Re: [RFC PATCH v5 13/26] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM

Jarkko Sakkinen
2021-02-16T03:10:26Z

On Tue, Feb 16, 2021 at 05:08:20AM +0200, Jarkko Sakkinen wrote:
> On Sun, Feb 14, 2021 at 02:29:15AM +1300, Kai Huang wrote:
> > From: Sean Christopherson <sean.j.christopherson@intel.com>
> >
> > The host kernel must intercept ECREATE to be able to impose policies on
> > guests. When it does this, the host 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>
> > ---
> > v4->v5:
> >
> > - No code change.
> >
> > v3->v4:
> >
> > - Added one new line before last return in sgx_virt_einit(), per Jarkko.
> >
> > 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 | 94 ++++++++++++++++++++++++++++++++++
> > 2 files changed, 110 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);
>
> s/virt/vepc/g
>
> > +#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 47542140f8c1..016bad7cff8d 100644
> > --- a/arch/x86/kernel/cpu/sgx/virt.c
> > +++ b/arch/x86/kernel/cpu/sgx/virt.c
>
> Rename as vepc.c.
>
> > @@ -257,3 +257,97 @@ 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);
>
> Empty line.
>
> > + 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();
>
> Ditto.
>
> > + return ret;
> > +}
> > +
> > +/**
> > + * sgx_virt_einit() - 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, SGX driver may rewrite the hardware values at wish, 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);

Remove exports.

> > --
> > 2.29.2
> >
> >
>
> /Jarkko