Re: [Qemu-devel] [PATCH] ppc: fix ppc_set_compat() with KVM PR
On Tue, 15 Aug 2017 14:04:09 +1000 David Gibsonwrote: > On Mon, Aug 14, 2017 at 07:49:16PM +0200, Greg Kurz wrote: > > When running in KVM PR mode, kvmppc_set_compat() always fail because the > > current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now that > > the machine code inconditionally calls ppc_set_compat_all() at reset time > > to restore the compat mode default value (commit 66d5c492dd3a9), it is > > impossible to start a guest with PR: > > > > qemu-system-ppc64: Unable to set CPU compatibility mode in KVM: > > Invalid argument > > > > A tentative patch [1] was recently sent by Suraj to address the issue, but > > it would prevent the compat mode to be turned off on reset. And we really > > don't want to explicitely check for KVM PR. During the patch's review, > > David suggested that we should only call the KVM ioctl() if the compat > > PVR changes. This allows at least to run with KVM PR, provided no compat > > mode is requested from the command line (which should be the case when > > running PR nested). This is what this patch does. > > I'm not sure that's true any more, since we now prefer compat modes > during CAS. I guess we could exclude the compat modes from the Oops, I wanted to talk about CAS and I... forgot :( So, indeed, CAS fails to apply compat mode and immediately returns H_HARDWARE to the guest, ie the rest of CAS isn't done :-\. Linux guests print a warning: WARNING: ibm,client-architecture-support call FAILED! done and (luckily?) continue to boot anyway (at least that's what happens with RHEL7 guests). > advertised list based on what KVM supports, but that seems pretty > awkward. > I'll re-read the details in LoPAPR and try to come up with something. Cheers, -- Greg > > While here, we also fix the side effect where KVM would fail but we would > > change the CPU state in QEMU anyway. > > > > [1] http://patchwork.ozlabs.org/patch/782039/ > > > > Signed-off-by: Greg Kurz > > In any case, this makes things better than they were, so I'm applying. > > > --- > > target/ppc/compat.c |9 + > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/target/ppc/compat.c b/target/ppc/compat.c > > index f1b67faa97e3..f8729fe46d61 100644 > > --- a/target/ppc/compat.c > > +++ b/target/ppc/compat.c > > @@ -140,16 +140,17 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t > > compat_pvr, Error **errp) > > > > cpu_synchronize_state(CPU(cpu)); > > > > -cpu->compat_pvr = compat_pvr; > > -env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > > - > > -if (kvm_enabled()) { > > +if (kvm_enabled() && cpu->compat_pvr != compat_pvr) { > > int ret = kvmppc_set_compat(cpu, cpu->compat_pvr); > > if (ret < 0) { > > error_setg_errno(errp, -ret, > > "Unable to set CPU compatibility mode in > > KVM"); > > +return; > > } > > } > > + > > +cpu->compat_pvr = compat_pvr; > > +env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > > } > > > > typedef struct { > > > pgpYFhxJWm3lm.pgp Description: OpenPGP digital signature
Re: [Qemu-devel] [PATCH] ppc: fix ppc_set_compat() with KVM PR
On Tue, 15 Aug 2017 11:40:34 +1000 Suraj Jitindar Singhwrote: > On Mon, 2017-08-14 at 19:49 +0200, Greg Kurz wrote: > > When running in KVM PR mode, kvmppc_set_compat() always fail because > > the > > current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now > > that > > the machine code inconditionally calls ppc_set_compat_all() at reset > > time > > to restore the compat mode default value (commit 66d5c492dd3a9), it > > is > > impossible to start a guest with PR: > > > > qemu-system-ppc64: Unable to set CPU compatibility mode in KVM: > > Invalid argument > > > > A tentative patch [1] was recently sent by Suraj to address the > > issue, but > > it would prevent the compat mode to be turned off on reset. And we > > really > > don't want to explicitely check for KVM PR. During the patch's > > review, > > David suggested that we should only call the KVM ioctl() if the > > compat > > PVR changes. This allows at least to run with KVM PR, provided no > > compat > > mode is requested from the command line (which should be the case > > when > > running PR nested). This is what this patch does. > > > > While here, we also fix the side effect where KVM would fail but we > > would > > change the CPU state in QEMU anyway. > > > > [1] http://patchwork.ozlabs.org/patch/782039/ > > > > Signed-off-by: Greg Kurz > > I meant to send a follow up but it fell on my priority list so thanks > for this > No problem :) This is more a workaround than an actual fix since CAS will still want to change the compat mode and fail, but at least QEMU doesn't exit right away. I needed that to chase down another bug that breaks loadvm of a KVM PR guest. > Looks good to me > > Reviewed-by: Suraj Jitindar Singh > Thanks! > > --- > > target/ppc/compat.c |9 + > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/target/ppc/compat.c b/target/ppc/compat.c > > index f1b67faa97e3..f8729fe46d61 100644 > > --- a/target/ppc/compat.c > > +++ b/target/ppc/compat.c > > @@ -140,16 +140,17 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t > > compat_pvr, Error **errp) > > > > cpu_synchronize_state(CPU(cpu)); > > > > -cpu->compat_pvr = compat_pvr; > > -env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > > - > > -if (kvm_enabled()) { > > +if (kvm_enabled() && cpu->compat_pvr != compat_pvr) { > > int ret = kvmppc_set_compat(cpu, cpu->compat_pvr); > > if (ret < 0) { > > error_setg_errno(errp, -ret, > > "Unable to set CPU compatibility mode > > in KVM"); > > +return; > > } > > } > > + > > +cpu->compat_pvr = compat_pvr; > > +env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > > } > > > > typedef struct { > > pgpnggAhms9ep.pgp Description: OpenPGP digital signature
