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Re: [Qemu-ppc] [PATCH 2/2] target-ppc: KVM: Fix some kernel version edge


From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH 2/2] target-ppc: KVM: Fix some kernel version edge cases for kvmppc_reset_htab()
Date: Thu, 20 Sep 2012 10:58:20 +0200

On 20.09.2012, at 09:08, David Gibson wrote:

> The kvmppc_reset_htab() function invokes the KVM_PPC_ALLOCATE_HTAB vm ioctl
> to request KVM to allocate and reset a hash page table for the guest - it
> returns the size of hash table allocated, or 0 to indicate that qemu needs
> to allocate the hash table itself.  In practice qemu needs to allocate the
> htab for full emulation and with Book3sPR KVM, but the kernel has to
> allocate it for Book3sHV KVM (the hash table needs to be physically
> contiguous in that case).
> 
> Unfortunately, the logic in this function is incorrect for some existing
> kernels.  Specifically:
>  * at least some PR KVM versions advertise the relevant capability but
> don't actually implement the ioctl(), returning ENOTTY.
>  * For old kernels which don't have the capability, we currently return 0.
> This is correct for PV KVM, where we need to allocate the htab, but not for
> HV KVM - kernels of this era always allocate a 16MB hash table per guest.
> 
> This patch corrects both of these edge cases.
> 
> Signed-off-by: David Gibson <address@hidden>

Thanks, applied to ppc-next.


Alex




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