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([172.25.112.68]) by fmsmga001.fm.intel.com with ESMTP; 31 Jul 2023 00:02:04 -0700 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 2d8364a7-2f70-11ee-b254-6b7b168915f2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1690786934; x=1722322934; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=sycVsd87zmfA3yJCdcgOgrxd4mm6nSq5VT1UdIRGngQ=; b=ezfaFIjsoAjRlZeP5ypMnjJEjXCe45dxgAgZ0oIizMTfTKHPYroBeVKW sZIp4OrCMHILpMcY1s4UUd0LHsqps1y8Ruif7U86H85g7aVePo0PE3qeO YoKqGWTcb1ddawS/IUe53j4AS1g17zeu56qKDiYyl32HkERak2BINu4Ro viylJPuG9lzsNkG37OcVSOJCcsIeJogVJ8iMNCvHWXLVubIxSZBlRBoQX 5DUF/hwKJXeCLPPMgNOqMbY5XmNOpiALvRrcSCKtgpYiGBNijU5OYU44M 7BOCa1MB7BXbmoi7I8lFb1QeVX1vkokNe2y3yNB6MiZZ3ibJfeWm1AUll Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10787"; a="371649065" X-IronPort-AV: E=Sophos;i="6.01,244,1684825200"; d="scan'208";a="371649065" X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.01,202,1684825200"; d="scan'208";a="871543425" From: Xin Li To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org Cc: Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Andy Lutomirski , Oleg Nesterov , Tony Luck , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Sean Christopherson , Peter Zijlstra , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Josh Poimboeuf , "Paul E . McKenney" , Catalin Marinas , Randy Dunlap , Steven Rostedt , Kim Phillips , Xin Li , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Liam R . Howlett" , Sebastian Reichel , "Kirill A . Shutemov" , Suren Baghdasaryan , Pawan Gupta , Jiaxi Chen , Babu Moger , Jim Mattson , Sandipan Das , Lai Jiangshan , Hans de Goede , Reinette Chatre , Daniel Sneddon , Breno Leitao , Nikunj A Dadhania , Brian Gerst , Sami Tolvanen , Alexander Potapenko , Andrew Morton , Arnd Bergmann , "Eric W . Biederman" , Kees Cook , Masami Hiramatsu , Masahiro Yamada , Ze Gao , Fei Li , Conghui , Ashok Raj , "Jason A . Donenfeld" , Mark Rutland , Jacob Pan , Jiapeng Chong , Jane Malalane , David Woodhouse , Boris Ostrovsky , Arnaldo Carvalho de Melo , Yantengsi , Christophe Leroy , Sathvika Vasireddy Subject: [PATCH v9 14/36] x86/fred: Disallow the swapgs instruction when FRED is enabled Date: Sun, 30 Jul 2023 23:32:55 -0700 Message-Id: <20230731063317.3720-15-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230731063317.3720-1-xin3.li@intel.com> References: <20230731063317.3720-1-xin3.li@intel.com> MIME-Version: 1.0 From: "H. Peter Anvin (Intel)" The FRED architecture establishes the full supervisor/user through: 1) FRED event delivery from ring 3 swaps the value of the GS base address and that of the IA32_KERNEL_GS_BASE MSR. 2) ERETU swaps the value of the GS base address and that of the IA32_KERNEL_GS_BASE MSR. 3) LKGS is already upstreamed and automatically enabled with FRED to load the GS base address directly into the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s descriptor cache. As a result, there is no need to SWAPGS away from the kernel GS base, i.e., the swapgs instruction is no longer needed when FRED is enabled, thus is disallowed. Otherwise it causes #UD. Signed-off-by: H. Peter Anvin (Intel) Tested-by: Shan Kang Signed-off-by: Xin Li --- Changes since v8: * Explain why writing directly to the IA32_KERNEL_GS_BASE MSR is doing the right thing (Thomas Gleixner). --- arch/x86/kernel/process_64.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 265ab8fcb146..6d5fed29f552 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -166,7 +166,8 @@ static noinstr unsigned long __rdgsbase_inactive(void) lockdep_assert_irqs_disabled(); - if (!cpu_feature_enabled(X86_FEATURE_XENPV)) { + if (!cpu_feature_enabled(X86_FEATURE_FRED) && + !cpu_feature_enabled(X86_FEATURE_XENPV)) { native_swapgs(); gsbase = rdgsbase(); native_swapgs(); @@ -191,7 +192,8 @@ static noinstr void __wrgsbase_inactive(unsigned long gsbase) { lockdep_assert_irqs_disabled(); - if (!cpu_feature_enabled(X86_FEATURE_XENPV)) { + if (!cpu_feature_enabled(X86_FEATURE_FRED) && + !cpu_feature_enabled(X86_FEATURE_XENPV)) { native_swapgs(); wrgsbase(gsbase); native_swapgs();