On 08/09/15 07:03, Sam Bobroff wrote: > On Tue, Sep 01, 2015 at 12:53:26PM +0200, Thomas Huth wrote: >> On 01/09/15 02:38, David Gibson wrote: >>> On Mon, Aug 31, 2015 at 08:46:01PM +0200, Thomas Huth wrote: >>>> From: Michael Ellerman <mich...@ellerman.id.au> >>>> >>>> Some powerpc systems have support for a hardware random number generator >>>> (hwrng). If such a hwrng is present the host kernel can provide access >>>> to it via the H_RANDOM hcall. >>>> >>>> The kernel advertises the presence of a hwrng with the KVM_CAP_PPC_HWRNG >>>> capability. If this is detected we add the appropriate device tree bits >>>> to advertise the presence of the hwrng to the guest kernel. >>>> >>>> Signed-off-by: Michael Ellerman <mich...@ellerman.id.au> >>>> [thuth: Refreshed patch so it applies to QEMU master branch] >>>> Signed-off-by: Thomas Huth <th...@redhat.com> >>> >>> So, I'm confused by one thing. >>> >>> I thought new kernel handled hcalls were supposed to be disabled by >>> default, but I don't see any calls to kvmppc_enable_hcall() to turn on >>> H_RANDOM. >> >> Michael's patch was from 2013, the kvmppc_enable_hcall() stuff seems to >> be from 2014 ... so the enablement is likely missing in this patch, >> indeed. I didn't test the in-kernel hypercall yet, just my QEMU >> implementation so far, that's why I did not notice this yet. >> >> Michael, do you want to rework your patch? Or shall I add an additional >> enablement patch to my queue? > > If I recall correctly, it's specifically not enabled: there was quite a lot of > discussion about it when Michael posted the patches and I think the consensus > was that it should only be enabled by QEMU, and only if the user could decide > if it was used or not.
Can you find this discussion in a mailing list archive somewhere? The only discussions I've found are basically these: http://lists.nongnu.org/archive/html/qemu-devel/2013-09/msg04233.html https://lkml.org/lkml/fancy/2013/10/1/49 ... and there it was only discussed that the call should be implemented in QEMU, too. I did not spot any discussion about making it switchable for the user? Thomas
