> -----Original Message----- > From: Wood Scott-B07421 > Sent: Monday, February 07, 2011 12:52 PM > To: Alexander Graf > Cc: Yoder Stuart-B08248; Wood Scott-B07421; kvm-ppc@xxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx > Subject: Re: RFC: New API for PPC for vcpu mmu access > > On Mon, 7 Feb 2011 17:49:51 +0100 > Alexander Graf <agraf@xxxxxxx> wrote: > > > > > On 07.02.2011, at 17:40, Yoder Stuart-B08248 wrote: > > > > > Suggested change to this would be to have Qemu set tlb_type as > > > an _input_ argument. If KVM supports it, that type gets used, > > > else an error is returned. This would allow Qemu to tell > > > the kernel what type of MMU it is prepared to support. Without > > > this Qemu would just have to error out if the type returned is > > > unknown. > > > > Yes, we could use the same struct for get and set. On set, it could > transfer the mmu type, on get it could tell userspace the mmu type. > > What happens if a get is done before the first set, and there are multiple > MMU type options for this hardware, with differing entry sizes? > > Qemu would have to know beforehand how large to make the buffer. > > We could say that going forward, it's expected that qemu will do a TLB set > (either a full one, or a lightweight alternative) after creating a vcpu. > For compatibility, if this doesn't happen before the vcpu is run, the TLB > is created and initialized as it is today, but no new Qemu-visible features > will be enabled that way. Since I think the normal thing Qemu would want to do is determine the type/size before allocating space for the TLB, we could just pass in NULL for tlb_data on the first set. If tlb_data is NULL we just set the MMU type and return the size (and type). > If Qemu does a get without ever doing some set operation, it should get an > error, since the requirement to do a set is added at the same time as the > get API. Right. Stuart -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
