From: 'Joerg Roedel' <joro@8bytes.org> To: David Laight <David.Laight@aculab.com> Cc: "x86@kernel.org" <x86@kernel.org>, Hyunwook Baek <baekhw@google.com>, Joerg Roedel <jroedel@suse.de>, "stable@vger.kernel.org" <stable@vger.kernel.org>, "hpa@zytor.com" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>, Dave Hansen <dave.hansen@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>, Jiri Slaby <jslaby@suse.cz>, Dan Williams <dan.j.williams@intel.com>, Tom Lendacky <thomas.lendacky@amd.com>, Juergen Gross <jgross@suse.com>, Kees Cook <keescook@chromium.org>, David Rientjes <rientjes@google.com>, Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>, Masami Hiramatsu <mhiramat@kernel.org>, Mike Stunes <mstunes@vmware.com>, Sean Christopherson <seanjc@google.com>, Martin Radev <martin.b.radev@gmail.com>, Arvind Sankar <nivedita@alum.mit.edu>, "linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "virtualization@lists.linux-foundation.org" <virtualization@lists.linux-foundation.org> Subject: Re: [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user Date: Wed, 12 May 2021 10:37:34 +0200 [thread overview] Message-ID: <YJuTzhSp2XAJIYlv@8bytes.org> (raw) In-Reply-To: <0496626f018d4d27a8034a4822170222@AcuMS.aculab.com> On Wed, May 12, 2021 at 08:04:33AM +0000, David Laight wrote: > That can't be right at all. > __put/get_user() are only valid on user addresses and will try to > fault in a missing page - so can sleep. Yes, in general these functions can sleep, but not in this context. They are called in atomic context and the page-fault handler will notice that and goes down the __bad_area_nosemaphore() path and only do the fixup. I also thought about adding page_fault_disable()/page_fault_enable() calls, but being in atomic context is enough according to the faulthandler_disabled() implementation. This is exactly what is needed here. All I want to know is whether a fault happened or not, the page-fault handler must not try to fix the fault in any way. If a fault happens it is later fixed up in vc_forward_exception(). > At best this is abused the calls. Yes, but that is only due to the naming of these functions. In this case they do exactly what is needed. Regards, Joerg
next prev parent reply other threads:[~2021-05-12 8:37 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-12 7:54 [PATCH 0/6] x86/sev-es: Fixes for SEV-ES guest support Joerg Roedel 2021-05-12 7:54 ` [PATCH 1/6] x86/sev-es: Don't return NULL from sev_es_get_ghcb() Joerg Roedel 2021-05-12 7:54 ` [PATCH 2/6] x86/sev-es: Forward page-faults which happen during emulation Joerg Roedel 2021-05-12 17:31 ` Sean Christopherson 2021-05-19 13:16 ` Joerg Roedel 2021-05-12 7:54 ` [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user Joerg Roedel 2021-05-12 8:04 ` David Laight 2021-05-12 8:16 ` Juergen Gross 2021-05-12 8:50 ` 'Joerg Roedel' 2021-05-12 8:58 ` Juergen Gross 2021-05-12 9:31 ` David Laight 2021-05-12 9:32 ` Joerg Roedel 2021-05-19 11:33 ` 'Joerg Roedel' 2021-05-12 8:37 ` 'Joerg Roedel' [this message] 2021-05-12 15:59 ` Dave Hansen 2021-05-12 15:57 ` Dave Hansen 2021-05-12 16:00 ` Joerg Roedel 2021-05-12 7:54 ` [PATCH 4/6] Revert "x86/sev-es: Handle string port IO to kernel memory properly" Joerg Roedel 2021-05-12 17:38 ` Sean Christopherson 2021-05-19 12:22 ` Joerg Roedel 2021-05-12 7:54 ` [PATCH 5/6] x86/sev-es: Fix error message in runtime #VC handler Joerg Roedel 2021-05-12 7:54 ` [PATCH 6/6] x86/sev-es: Leave NMI-mode before sending signals Joerg Roedel
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