From patchwork Wed Dec 8 00:03:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Zhong X-Patchwork-Id: 12662065 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2BF9C433EF for ; Tue, 7 Dec 2021 15:09:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237781AbhLGPMm (ORCPT ); Tue, 7 Dec 2021 10:12:42 -0500 Received: from mga14.intel.com ([192.55.52.115]:5480 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229503AbhLGPMl (ORCPT ); Tue, 7 Dec 2021 10:12:41 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10190"; a="237820979" X-IronPort-AV: E=Sophos;i="5.87,293,1631602800"; d="scan'208";a="237820979" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Dec 2021 07:09:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,293,1631602800"; d="scan'208";a="461289739" Received: from icx.bj.intel.com ([10.240.192.117]) by orsmga003.jf.intel.com with ESMTP; 07 Dec 2021 07:09:05 -0800 From: Yang Zhong To: x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, pbonzini@redhat.com Cc: seanjc@google.com, jun.nakajima@intel.com, kevin.tian@intel.com, jing2.liu@linux.intel.com, jing2.liu@intel.com, yang.zhong@intel.com Subject: [PATCH 01/19] x86/fpu: Extend prctl() with guest permissions Date: Tue, 7 Dec 2021 19:03:41 -0500 Message-Id: <20211208000359.2853257-2-yang.zhong@intel.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211208000359.2853257-1-yang.zhong@intel.com> References: <20211208000359.2853257-1-yang.zhong@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Thomas Gleixner Add guest permission control for dynamic XSTATE components, including extension to prctl() with two new options (ARCH_GET_XCOMP_GUEST_PERM and ARCH_REQ_XCOMP_GUEST_PERM) and to struct fpu with a new member (guest_perm). Userspace VMM has to request guest permissions before it exposes any XSAVE feature using dynamic XSTATE components. The permission can be set only once when the first vCPU is created. A new flag FPU_GUEST_PERM_LOCKED is introduced to lock the change for this purpose Similar to native permissions this doesn't actually enable the permitted feature. KVM is expected to install a larger kernel buffer and enable the feature when detecting the intention from the guest. Signed-off-by: Thomas Gleixner Signed-off-by: Jing Liu Signed-off-by: Yang Zhong --- (To Thomas) We change the definition of xstate_get_guest_group_perm() from xstate.h to api.h since this will be called by KVM. arch/x86/include/asm/fpu/api.h | 2 ++ arch/x86/include/asm/fpu/types.h | 9 ++++++ arch/x86/include/uapi/asm/prctl.h | 26 ++++++++-------- arch/x86/kernel/fpu/core.c | 3 ++ arch/x86/kernel/fpu/xstate.c | 50 +++++++++++++++++++++++-------- arch/x86/kernel/fpu/xstate.h | 13 ++++++-- arch/x86/kernel/process.c | 2 ++ 7 files changed, 78 insertions(+), 27 deletions(-) diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index 6053674f9132..7532f73c82a6 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -138,6 +138,8 @@ static inline void fpstate_free(struct fpu *fpu) { } /* fpstate-related functions which are exported to KVM */ extern void fpstate_clear_xstate_component(struct fpstate *fps, unsigned int xfeature); +extern inline u64 xstate_get_guest_group_perm(void); + /* KVM specific functions */ extern bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu); extern void fpu_free_guest_fpstate(struct fpu_guest *gfpu); diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 3c06c82ab355..6ddf80637697 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -387,6 +387,8 @@ struct fpstate { /* @regs is dynamically sized! Don't add anything after @regs! */ } __aligned(64); +#define FPU_GUEST_PERM_LOCKED BIT_ULL(63) + struct fpu_state_perm { /* * @__state_perm: @@ -476,6 +478,13 @@ struct fpu { */ struct fpu_state_perm perm; + /* + * @guest_perm: + * + * Permission related information for guest pseudo FPUs + */ + struct fpu_state_perm guest_perm; + /* * @__fpstate: * diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 754a07856817..500b96e71f18 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -2,20 +2,22 @@ #ifndef _ASM_X86_PRCTL_H #define _ASM_X86_PRCTL_H -#define ARCH_SET_GS 0x1001 -#define ARCH_SET_FS 0x1002 -#define ARCH_GET_FS 0x1003 -#define ARCH_GET_GS 0x1004 +#define ARCH_SET_GS 0x1001 +#define ARCH_SET_FS 0x1002 +#define ARCH_GET_FS 0x1003 +#define ARCH_GET_GS 0x1004 -#define ARCH_GET_CPUID 0x1011 -#define ARCH_SET_CPUID 0x1012 +#define ARCH_GET_CPUID 0x1011 +#define ARCH_SET_CPUID 0x1012 -#define ARCH_GET_XCOMP_SUPP 0x1021 -#define ARCH_GET_XCOMP_PERM 0x1022 -#define ARCH_REQ_XCOMP_PERM 0x1023 +#define ARCH_GET_XCOMP_SUPP 0x1021 +#define ARCH_GET_XCOMP_PERM 0x1022 +#define ARCH_REQ_XCOMP_PERM 0x1023 +#define ARCH_GET_XCOMP_GUEST_PERM 0x1024 +#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025 -#define ARCH_MAP_VDSO_X32 0x2001 -#define ARCH_MAP_VDSO_32 0x2002 -#define ARCH_MAP_VDSO_64 0x2003 +#define ARCH_MAP_VDSO_X32 0x2001 +#define ARCH_MAP_VDSO_32 0x2002 +#define ARCH_MAP_VDSO_64 0x2003 #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 8ea306b1bf8e..ab19b3d8b2f7 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -450,6 +450,8 @@ void fpstate_reset(struct fpu *fpu) fpu->perm.__state_perm = fpu_kernel_cfg.default_features; fpu->perm.__state_size = fpu_kernel_cfg.default_size; fpu->perm.__user_state_size = fpu_user_cfg.default_size; + /* Same defaults for guests */ + fpu->guest_perm = fpu->perm; } static inline void fpu_inherit_perms(struct fpu *dst_fpu) @@ -460,6 +462,7 @@ static inline void fpu_inherit_perms(struct fpu *dst_fpu) spin_lock_irq(¤t->sighand->siglock); /* Fork also inherits the permissions of the parent */ dst_fpu->perm = src_fpu->perm; + dst_fpu->guest_perm = src_fpu->guest_perm; spin_unlock_irq(¤t->sighand->siglock); } } diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index d28829403ed0..9856d579aa6e 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1595,7 +1595,7 @@ static int validate_sigaltstack(unsigned int usize) return 0; } -static int __xstate_request_perm(u64 permitted, u64 requested) +static int __xstate_request_perm(u64 permitted, u64 requested, bool guest) { /* * This deliberately does not exclude !XSAVES as we still might @@ -1605,6 +1605,7 @@ static int __xstate_request_perm(u64 permitted, u64 requested) */ bool compacted = cpu_feature_enabled(X86_FEATURE_XSAVES); struct fpu *fpu = ¤t->group_leader->thread.fpu; + struct fpu_state_perm *perm; unsigned int ksize, usize; u64 mask; int ret; @@ -1621,15 +1622,18 @@ static int __xstate_request_perm(u64 permitted, u64 requested) mask &= XFEATURE_MASK_USER_SUPPORTED; usize = xstate_calculate_size(mask, false); - ret = validate_sigaltstack(usize); - if (ret) - return ret; + if (!guest) { + ret = validate_sigaltstack(usize); + if (ret) + return ret; + } + perm = guest ? &fpu->guest_perm : &fpu->perm; /* Pairs with the READ_ONCE() in xstate_get_group_perm() */ - WRITE_ONCE(fpu->perm.__state_perm, requested); + WRITE_ONCE(perm->__state_perm, requested); /* Protected by sighand lock */ - fpu->perm.__state_size = ksize; - fpu->perm.