Re: [PATCH 3/3] KVM: PPC: Book3S: Add support for hwrng found on some powernv systems
From: Gleb Natapov <hidden>
Date: 2013-10-01 09:59:28
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On Tue, Oct 01, 2013 at 07:23:20PM +1000, Paul Mackerras wrote:
On Tue, Oct 01, 2013 at 11:39:08AM +0300, Gleb Natapov wrote:quoted
On Tue, Oct 01, 2013 at 06:34:26PM +1000, Michael Ellerman wrote:quoted
On Thu, Sep 26, 2013 at 11:06:59AM +0200, Paolo Bonzini wrote:quoted
Il 26/09/2013 08:31, Michael Ellerman ha scritto:quoted
Some powernv systems include a hwrng. Guests can access it via the H_RANDOM hcall.Is there any reason to do this in the kernel?It's less code, and it's faster :)quoted
It does not have to be a particularly fast path;Sure, but do we have to make it slow on purpose?We do not put non performance critical devices into the kernel.It's not a device, it's a single hypercall, specified by PAPR, which is the moral equivalent of x86's RDRAND.
OK. A couple of general questions. How guest knows when this hypercall is available? Is QEMU enable it when KVM_CAP_PPC_HWRNG is available (I haven't seen userspace patch that uses KVM_CAP_PPC_HWRNG)? What about QEMU TCG does it implement this hypercall or it emulates hwrng directly? -- Gleb.