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

[Jarkko Sakkinen <jarkko@kernel.org>]

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