Re: [Qemu-devel] [PATCH] ppc: fix ppc_set_compat() with KVM PR
On Mon, Aug 14, 2017 at 07:49:16PM +0200, Greg Kurz wrote: > When running in KVM PR mode, kvmppc_set_compat() always fail because the > current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now that > the machine code inconditionally calls ppc_set_compat_all() at reset time > to restore the compat mode default value (commit 66d5c492dd3a9), it is > impossible to start a guest with PR: > > qemu-system-ppc64: Unable to set CPU compatibility mode in KVM: > Invalid argument > > A tentative patch [1] was recently sent by Suraj to address the issue, but > it would prevent the compat mode to be turned off on reset. And we really > don't want to explicitely check for KVM PR. During the patch's review, > David suggested that we should only call the KVM ioctl() if the compat > PVR changes. This allows at least to run with KVM PR, provided no compat > mode is requested from the command line (which should be the case when > running PR nested). This is what this patch does. I'm not sure that's true any more, since we now prefer compat modes during CAS. I guess we could exclude the compat modes from the advertised list based on what KVM supports, but that seems pretty awkward. > While here, we also fix the side effect where KVM would fail but we would > change the CPU state in QEMU anyway. > > [1] http://patchwork.ozlabs.org/patch/782039/ > > Signed-off-by: Greg KurzIn any case, this makes things better than they were, so I'm applying. > --- > target/ppc/compat.c |9 + > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/target/ppc/compat.c b/target/ppc/compat.c > index f1b67faa97e3..f8729fe46d61 100644 > --- a/target/ppc/compat.c > +++ b/target/ppc/compat.c > @@ -140,16 +140,17 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t > compat_pvr, Error **errp) > > cpu_synchronize_state(CPU(cpu)); > > -cpu->compat_pvr = compat_pvr; > -env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > - > -if (kvm_enabled()) { > +if (kvm_enabled() && cpu->compat_pvr != compat_pvr) { > int ret = kvmppc_set_compat(cpu, cpu->compat_pvr); > if (ret < 0) { > error_setg_errno(errp, -ret, > "Unable to set CPU compatibility mode in KVM"); > +return; > } > } > + > +cpu->compat_pvr = compat_pvr; > +env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > } > > typedef struct { > -- David Gibson| I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson signature.asc Description: PGP signature
Re: [Qemu-devel] [PATCH] ppc: fix ppc_set_compat() with KVM PR
On Mon, 2017-08-14 at 19:49 +0200, Greg Kurz wrote: > When running in KVM PR mode, kvmppc_set_compat() always fail because > the > current PR implementation doesn't handle KVM_REG_PPC_ARCH_COMPAT. Now > that > the machine code inconditionally calls ppc_set_compat_all() at reset > time > to restore the compat mode default value (commit 66d5c492dd3a9), it > is > impossible to start a guest with PR: > > qemu-system-ppc64: Unable to set CPU compatibility mode in KVM: > Invalid argument > > A tentative patch [1] was recently sent by Suraj to address the > issue, but > it would prevent the compat mode to be turned off on reset. And we > really > don't want to explicitely check for KVM PR. During the patch's > review, > David suggested that we should only call the KVM ioctl() if the > compat > PVR changes. This allows at least to run with KVM PR, provided no > compat > mode is requested from the command line (which should be the case > when > running PR nested). This is what this patch does. > > While here, we also fix the side effect where KVM would fail but we > would > change the CPU state in QEMU anyway. > > [1] http://patchwork.ozlabs.org/patch/782039/ > > Signed-off-by: Greg KurzI meant to send a follow up but it fell on my priority list so thanks for this Looks good to me Reviewed-by: Suraj Jitindar Singh > --- > target/ppc/compat.c |9 + > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/target/ppc/compat.c b/target/ppc/compat.c > index f1b67faa97e3..f8729fe46d61 100644 > --- a/target/ppc/compat.c > +++ b/target/ppc/compat.c > @@ -140,16 +140,17 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t > compat_pvr, Error **errp) > > cpu_synchronize_state(CPU(cpu)); > > -cpu->compat_pvr = compat_pvr; > -env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > - > -if (kvm_enabled()) { > +if (kvm_enabled() && cpu->compat_pvr != compat_pvr) { > int ret = kvmppc_set_compat(cpu, cpu->compat_pvr); > if (ret < 0) { > error_setg_errno(errp, -ret, > "Unable to set CPU compatibility mode > in KVM"); > +return; > } > } > + > +cpu->compat_pvr = compat_pvr; > +env->spr[SPR_PCR] = pcr & pcc->pcr_mask; > } > > typedef struct { >