From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCH v5 1/4] xen/libxc: Allow changes to hypervisor CPUID leaf from config file Date: Wed, 19 Mar 2014 11:44:40 +0000 Message-ID: <532991380200007800125A97@nat28.tlf.novell.com> References: <1395190714-3802-1-git-send-email-boris.ostrovsky@oracle.com> <1395190714-3802-2-git-send-email-boris.ostrovsky@oracle.com> <1395221220.10203.8.camel@kazak.uk.xensource.com> <532972460200007800125962@nat28.tlf.novell.com> <1395222742.10203.29.camel@kazak.uk.xensource.com> <53297A5002000078001259DC@nat28.tlf.novell.com> <1395225598.10203.49.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1395225598.10203.49.camel@kazak.uk.xensource.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: keir@xen.org, eddie.dong@intel.com, stefano.stabellini@eu.citrix.com, andrew.cooper3@citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, jun.nakajima@intel.com, yang.z.zhang@intel.com, Boris Ostrovsky List-Id: xen-devel@lists.xenproject.org >>> On 19.03.14 at 11:39, Ian Campbell wrote: > On Wed, 2014-03-19 at 10:06 +0000, Jan Beulich wrote: >> >>> On 19.03.14 at 10:52, Ian Campbell wrote: >> > On Wed, 2014-03-19 at 09:32 +0000, Jan Beulich wrote: >> >> >>> On 19.03.14 at 10:27, Ian Campbell wrote: >> >> > On Tue, 2014-03-18 at 20:58 -0400, Boris Ostrovsky wrote: >> >> >> Currently only "real" cpuid leaves can be overwritten by users via >> >> >> 'cpuid' option in the configuration file. This patch provides ability to >> >> >> do the same for hypervisor leaves (but for now only 0x40000000 is > allowed). >> >> >> >> >> >> Signed-off-by: Boris Ostrovsky >> >> >> --- >> >> >> tools/libxc/xc_cpuid_x86.c | 71 >> >> > ++++++++++++++++++++++++++++++++++++++++-- >> >> >> xen/arch/x86/domain.c | 19 +++++++++-- >> >> >> xen/arch/x86/traps.c | 3 ++ >> >> >> xen/include/asm-x86/domain.h | 7 +++++ >> >> >> 4 files changed, 95 insertions(+), 5 deletions(-) >> >> >> >> >> >> diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c >> >> >> index bbbf9b8..5501d5b 100644 >> >> >> --- a/tools/libxc/xc_cpuid_x86.c >> >> >> +++ b/tools/libxc/xc_cpuid_x86.c >> >> >> @@ -33,6 +33,8 @@ >> >> >> #define DEF_MAX_INTELEXT 0x80000008u >> >> >> #define DEF_MAX_AMDEXT 0x8000001cu >> >> >> >> >> >> +#define IS_HYPERVISOR_LEAF(idx) (((idx) & 0xffff0000) == 0x40000000) >> >> > >> >> > Not idx == 0x40000000? >> >> > >> >> > Also as I think Jan said before if viridian support is enabled then the >> >> > Xen leaves may be elsewhere (at 0x100 increments above that address >> >> > IIRC). >> >> >> >> But that's exactly why the low 16 bits should be masked off in >> >> above comparison. >> > >> > Is it 0x100 or 0x1000 increments? I thought it was 0x100, in which case >> > shouldn't the mask be 0xfffff000? >> >> It's 0x100 increments, but that doesn't relate to the mask to be >> applied here - major groups appear to be using 64k increments >> (0000 - basic, 4000 - hypervisor, 8000 - extended, 8086 - >> Transmeta, C000 - VIA/Cyrix, and I guess there are others I >> don't know about). I don't think I've seen this publicly/formally >> documented so far. > > OK, that makes sense from a major group perspective. > > But I think the "first minor group" of hypervisor nodes at 0x40000000 > stops at 0x40010000, at least implicitly due to the existing code in e.g > unmodified_drivers/linux-2.6/platform-pci/platform-pci.c and > tools/misc/xen-detect.c. I don't think it is out of the question that we > might want to put other stuff at e.g. 0x40020000 (or at least we should > retain the option). So that means you advocate for shrinking the number of significant bits checked for. Question then is by how much - perhaps we should then consider the whole range 40000000-7FFFFFFF as hypervisor reserved? Jan