From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 343AA2D480D for ; Wed, 17 Sep 2025 12:47:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758113275; cv=none; b=Mai0lU4FM9JJHu5N7Skh0vaomYi5HEnLpGoRHgeSy1U+zSDI1iLeqNCYt3zKxV9VJYLlPKp1dz1c8CPs6dzoLh/x1MjhSW9IeujDZW+dasFY/yn/qdEmDW4LdCgZhZmmH9WNdrbB68ZsiIaRUnYHtmXSr/vaAyMT8xy4EXpWj9U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758113275; c=relaxed/simple; bh=RQINUxGsJC4fFGW9Pga0A1D4M8TL6sYnSYVhtigYag8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=bEMEiCGuUxhe69ZEFoRCY1ckV9HYwoQjVvo0XjVUcdXnf6LDf9ynlsyNHeLSzxMm2P6DYzDsfnkWcntDuclpyIkz3G+zEPEKJ+ixCLp2Y7U2Ks72TE2cdWBXroVwv+7S2L2o7VqsX/hT6RrRDCXjVTfpkeBrsEODSHkP/DLw54s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=eqPcO/cH; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eqPcO/cH" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2507ae2fa99so122539635ad.1 for ; Wed, 17 Sep 2025 05:47:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1758113273; x=1758718073; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=hhI+ZLb55QOi22SZbshrFRw3Xyx04NRrqgLS645MTmk=; b=eqPcO/cHXAGggYBHwZa3SOXFPA7g/R2o/g31T02no00DMewtGvJiN+jPWEJVqq2eTH d7iwScULz59ascoz3pmUqiBPuZZ4LIbbL2VrTMqlgzJ2hg5ILkxrAgtxuJAvArx2Uf8f EVlUGi/ZTI6GQVUs5W+94hwZwpKI4zAMaVJE83HJXZ8cfa/qaBFYdpepToGkHuKo0v7a NlgD2rXSuYCP9nqTbCi9lIFSq1wvPmrdolHfaPPmeeiFel0psZRocWYDktshAPZNn4ff RV5NYtRygn6X3fsK9x50fpwxAyovzfvVSRCZ5lR+8Fad9haQBAifPe1XokHElewbv7CP YqyA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758113273; x=1758718073; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=hhI+ZLb55QOi22SZbshrFRw3Xyx04NRrqgLS645MTmk=; b=GgOmn5z2onphXeX35T7pwc8RGny0ViMtiSVhDF8h3BrVUctjPBHbBxcjkAc2RXN2rY ertU6crkrKA6rWYjQf+UZTHGnwYFOlMuEu37/Tm3+GyNEa2JqAPfaF1e0N9jJGE7ZpbG M8vNjnAxF8geibNIC+Kv/pSWliTrBm6n9dBbO0Gfe9/MZrPkbuYgM2/KrhL0bgLsZBMQ pHIpCF+fThRSuVtc6fA8l7dV07EKkdAkXsj7+AzUvhQ6fUFB0ODFpJ1XmEPxCvpp9RzE cx7adVKNYQl2sKvF3H/yXX6/TEYpasMnBMa8OD9bUhPkcvH/mrAWww1Iy4xwPdXFovjG V8gw== X-Forwarded-Encrypted: i=1; AJvYcCXs2BNVQyw4NYfJ2my88kwJAyk/6P9NeK4Gw6NI7OBxCL3ktXdeZ6MGjSwsN8lDN1rk2PzqN+TDhq5rD/0=@vger.kernel.org X-Gm-Message-State: AOJu0YxOv4zVa0ZAf5FLzDjP6H+whTQcGw5FABK7IIIyOE/ynl4j2mN7 e2srNlPR7s1dZ4Fh5QMjsjaCKDGmb/eo1GA1Qn3dFL0PBg/9IZH+udpJeRPYQXIdaskSlOzV63B 1XTwTcA== X-Google-Smtp-Source: AGHT+IGZMZLBQ8oPAPbG5AROKZBqoW5d8+AhwGK8pLbbX+9Eioaxg8jtAuHu8IyLmAYtzzOu/Q9PRNGhYEc= X-Received: from pjbph15.prod.google.com ([2002:a17:90b:3bcf:b0:32d:df7e:66c2]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:4b03:b0:251:3d1c:81f4 with SMTP id d9443c01a7336-26813cf3339mr29737275ad.54.1758113267744; Wed, 17 Sep 2025 05:47:47 -0700 (PDT) Date: Wed, 17 Sep 2025 05:47:45 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250912232319.429659-1-seanjc@google.com> <20250912232319.429659-10-seanjc@google.com> Message-ID: Subject: Re: [PATCH v15 09/41] KVM: x86: Load guest FPU state when access XSAVE-managed MSRs From: Sean Christopherson To: Binbin Wu Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Mathias Krause , John Allen , Rick Edgecombe , Chao Gao , Maxim Levitsky , Xiaoyao Li , Zhang Yi Z Content-Type: text/plain; charset="us-ascii" On Tue, Sep 16, 2025, Binbin Wu wrote: > > +/* > > + * Lock and/or reload guest FPU and access xstate MSRs. For accesses initiated > > > Lock is unconditional and reload is conditional. > "and/or" seems not accurate? Agreed. This? /* * Lock andr (re)load guest FPU and access xstate MSRs. For accesses initiated * by host, guest FPU is loaded in __msr_io(). For accesses initiated by guest, * guest FPU should have been loaded already. */ > > > + * by host, guest FPU is loaded in __msr_io(). For accesses initiated by guest, > > + * guest FPU should have been loaded already. > > + */ > > +static __always_inline void kvm_access_xstate_msr(struct kvm_vcpu *vcpu, > > + struct msr_data *msr_info, > > + int access) > > +{ > > + BUILD_BUG_ON(access != MSR_TYPE_R && access != MSR_TYPE_W); > > + > > + KVM_BUG_ON(!is_xstate_managed_msr(vcpu, msr_info->index), vcpu->kvm); > > + KVM_BUG_ON(!vcpu->arch.guest_fpu.fpstate->in_use, vcpu->kvm); > > + > > + kvm_fpu_get(); > > + if (access == MSR_TYPE_R) > > + rdmsrq(msr_info->index, msr_info->data); > > + else > > + wrmsrq(msr_info->index, msr_info->data); > > + kvm_fpu_put(); > > +} > > + > > +static __maybe_unused void kvm_set_xstate_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > +{ > > + kvm_access_xstate_msr(vcpu, msr_info, MSR_TYPE_W); > > +} > > + > > +static __maybe_unused void kvm_get_xstate_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > +{ > > + kvm_access_xstate_msr(vcpu, msr_info, MSR_TYPE_R); > > +} > > + > > int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > { > > u32 msr = msr_info->index; > > @@ -4551,11 +4614,25 @@ static int __msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs *msrs, > > int (*do_msr)(struct kvm_vcpu *vcpu, > > unsigned index, u64 *data)) > > { > > + bool fpu_loaded = false; > > int i; > > - for (i = 0; i < msrs->nmsrs; ++i) > > + for (i = 0; i < msrs->nmsrs; ++i) { > > + /* > > + * If userspace is accessing one or more XSTATE-managed MSRs, > > + * temporarily load the guest's FPU state so that the guest's > > + * MSR value(s) is resident in hardware, i.e. so that KVM can > > Using "i.e." and "so that" together feels repetitive.[...] /* * If userspace is accessing one or more XSTATE-managed MSRs, * temporarily load the guest's FPU state so that the guest's * MSR value(s) is resident in hardware and thus can be accessed * via RDMSR/WRMSR. */