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

Kai Huang
2021-01-21T00:08:09Z

On Wed, 20 Jan 2021 14:04:36 +0200 Jarkko Sakkinen wrote:
> 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.

I'll remove it. I don't want to use co-developed-by here.

>
> > 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.

OK. Will add for both sgx_virt_create() and sgx_virt_init().

>
> > +{
> > + 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