Re: [RFC PATCH v2 13/26] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

Jarkko Sakkinen
2021-01-20T13:46:27Z

On Mon, Jan 18, 2021 at 04:28:06PM +1300, Kai Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> The bare-metal kernel must intercept ECREATE to be able to impose policies
> on guests. When it does this, the bare-metal kernel runs ECREATE against
> the userspace mapping of the virtualized EPC.
>
> Provide wrappers around __ecreate() and __einit() to hide the ugliness
> of overloading the ENCLS return value to encode multiple error formats
> in a single int. KVM will trap-and-execute ECREATE and EINIT as part
> of SGX virtualization, and on an exception, KVM needs the trapnr so that
> it can inject the correct fault into the guest.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> [Kai: Use sgx_update_lepubkeyhash() to update pubkey hash MSRs.]

If you have to go to this, please instead use co-developed-by.

> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
> v1->v2:
>
> - Refined commit msg based on Dave's comment.
> - Added comment to explain why to use __uaccess_xxx().
> ---
> arch/x86/include/asm/sgx.h | 16 +++++++++
> arch/x86/kernel/cpu/sgx/virt.c | 61 ++++++++++++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
> create mode 100644 arch/x86/include/asm/sgx.h
>
> diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
> new file mode 100644
> index 000000000000..0d643b985085
> --- /dev/null
> +++ b/arch/x86/include/asm/sgx.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_SGX_H
> +#define _ASM_X86_SGX_H
> +
> +#include <linux/types.h>
> +
> +#ifdef CONFIG_X86_SGX_VIRTUALIZATION
> +struct sgx_pageinfo;
> +
> +int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
> + int *trapnr);
> +int sgx_virt_einit(void __user *sigstruct, void __user *token,
> + void __user *secs, u64 *lepubkeyhash, int *trapnr);
> +#endif
> +
> +#endif /* _ASM_X86_SGX_H */
> diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
> index 1e8620f20651..97f02e5235ca 100644
> --- a/arch/x86/kernel/cpu/sgx/virt.c
> +++ b/arch/x86/kernel/cpu/sgx/virt.c
> @@ -253,3 +253,64 @@ int __init sgx_virt_epc_init(void)
>
> return misc_register(&sgx_virt_epc_dev);
> }
> +
> +int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs,
> + int *trapnr)
> +{
> + int ret;
> +
> + /*
> + * @secs is userspace address, and it's not guaranteed @secs points at
> + * an actual EPC page. It's also possible to generate a kernel mapping
> + * to physical EPC page by resolving PFN but using __uaccess_xx() is
> + * simpler.
> + */
> + __uaccess_begin();
> + ret = __ecreate(pageinfo, (void *)secs);
> + __uaccess_end();
> +
> + if (encls_faulted(ret)) {
> + *trapnr = ENCLS_TRAPNR(ret);
> + return -EFAULT;
> + }
> +
> + /* ECREATE doesn't return an error code, it faults or succeeds. */
> + WARN_ON_ONCE(ret);
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(sgx_virt_ecreate);
> +
> +static int __sgx_virt_einit(void __user *sigstruct, void __user *token,
> + void __user *secs)
> +{
> + int ret;
> +
> + __uaccess_begin();
> + ret = __einit((void *)sigstruct, (void *)token, (void *)secs);
> + __uaccess_end();
> + return ret;
> +}
> +
> +int sgx_virt_einit(void __user *sigstruct, void __user *token,
> + void __user *secs, u64 *lepubkeyhash, int *trapnr)

kdoc missing.

> +{
> + int ret;
> +
> + if (!boot_cpu_has(X86_FEATURE_SGX_LC)) {
> + ret = __sgx_virt_einit(sigstruct, token, secs);
> + } else {
> + preempt_disable();
> +
> + sgx_update_lepubkeyhash(lepubkeyhash);
> +
> + ret = __sgx_virt_einit(sigstruct, token, secs);
> + preempt_enable();
> + }
> +
> + if (encls_faulted(ret)) {
> + *trapnr = ENCLS_TRAPNR(ret);
> + return -EFAULT;
> + }
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(sgx_virt_einit);
> --
> 2.29.2
>
>

/Jarkko