From nobody Thu Oct 2 19:27:59 2025 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 B31022BF01E for ; Fri, 12 Sep 2025 23:23:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757719419; cv=none; b=QAJ1XuUwq3HP0qzmzrrXJJSwMHxBPMRMW97iQOAIYhPsJy8eYOGKV1/t88EaWfygDPrdqx4ujw/6aKu5PmS8FxxuihFQ1Z+KqGz4THLosQxhyoTRNtSKvTjKks0Y/5x24PJm7RD0GFDnN/2eSaMK1yarKkrnskKTR0fME25gVlY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757719419; c=relaxed/simple; bh=R/hsEZ3OEznvSmN6Xu/NmYJshewwUaH/QtJ9rZVe4y0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=lAwbHuj6N+b0RSURxwDtBxEjYsrt11iZEuxmBC0A1W8gPWMaz9ffL4gcP960Q0JOMw3X0TmZ3bCpaz1D88oT9N1E6v7DJtN2YlVh1NMkhJUw6tOI929jn33jVzdBuKoGvEYn1Ru3ZXyGUTULss1ZocVXxpR+gyIZElLMVkC1ZDs= 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=iVCTgE3F; arc=none smtp.client-ip=209.85.215.202 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="iVCTgE3F" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-b4d48818a04so1668626a12.1 for ; Fri, 12 Sep 2025 16:23:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1757719417; x=1758324217; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=4x8cFQ9I8IrL0w8PA5lioMQm1qn/X8VrzBwyUBJiKwk=; b=iVCTgE3FlSmFC9ZgtdmHpLzk3CA14ZaCuHajYKMOgVhLCAsRWHSBLcn52ocQeMhx91 dk1z42P0GEDb8GDoUzpvBnr3a6EnbUNYqC0B64er0HvBTnD7n4Y/iDB131kq3MnSk2t8 A9cfZ7zfvZ7wQKy2xtmLC2kWvpfRs+6nf4zp0vzZk9SFyzdFzgsiRM9TiTP5TRXTV6ap EuJCiOu6sE3OwpIsOHtiQKg+S4wczoNUHPIroBKzra7b+vXzo/mxVndsPCkDjcyMVQuR UOWJZNZH/55rt+L8z8Nd6fVwVuA3kgrkKkif46F8mYKdUKpzK7/DIM0cR8AZLgAL5oDO IZ3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757719417; x=1758324217; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=4x8cFQ9I8IrL0w8PA5lioMQm1qn/X8VrzBwyUBJiKwk=; b=mFBv+wdF6vw085JsTxlUaykNu6tLfHcZ/Czw7aS8Yqr2Yf9r+Zcfvv51krSjM/b5nb QupVVbV5AW8UsZjxjyBCkaljADPGj5WOhmZ4Qi2noEuT/lrvsziskOnJ9vwfAz0mT6Dq AaRUKgGQrLj8Mzrfl9XTehMLmY3qyrtf111JChrHAtOQLgc2GMZYlmDINTckL0aT2I8J m0xkxR2+1MIF1qjtMfHPd+eQ1xV+K66FGqaLr6p7rc+/Lah022LmJ7XS+qxLRJnf2MDW TtSFPow/DOeqzO0yndbY0GuSUdzSRrY0shkxtZEgQG8Rs79VLwf8s+XFaBcf35dF1fSt Asiw== X-Forwarded-Encrypted: i=1; AJvYcCVm6B7DqnhKNSc0iAw5NeJ/o32QC8HVmqfEpkM5qSK579VRaP2TFpeyiSani3x0bWtr0OTb0qcwhkn/by8=@vger.kernel.org X-Gm-Message-State: AOJu0YyY884u0v7svJ6XaL+UKB9Jfs7XCe1jwkG6gyXP/Kb+VAPtaW8f 3SZZAnx3xK5Or/GIJPtUPZntHaFGVOKYbI71wTFHoigbj10R0Kg6tFj4iDi3J3hXAr2vIVdsOC2 aYoK6Ng== X-Google-Smtp-Source: AGHT+IHL2nuJLf6q7uA5vbcBTUvwqLs20KOTZTeKNgV7CYzfjmBlfXMi0Vi99kCRqkOf1/zS/oAOJS5ZmwU= X-Received: from pjbqb3.prod.google.com ([2002:a17:90b:2803:b0:32b:8eda:24e8]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:6ba4:b0:251:e18:bcab with SMTP id adf61e73a8af0-2602c240dfcmr4538494637.38.1757719417056; Fri, 12 Sep 2025 16:23:37 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 12 Sep 2025 16:22:45 -0700 In-Reply-To: <20250912232319.429659-1-seanjc@google.com> 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> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250912232319.429659-8-seanjc@google.com> Subject: [PATCH v15 07/41] KVM: x86: Refresh CPUID on write to guest MSR_IA32_XSS From: Sean Christopherson To: Paolo Bonzini , Sean Christopherson Cc: 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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Yang Weijiang Update CPUID.(EAX=3D0DH,ECX=3D1).EBX to reflect current required xstate size due to XSS MSR modification. CPUID(EAX=3D0DH,ECX=3D1).EBX reports the required storage size of all enabl= ed xstate features in (XCR0 | IA32_XSS). The CPUID value can be used by guest before allocate sufficient xsave buffer. Note, KVM does not yet support any XSS based features, i.e. supported_xss is guaranteed to be zero at this time. Opportunistically skip CPUID updates if XSS value doesn't change. Suggested-by: Sean Christopherson Co-developed-by: Zhang Yi Z Signed-off-by: Zhang Yi Z Signed-off-by: Yang Weijiang Reviewed-by: Maxim Levitsky Reviewed-by: Chao Gao Reviewed-by: Xiaoyao Li Tested-by: Mathias Krause Tested-by: John Allen Tested-by: Rick Edgecombe Signed-off-by: Chao Gao Signed-off-by: Sean Christopherson Reviewed-by: Binbin Wu --- arch/x86/kvm/cpuid.c | 3 ++- arch/x86/kvm/x86.c | 2 ++ 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 46cf616663e6..b5f87254ced7 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -316,7 +316,8 @@ static void kvm_update_cpuid_runtime(struct kvm_vcpu *v= cpu) best =3D kvm_find_cpuid_entry_index(vcpu, 0xD, 1); if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) || cpuid_entry_has(best, X86_FEATURE_XSAVEC))) - best->ebx =3D xstate_required_size(vcpu->arch.xcr0, true); + best->ebx =3D xstate_required_size(vcpu->arch.xcr0 | + vcpu->arch.ia32_xss, true); } =20 static bool kvm_cpuid_has_hyperv(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5a5af40c06a9..519d58b82f7f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3993,6 +3993,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct = msr_data *msr_info) */ if (data & ~vcpu->arch.guest_supported_xss) return 1; + if (vcpu->arch.ia32_xss =3D=3D data) + break; vcpu->arch.ia32_xss =3D data; vcpu->arch.cpuid_dynamic_bits_dirty =3D true; break; --=20 2.51.0.384.g4c02a37b29-goog