__user_state_size = usize; + perm->__state_size = ksize; + perm->__user_state_size = usize; return ret; } @@ -1640,7 +1644,7 @@ static const u64 xstate_prctl_req[XFEATURE_MAX] = { [XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE_DATA, }; -static int xstate_request_perm(unsigned long idx) +static int xstate_request_perm(unsigned long idx, bool guest) { u64 permitted, requested; int ret; @@ -1661,14 +1665,19 @@ static int xstate_request_perm(unsigned long idx) return -EOPNOTSUPP; /* Lockless quick check */ - permitted = xstate_get_host_group_perm(); + permitted = xstate_get_group_perm(guest); if ((permitted & requested) == requested) return 0; /* Protect against concurrent modifications */ spin_lock_irq(¤t->sighand->siglock); - permitted = xstate_get_host_group_perm(); - ret = __xstate_request_perm(permitted, requested); + permitted = xstate_get_group_perm(guest); + + /* First vCPU allocation locks the permissions. */ + if (guest && (permitted & FPU_GUEST_PERM_LOCKED)) + ret = -EBUSY; + else + ret = __xstate_request_perm(permitted, requested, guest); spin_unlock_irq(¤t->sighand->siglock); return ret; } @@ -1713,12 +1722,17 @@ int xfd_enable_feature(u64 xfd_err) return 0; } #else /* CONFIG_X86_64 */ -static inline int xstate_request_perm(unsigned long idx) +static inline int xstate_request_perm(unsigned long idx, bool guest) { return -EPERM; } #endif /* !CONFIG_X86_64 */ +inline u64 xstate_get_guest_group_perm(void) +{ + return xstate_get_group_perm(true); +} +EXPORT_SYMBOL_GPL(xstate_get_guest_group_perm); /** * fpu_xstate_prctl - xstate permission operations * @tsk: Redundant pointer to current @@ -1742,6 +1756,7 @@ long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2) u64 __user *uptr = (u64 __user *)arg2; u64 permitted, supported; unsigned long idx = arg2; + bool guest = false; if (tsk != current) return -EPERM; @@ -1760,11 +1775,20 @@ long fpu_xstate_prctl(struct task_struct *tsk, int option, unsigned long arg2) permitted &= XFEATURE_MASK_USER_SUPPORTED; return put_user(permitted, uptr); + case ARCH_GET_XCOMP_GUEST_PERM: + permitted = xstate_get_guest_group_perm(); + permitted &= XFEATURE_MASK_USER_SUPPORTED; + return put_user(permitted, uptr); + + case ARCH_REQ_XCOMP_GUEST_PERM: + guest = true; + fallthrough; + case ARCH_REQ_XCOMP_PERM: if (!IS_ENABLED(CONFIG_X86_64)) return -EOPNOTSUPP; - return xstate_request_perm(idx); + return xstate_request_perm(idx, guest); default: return -EINVAL; diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h index 86ea7c0fa2f6..98a472775c97 100644 --- a/arch/x86/kernel/fpu/xstate.h +++ b/arch/x86/kernel/fpu/xstate.h @@ -20,10 +20,19 @@ static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask) xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT; } -static inline u64 xstate_get_host_group_perm(void) +static inline u64 xstate_get_group_perm(bool guest) { + struct fpu *fpu = ¤t->group_leader->thread.fpu; + struct fpu_state_perm *perm; + /* Pairs with WRITE_ONCE() in xstate_request_perm() */ - return READ_ONCE(current->group_leader->thread.fpu.perm.__state_perm); + perm = guest ? &fpu->guest_perm : &fpu->perm; + return READ_ONCE(perm->__state_perm); +} + +static inline u64 xstate_get_host_group_perm(void) +{ + return xstate_get_group_perm(false); } enum xstate_copy_mode { diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 04143a653a8a..d7bc23589062 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -993,6 +993,8 @@ long do_arch_prctl_common(struct task_struct *task, int option, case ARCH_GET_XCOMP_SUPP: case ARCH_GET_XCOMP_PERM: case ARCH_REQ_XCOMP_PERM: + case ARCH_GET_XCOMP_GUEST_PERM: + case ARCH_REQ_XCOMP_GUEST_PERM: return fpu_xstate_prctl(task, option, arg2); }