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X-CSE-ConnectionGUID: gn+q8SB5Rgm7rzQ5JnD+cg== X-CSE-MsgGUID: 5RcmavH9QtGiwFL9AHKuKw== X-IronPort-AV: E=McAfee;i="6700,10204,11363"; a="42202307" X-IronPort-AV: E=Sophos;i="6.14,221,1736841600"; d="scan'208";a="42202307" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2025 14:50:31 -0800 X-CSE-ConnectionGUID: gbqYRql8TV+FDo28CzqB6A== X-CSE-MsgGUID: VOax7jffTVO2U8+anUc4sg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="118413778" Received: from kinlongk-mobl1.amr.corp.intel.com (HELO [10.125.109.165]) ([10.125.109.165]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2025 14:50:30 -0800 Message-ID: Date: Tue, 4 Mar 2025 14:50:48 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/6] x86/fpu/xstate: Introduce fpu_guest_cfg for guest FPU configuration To: Chao Gao , tglx@linutronix.de, x86@kernel.org, seanjc@google.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: peterz@infradead.org, rick.p.edgecombe@intel.com, mlevitsk@redhat.com, weijiang.yang@intel.com, john.allen@amd.com References: <20241126101710.62492-1-chao.gao@intel.com> <20241126101710.62492-5-chao.gao@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/26/24 02:17, Chao Gao wrote: > From: Yang Weijiang > > Define new fpu_guest_cfg to hold all guest FPU settings so that it can > differ from generic kernel FPU settings, e.g., enabling CET supervisor > xstate by default for guest fpstate while it's remained disabled in > kernel FPU config. > > The kernel dynamic xfeatures are specifically used by guest fpstate now, > add the mask for guest fpstate so that guest_perm.__state_perm == > (fpu_kernel_cfg.default_xfeature | XFEATURE_MASK_KERNEL_DYNAMIC). And > if guest fpstate is re-allocated to hold user dynamic xfeatures, the > resulting permissions are consumed before calculate new guest fpstate. This kinda restates what the code does, but I don't think it matches the code. > With new guest FPU config added, there're 3 categories of FPU configs in > kernel, the usages and key fields are recapped as below. This changelog is pretty rough. It's got a lot of words but not much substance. > kernel FPU config: > @fpu_kernel_cfg.max_features > - all known and CPU supported user and supervisor features except > independent kernel features > > @fpu_kernel_cfg.default_features > - all known and CPU supported user and supervisor features except > dynamic kernel features, independent kernel features and dynamic > userspace features. > > @fpu_kernel_cfg.max_size > - size of compacted buffer with 'fpu_kernel_cfg.max_features' > > @fpu_kernel_cfg.default_size > - size of compacted buffer with 'fpu_kernel_cfg.default_features' > > user FPU config: > @fpu_user_cfg.max_features > - all known and CPU supported user features > > @fpu_user_cfg.default_features > - all known and CPU supported user features except dynamic userspace > features. > > @fpu_user_cfg.max_size > - size of non-compacted buffer with 'fpu_user_cfg.max_features' > > @fpu_user_cfg.default_size > - size of non-compacted buffer with 'fpu_user_cfg.default_features' > > guest FPU config: > @fpu_guest_cfg.max_features > - all known and CPU supported user and supervisor features except > independent kernel features. > > @fpu_guest_cfg.default_features > - all known and CPU supported user and supervisor features except > independent kernel features and dynamic userspace features. > > @fpu_guest_cfg.max_size > - size of compacted buffer with 'fpu_guest_cfg.max_features' > > @fpu_guest_cfg.default_size > - size of compacted buffer with 'fpu_guest_cfg.default_features' This looks like kerneldoc, not changelog. Are you sure you want it _here_? > diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h > index b49e65120d34..da6583a1c0a2 100644 > --- a/arch/x86/include/asm/fpu/types.h > +++ b/arch/x86/include/asm/fpu/types.h > @@ -611,6 +611,6 @@ struct fpu_state_config { > }; > > /* FPU state configuration information */ > -extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg; > +extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg, fpu_guest_cfg; > > #endif /* _ASM_X86_FPU_TYPES_H */ > diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c > index 1209c7aebb21..9e2e5c46cf28 100644 > --- a/arch/x86/kernel/fpu/core.c > +++ b/arch/x86/kernel/fpu/core.c > @@ -33,9 +33,10 @@ DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic); > DEFINE_PER_CPU(u64, xfd_state); > #endif > > -/* The FPU state configuration data for kernel and user space */ > +/* The FPU state configuration data for kernel, user space and guest. */ > struct fpu_state_config fpu_kernel_cfg __ro_after_init; > struct fpu_state_config fpu_user_cfg __ro_after_init; > +struct fpu_state_config fpu_guest_cfg __ro_after_init; > > /* > * Represents the initial FPU state. It's mostly (but not completely) zeroes, > @@ -536,8 +537,15 @@ 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; > + > + /* Guest permission settings */ > + fpu->guest_perm.__state_perm = fpu_guest_cfg.default_features; > + fpu->guest_perm.__state_size = fpu_guest_cfg.default_size; > + /* > + * Set guest's __user_state_size to fpu_user_cfg.default_size so that > + * existing uAPIs can still work. > + */ > + fpu->guest_perm.__user_state_size = fpu_user_cfg.default_size; > } > > static inline void fpu_inherit_perms(struct fpu *dst_fpu) > diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c > index c38e477e3e45..17c3255dfa41 100644 > --- a/arch/x86/kernel/fpu/xstate.c > +++ b/arch/x86/kernel/fpu/xstate.c > @@ -686,6 +686,7 @@ static int __init init_xstate_size(void) > { > /* Recompute the context size for enabled features: */ > unsigned int user_size, kernel_size, kernel_default_size; > + unsigned int guest_default_size; > bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED); > > /* Uncompacted user space size */ > @@ -707,13 +708,18 @@ static int __init init_xstate_size(void) > kernel_default_size = > xstate_calculate_size(fpu_kernel_cfg.default_features, compacted); > > + guest_default_size = > + xstate_calculate_size(fpu_guest_cfg.default_features, compacted); > + > if (!paranoid_xstate_size_valid(kernel_size)) > return -EINVAL; > > fpu_kernel_cfg.max_size = kernel_size; > fpu_user_cfg.max_size = user_size; > + fpu_guest_cfg.max_size = kernel_size; > > fpu_kernel_cfg.default_size = kernel_default_size; > + fpu_guest_cfg.default_size = guest_default_size; > fpu_user_cfg.default_size = > xstate_calculate_size(fpu_user_cfg.default_features, false); > > @@ -829,6 +835,10 @@ void __init fpu__init_system_xstate(unsigned int legacy_size) > fpu_user_cfg.default_features = fpu_user_cfg.max_features; > fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; > > + fpu_guest_cfg.max_features = fpu_kernel_cfg.max_features; > + fpu_guest_cfg.default_features = fpu_guest_cfg.max_features; > + fpu_guest_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; I thought this was saying above that it was _setting_ dynamic features. Why _not_ set them by default?