Re: [RFC PATCH v3 14/27] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

Kai Huang
2021-02-04T03:54:20Z

Hi Sean,

Do you think is it reasonable to move this patch to KVM? sgx_virt_ecreate() can be
merged to handle ECREATE patch, and sgx_virt_einit() can be merged to handle EINIT
patch. W/o the context of that two patches, it doesn't makes too much sense to have
them standalone under x86 here I think. And nobody except KVM will use them.

On Tue, 2021-01-26 at 22:31 +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>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
> v2->v3:
>
>  - Added kdoc for sgx_virt_ecreate() and sgx_virt_einit(), per Jarkko.
>  - Changed to use CONFIG_X86_SGX_KVM.
>
> ---
>  arch/x86/include/asm/sgx.h | 16 ++++++
>  arch/x86/kernel/cpu/sgx/virt.c | 93 ++++++++++++++++++++++++++++++++++
>  2 files changed, 109 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..8a3ea3e1efbe
> --- /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_KVM
> +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 e1ad7856d878..0f5b0e4e33dd 100644
> --- a/arch/x86/kernel/cpu/sgx/virt.c
> +++ b/arch/x86/kernel/cpu/sgx/virt.c
> @@ -252,3 +252,96 @@ int __init sgx_vepc_init(void)
>
>
>   return misc_register(&sgx_vepc_dev);
>  }
> +
> +/**
> + * sgx_virt_ecreate() - Run ECREATE on behalf of guest
> + * @pageinfo: Pointer to PAGEINFO structure
> + * @secs: Userspace pointer to SECS page
> + * @trapnr: trap number injected to guest in case of ECREATE error
> + *
> + * Run ECREATE on behalf of guest after KVM traps ECREATE for the purpose
> + * of enforcing policies of guest's enclaves, and return the trap number
> + * which should be injected to guest in case of any ECREATE error.
> + *
> + * Return:
> + * - 0: ECREATE was successful.
> + * - -EFAULT: ECREATE returned error.
> + */
> +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;
> +}
> +
> +/**
> + * sgx_virt_ecreate() - Run EINIT on behalf of guest
> + * @sigstruct: Userspace pointer to SIGSTRUCT structure
> + * @token: Userspace pointer to EINITTOKEN structure
> + * @secs: Userspace pointer to SECS page
> + * @lepubkeyhash: Pointer to guest's *virtual* SGX_LEPUBKEYHASH MSR
> + * values
> + * @trapnr: trap number injected to guest in case of EINIT error
> + *
> + * Run EINIT on behalf of guest after KVM traps EINIT. If SGX_LC is available
> + * in host, bare-metal driver may rewrite the hardware values, therefore KVM
> + * needs to update hardware values to guest's virtual MSR values in order to
> + * ensure EINIT is executed with expected hardware values.
> + *
> + * Return:
> + * - 0: EINIT was successful.
> + * - -EFAULT: EINIT returned error.
> + */
> +int sgx_virt_einit(void __user *sigstruct, void __user *token,
> + void __user *secs, u64 *lepubkeyhash, int *trapnr)
> +{
> + 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);