From: 'Joerg Roedel' <joro@8bytes.org>
To: Joerg Roedel <jroedel@suse.de>
Cc: Juergen Gross <jgross@suse.com>,
David Laight <David.Laight@aculab.com>,
"x86@kernel.org" <x86@kernel.org>,
Hyunwook Baek <baekhw@google.com>,
"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>,
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, 19 May 2021 13:33:46 +0200 [thread overview]
Message-ID: <YKT3mpYlPqNHo1QU@8bytes.org> (raw)
In-Reply-To: <YJugs0CdiNo0/Gbd@suse.de>
On Wed, May 12, 2021 at 11:32:35AM +0200, Joerg Roedel wrote:
> On Wed, May 12, 2021 at 10:58:20AM +0200, Juergen Gross wrote:
> > No, those were used before, but commit 9da3f2b7405440 broke Xen's use
> > case. That is why I did commit 1457d8cf7664f.
>
> [...]
>
> Having the distinction between user and kernel memory accesses
> explicitly in the code seems to be the most robust solution.
On the other hand, as I found out today, 9da3f2b7405440 had a short
life-time and got reverted upstream. So using __get_user()/__put_user()
should be fine in this code path. It just deserves a comment explaining
its use here and why pagefault_enable()/disable() is not needed.
Even the get_kernel* helpers use __get_user_size() internally.
Regards,
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: 'Joerg Roedel' <joro@8bytes.org>
To: Joerg Roedel <jroedel@suse.de>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"virtualization@lists.linux-foundation.org"
<virtualization@lists.linux-foundation.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
"hpa@zytor.com" <hpa@zytor.com>, Jiri Slaby <jslaby@suse.cz>,
"x86@kernel.org" <x86@kernel.org>,
David Rientjes <rientjes@google.com>,
Martin Radev <martin.b.radev@gmail.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Kees Cook <keescook@chromium.org>, Cfir Cohen <cfir@google.com>,
Hyunwook Baek <baekhw@google.com>,
"linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
Andy Lutomirski <luto@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Juergen Gross <jgross@suse.com>, Mike Stunes <mstunes@vmware.com>,
Sean Christopherson <seanjc@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
David Laight <David.Laight@aculab.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Erdem Aktas <erdemaktas@google.com>
Subject: Re: [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user
Date: Wed, 19 May 2021 13:33:46 +0200 [thread overview]
Message-ID: <YKT3mpYlPqNHo1QU@8bytes.org> (raw)
In-Reply-To: <YJugs0CdiNo0/Gbd@suse.de>
On Wed, May 12, 2021 at 11:32:35AM +0200, Joerg Roedel wrote:
> On Wed, May 12, 2021 at 10:58:20AM +0200, Juergen Gross wrote:
> > No, those were used before, but commit 9da3f2b7405440 broke Xen's use
> > case. That is why I did commit 1457d8cf7664f.
>
> [...]
>
> Having the distinction between user and kernel memory accesses
> explicitly in the code seems to be the most robust solution.
On the other hand, as I found out today, 9da3f2b7405440 had a short
life-time and got reverted upstream. So using __get_user()/__put_user()
should be fine in this code path. It just deserves a comment explaining
its use here and why pagefault_enable()/disable() is not needed.
Even the get_kernel* helpers use __get_user_size() internally.
Regards,
Joerg
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-05-19 11:33 UTC|newest]
Thread overview: 42+ 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 ` 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 ` 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 7:54 ` Joerg Roedel
2021-05-12 17:31 ` Sean Christopherson
2021-05-19 13:16 ` Joerg Roedel
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 7:54 ` Joerg Roedel
2021-05-12 8:04 ` David Laight
2021-05-12 8:04 ` David Laight
2021-05-12 8:16 ` Juergen Gross
2021-05-12 8:16 ` Juergen Gross via Virtualization
2021-05-12 8:50 ` 'Joerg Roedel'
2021-05-12 8:50 ` 'Joerg Roedel'
2021-05-12 8:58 ` Juergen Gross
2021-05-12 8:58 ` Juergen Gross via Virtualization
2021-05-12 9:31 ` David Laight
2021-05-12 9:31 ` David Laight
2021-05-12 9:32 ` Joerg Roedel
2021-05-12 9:32 ` Joerg Roedel
2021-05-19 11:33 ` 'Joerg Roedel' [this message]
2021-05-19 11:33 ` 'Joerg Roedel'
2021-05-12 8:37 ` 'Joerg Roedel'
2021-05-12 8:37 ` 'Joerg Roedel'
2021-05-12 15:59 ` Dave Hansen
2021-05-12 15:59 ` Dave Hansen
2021-05-12 15:57 ` Dave Hansen
2021-05-12 15:57 ` Dave Hansen
2021-05-12 16:00 ` Joerg Roedel
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 7:54 ` Joerg Roedel
2021-05-12 17:38 ` Sean Christopherson
2021-05-19 12:22 ` Joerg Roedel
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 ` Joerg Roedel
2021-05-12 7:54 ` [PATCH 6/6] x86/sev-es: Leave NMI-mode before sending signals Joerg Roedel
2021-05-12 7:54 ` Joerg Roedel
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