[RFC PATCH kernel] KVM: PPC: Book3S PR: Fix WIMG handling under pHyp

[Alexander Graf]

On 22.11.17 04:42, Alexey Kardashevskiy wrote:
> 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG
> bits preserving but it missed 2 special cases:
> - a magic page in kvmppc_mmu_book3s_64_xlate() and
> - guest real mode in kvmppc_handle_pagefault().
> 
> For these ptes WIMG were 0 and pHyp failed on these causing a guest to
> stop in the very beginning at NIP=0x100 (due to bd9166ffe
> "KVM: PPC: Book3S PR: Exit KVM on failed mapping").
> 
> This initializes WIMG to non-zero value HPTE_R_M. The value is chosen
> as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from
> kvmppc_mmu_map_page().
> 
> Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits"
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
> 
> This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M
> is arguable.

This does indeed fix the breakage we've seen:

Tested-by: Ruediger Oertel <ro at suse.de>


Alex