++--
>   arch/x86/kernel/cpu/sgx/driver/ioctl.c | 128 +++++++++++++++++--------
>   3 files changed, 98 insertions(+), 53 deletions(-)
> 
> diff --git a/Documentation/x86/sgx/3.API.rst b/Documentation/x86/sgx/3.API.rst
> index b113aeb05f54..44550aa41073 100644
> --- a/Documentation/x86/sgx/3.API.rst
> +++ b/Documentation/x86/sgx/3.API.rst
> @@ -22,6 +22,6 @@ controls the `PROVISON_KEY` attribute.
>   
>   .. kernel-doc:: arch/x86/kernel/cpu/sgx/driver/ioctl.c
>      :functions: sgx_ioc_enclave_create
> -               sgx_ioc_enclave_add_page
> +               sgx_ioc_enclave_add_region
>                  sgx_ioc_enclave_init
>                  sgx_ioc_enclave_set_attribute
> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
> index 9ed690a38c70..30d114f6b3bd 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -12,8 +12,8 @@
>   
>   #define SGX_IOC_ENCLAVE_CREATE \
>   	_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
> -#define SGX_IOC_ENCLAVE_ADD_PAGE \
> -	_IOW(SGX_MAGIC, 0x01, struct sgx_enclave_add_page)
> +#define SGX_IOC_ENCLAVE_ADD_REGION \
> +	_IOWR(SGX_MAGIC, 0x01, struct sgx_enclave_add_region)
>   #define SGX_IOC_ENCLAVE_INIT \
>   	_IOW(SGX_MAGIC, 0x02, struct sgx_enclave_init)
>   #define SGX_IOC_ENCLAVE_SET_ATTRIBUTE \
> @@ -32,21 +32,22 @@ struct sgx_enclave_create  {
>   };
>   
>   /**
> - * struct sgx_enclave_add_page - parameter structure for the
> - *                               %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
> - * @addr:	address within the ELRANGE
> - * @src:	address for the page data
> - * @secinfo:	address for the SECINFO data
> - * @mrmask:	bitmask for the measured 256 byte chunks
> + * struct sgx_enclave_add_region - parameter structure for the
> + *                                 %SGX_IOC_ENCLAVE_ADD_REGION ioctl
> + * @addr:	start address within the ELRANGE
> + * @src:	start address for the pages' data
> + * @size:	size of region, in bytes
> + * @secinfo:	address of the SECINFO data (common to the entire region)
> + * @mrmask:	bitmask of 256 byte chunks to measure (applied per 4k page)
>    */
> -struct sgx_enclave_add_page {
> +struct sgx_enclave_add_region {
>   	__u64	addr;
>   	__u64	src;
> +	__u64	size;
>   	__u64	secinfo;
>   	__u16	mrmask;

Considering:

1. I might want to load multiple pages that are not consecutive in memory.
2. Repeating mrmask (other than 0 or ~0) doesn't really make sense for 
ranges.

I'd be in favor of an approach that passes an array of 
sgx_enclave_add_page instead.

Somewhat unrelated: have you considered optionally "gifting" enclave 
source pages to the kernel (as in vmsplice)? That would avoid the 
copy_from_user.

--
Jethro Beekman | Fortanix


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  parent reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-05 19:48 [PATCH 0/7] x86/sgx: Clean up and enhance add pages ioctl Sean Christopherson
2019-06-05 19:48 ` [PATCH 1/7] x86/sgx: Remove dead code to handle non-existent IOR ioctl Sean Christopherson
2019-06-05 19:48 ` [PATCH 2/7] x86/sgx: Remove unnecessary @cmd parameter from ioctl helpers Sean Christopherson
2019-06-05 19:48 ` [PATCH 3/7] x86/sgx: Let ioctl helpers do copy to/from user Sean Christopherson
2019-06-05 19:48 ` [PATCH 4/7] x86/sgx: Allow userspace to add multiple pages in single ioctl() Sean Christopherson
2019-06-06 15:47   ` Jarkko Sakkinen
2019-06-13  0:43   ` Jethro Beekman [this message]
2019-06-13 16:51     ` Sean Christopherson
2019-06-13 19:05       ` Andy Lutomirski
2019-06-13 19:15         ` Sean Christopherson
2019-06-13 19:45       ` Xing, Cedric
2019-06-05 19:48 ` [PATCH 5/7] x86/sgx: Add flag to zero added region instead of copying from source Sean Christopherson
2019-06-06 17:20   ` Andy Lutomirski
2019-06-06 17:32     ` Sean Christopherson
2019-06-07 19:32       ` Andy Lutomirski
2019-06-10 17:06         ` Jarkko Sakkinen
2019-06-10 18:09         ` Xing, Cedric
2019-06-10 18:41           ` Sean Christopherson
2019-06-10 18:53         ` Sean Christopherson
2019-06-13  0:38           ` Jethro Beekman
2019-06-13 13:46             ` Sean Christopherson
2019-06-13 16:16               ` Andy Lutomirski
2019-06-13 16:54                 ` Sean Christopherson
2019-06-05 19:48 ` [PATCH 6/7] x86/sgx: Use the actual zero page as the source when adding zero pages Sean Christopherson
2019-06-05 19:48 ` [PATCH 7/7] x86/sgx: Add a reserved field to sgx_enclave_add_region to drop 'packed' Sean Christopherson
2019-06-05 19:59   ` Dave Hansen
2019-06-05 20:00     ` Andy Lutomirski
2019-06-12 15:14   ` Jarkko Sakkinen
2019-06-12 15:23     ` Sean Christopherson
2019-06-13  0:44       ` Jethro Beekman
2019-06-13 15:38       ` Jarkko Sakkinen
2019-06-12 15:16 ` [PATCH 0/7] x86/sgx: Clean up and enhance add pages ioctl Jarkko Sakkinen
2019-06-12 18:14   ` Jarkko Sakkinen

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