linux-kernel - Re: [Xen-devel] [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 4 Apr 2016 09:40:51 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	David Vrabel <david.vrabel@...rix.com>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	KVM list <kvm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	xen-devel <Xen-devel@...ts.xen.org>,
	Borislav Petkov <bp@...en8.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [Xen-devel] [PATCH v5 7/9] x86/paravirt: Add paravirt_{read, write}_msr

On Mon, Apr 4, 2016 at 9:33 AM, David Vrabel <david.vrabel@...rix.com> wrote:
> On 02/04/16 15:01, Andy Lutomirski wrote:
>> This adds paravirt hooks for unsafe MSR access.  On native, they
>> call native_{read,write}_msr.  On Xen, they use
>> xen_{read,write}_msr_safe.
>>
>> Nothing uses them yet for ease of bisection.  The next patch will
>> use them in rdmsrl, wrmsrl, etc.
>>
>> I intentionally didn't make them warn on #GP on Xen.  I think that
>> should be done separately by the Xen maintainers.
> ...
>> --- a/arch/x86/xen/enlighten.c
>> +++ b/arch/x86/xen/enlighten.c
>
> Reviewed-by: David Vrabel <david.vrabel@...rix.com>
>
>> @@ -1092,6 +1092,26 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
>>       return ret;
>>  }
>>
>> +static u64 xen_read_msr(unsigned int msr)
>> +{
>> +     /*
>> +      * This will silently swallow a #GP from RDMSR.  It may be worth
>> +      * changing that.
>
> This probably isn't important.
>

It might be nice to do a WARN_ON_ONCE like this series does for the
native case to help shake out latent bugs.

--Andy