On Thu, Jun 16, 2016 at 08:01:55PM +0530, Aneesh Kumar K.V wrote:
> "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com> writes:
>
> > "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com> writes:
> >
> >> "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com> writes:
> >>
> >>> "Darrick J. Wong" <darrick.w...@oracle.com> writes:
> >>>
> >>>> On Thu, Jun 16, 2016 at 03:23:47PM +1000, Michael Ellerman wrote:
> >>>>> On Wed, 2016-06-15 at 21:33 -0700, Darrick J. Wong wrote:
> >>>>>
> >>>>> > Hi Aneesh,
> >>>>> >
> >>>>> > I noticed when trying out 4.7-rc3 on qemu-2.5 that the kernel no
> >>>>> > longer
> >>>>> > boots. 4.6 booted just fine, so I bisected the kernel to the commit
> >>>>> > 30bda41aba4efb2370c97e2cbe7385de93ccc372, which is "powerpc/mm: Drop
> >>>>> > WIMG in
> >>>>> > favour of new constants". The changelog suggests that the KVM
> >>>>> > changes need
> >>>>> > closer review, and here's an actual crash:
> >>>>> >
> >>>>> > (I can send libvirt's machine xml, .config, and full dmesg if that
> >>>>> > helps.)
> >>>>>
> >>>>> Yes please.
> >>>>>
> >>>>> I'm successfully booting 4.7-rc's on qemu (2.5.0 (Debian
> >>>>> 1:2.5+dfsg-5ubuntu10.1)).
> >>>>
> >>>> Ok, see attached. I also sent along the dpkg --status output for qemu
> >>>> and qemu-slof; looks like we're running the same Ubuntu packages...
> >>>>
> >>>> ...my host kernel is 4.6.0 on x64.
> >>>
> >>> So this is Qemu TCG mode right ? I will try some test and update later.
> >>>
> >>
> >> I am able to reproduce this with
> >>
> >> qemu-system-ppc64 -kernel vmlinux -machine
> >> type=pseries,usb=off -smp 1 -m 1G -vga none -nographic -device
> >> usb-ehci -device usb-kbd -device usb-mouse
> >>
> >> Looks like enabling usb device is the issue.
> >>
> >
> > Hmm Qemu does
> >
> > /* Looks like an IO address */
> > /* FIXME: What WIMG combinations could be sensible for IO?
> > * For now we allow WIMG=010x, but are there others? */
> > /* FIXME: Should we check against registered IO addresses? */
> > if ((ptel & (HPTE64_R_W | HPTE64_R_I | HPTE64_R_M)) != HPTE64_R_I) {
> > return H_PARAMETER;
> > }
> >
>
>
> Can you try this patch ?
>
> Ben,
>
> The pHyp part of the comment was added by you in
> 3c726f8dee6f55e96475574e9f645327e461884c ([PATCH] ppc64: support 64k
> page) really an old commit. I also remember we having the discussion and
> concluding that it should be safe to assume that we can always enable
> memory coherence. Should we do the below patch of get Qemu fixed up ?
> like below
>
> - if ((ptel & (HPTE64_R_W | HPTE64_R_I | HPTE64_R_M)) != HPTE64_R_I) {
> + wimg_flags = (ptel & (HPTE64_R_W | HPTE64_R_I | HPTE64_R_M));
> +
> + if (wimg_flags != HPTE64_R_I && wimg_flags != (HPTE64_R_I |
> HPTE64_R_M)) {
> return H_PARAMETER;
> }
>
>
> commit 58f32706f64ee8fe21bbd7d6c211720cedec1292
> Author: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> Date: Thu Jun 16 19:43:39 2016 +0530
>
> powerpc/mm/hash: Don't add memory coherence if cache inhibited is set
>
> H_ENTER hcall handling in qemu had assumptions that a cache inhibited
> hpte entry won't have memory conference set. Also older kernel
coherence ? ^^^^^^^^^^
> mentioned that some version of pHyp required this (look at the comment
> removed by the commit mentioned below).
>
> Fixes: commit 30bda41aba4e("powerpc/mm: Drop WIMG in favour of new
> constant")
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
>
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index fcf676f7f522..89c2791bc510 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -201,9 +201,8 @@ unsigned long htab_convert_pte_flags(unsigned long
> pteflags)
> /*
> * We can't allow hardware to update hpte bits. Hence always
> * set 'R' bit and set 'C' if it is a write fault
> - * Memory coherence is always enabled
> */
> - rflags |= HPTE_R_R | HPTE_R_M;
> + rflags |= HPTE_R_R;
>
> if (pteflags & _PAGE_DIRTY)
> rflags |= HPTE_R_C;
> @@ -216,7 +215,12 @@ unsigned long htab_convert_pte_flags(unsigned long
> pteflags)
> if ((pteflags & _PAGE_CACHE_CTL ) == _PAGE_NON_IDEMPOTENT)
> rflags |= (HPTE_R_I | HPTE_R_G);
> if ((pteflags & _PAGE_CACHE_CTL) == _PAGE_SAO)
> - rflags |= (HPTE_R_I | HPTE_R_W);
> + rflags |= (HPTE_R_W | HPTE_R_I | HPTE_R_M);
> + /*
> + * Add memory coherence if cache inhibited is not set
> + */
> + if (!(rflags & HPTE_R_I))
> + rflags |= HPTE_R_M;
>
> return rflags;
> }
>
In any case, the VM boots again, thank you!
--D
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