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From: David Laight <David.Laight@ACULAB.COM>
To: 'Juergen Gross' <jgross@suse.com>, 'Joerg Roedel' <joro@8bytes.org>
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>,
	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 09:31:10 +0000	[thread overview]
Message-ID: <8cdbb6928c7144c6b065c3ff68f03aee@AcuMS.aculab.com> (raw)
In-Reply-To: <92244e37-4443-98bd-24aa-bf59548aab47@suse.com>

From: Juergen Gross
> Sent: 12 May 2021 09:58
> 
> On 12.05.21 10:50, 'Joerg Roedel' wrote:
> > On Wed, May 12, 2021 at 10:16:12AM +0200, Juergen Gross wrote:
> >> You want something like xen_safe_[read|write]_ulong().
> >
> >  From a first glance I can't see it, what is the difference between the
> > xen_safe_*_ulong() functions and __get_user()/__put_user()? The only
> > difference I can see is that __get/__put_user() support different access
> > sizes, but neither of those disables page-faults by itself, for example.
> >
> > Couldn't these xen-specific functions not also be replaces by
> > __get_user()/__put_user()?
> 
> No, those were used before, but commit 9da3f2b7405440 broke Xen's use
> case. That is why I did commit 1457d8cf7664f.

I've just looked at 9da3f2b7405440.

It doesn't look right to me - wrong return value for a lot of cases.
OTOH it isn't in my newest tree at all.

If bogus_uaccess() is now elsewhere I can't see how (without changes)
it would allow through these faults.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight@ACULAB.COM>
To: 'Juergen Gross' <jgross@suse.com>, 'Joerg Roedel' <joro@8bytes.org>
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>,
	Joerg Roedel <jroedel@suse.de>, 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>,
	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>,
	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, 12 May 2021 09:31:10 +0000	[thread overview]
Message-ID: <8cdbb6928c7144c6b065c3ff68f03aee@AcuMS.aculab.com> (raw)
In-Reply-To: <92244e37-4443-98bd-24aa-bf59548aab47@suse.com>

From: Juergen Gross
> Sent: 12 May 2021 09:58
> 
> On 12.05.21 10:50, 'Joerg Roedel' wrote:
> > On Wed, May 12, 2021 at 10:16:12AM +0200, Juergen Gross wrote:
> >> You want something like xen_safe_[read|write]_ulong().
> >
> >  From a first glance I can't see it, what is the difference between the
> > xen_safe_*_ulong() functions and __get_user()/__put_user()? The only
> > difference I can see is that __get/__put_user() support different access
> > sizes, but neither of those disables page-faults by itself, for example.
> >
> > Couldn't these xen-specific functions not also be replaces by
> > __get_user()/__put_user()?
> 
> No, those were used before, but commit 9da3f2b7405440 broke Xen's use
> case. That is why I did commit 1457d8cf7664f.

I've just looked at 9da3f2b7405440.

It doesn't look right to me - wrong return value for a lot of cases.
OTOH it isn't in my newest tree at all.

If bogus_uaccess() is now elsewhere I can't see how (without changes)
it would allow through these faults.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  reply	other threads:[~2021-05-12  9:31 UTC|newest]

Thread overview: 51+ 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  8:04     ` David Laight
2021-05-12  8:16     ` Juergen Gross
2021-05-12  8:16       ` Juergen Gross via Virtualization
2021-05-12  8:16       ` Juergen Gross
2021-05-12  8:50       ` 'Joerg Roedel'
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  8:58           ` Juergen Gross
2021-05-12  9:31           ` David Laight [this message]
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
2021-05-12  9:32             ` Joerg Roedel
2021-05-19 11:33             ` 'Joerg Roedel'
2021-05-19 11:33               ` 'Joerg Roedel'
2021-05-19 11:33               ` 'Joerg Roedel'
2021-05-12  8:37     ` '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 15:59         ` 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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