| Message ID | 20200911043123.204162-1-farosas@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | spapr: Handle HPT allocation failure in nested guest | expand |
On Fri, 11 Sep 2020 01:31:23 -0300 Fabiano Rosas <farosas@linux.ibm.com> wrote: > The nested KVM code does not yet support HPT guests. Calling the > KVM_CAP_PPC_ALLOC_HTAB ioctl currently leads to KVM setting the guest > as HPT and erroneously executing code in L1 that should only run in > hypervisor mode, leading to an exception in the L1 vcpu thread when it > enters the nested guest. > > This can be reproduced with -machine max-cpu-compat=power8 in the L2 > guest command line. > > The KVM code has since been modified to fail the ioctl when running in Well, this isn't technically true for now. The KVM patch hasn't been merged yet, but I guess it's okay to merge the QEMU patch anyway since it shouldn't break older KVMs. > a nested environment so QEMU needs to be able to handle that. This > patch provides an error message informing the user about the lack of > support for HPT in nested guests. > > Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com> > --- > hw/ppc/spapr.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 9bce1892b5..ea2c755310 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1483,6 +1483,12 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, > spapr_free_hpt(spapr); > > rc = kvmppc_reset_htab(shift); > + > + if (rc == -EOPNOTSUPP) { As noted on the kvm-ppc list, from a POSIX standpoint it seems that ENOTSUP would be more appropriate... but since linux only knows about EOPNOTSUPP and it has an unrelated and poorly named ENOTSUPP, I guess it is okay to keep EOPNOTSUPP for the sake of consistency. Reviewed-by: Greg Kurz <groug@kaod.org> > + error_setg(errp, "HPT not supported in nested guests"); > + return; > + } > + > if (rc < 0) { > /* kernel-side HPT needed, but couldn't allocate one */ > error_setg_errno(errp, errno,
Fabiano Rosas <farosas@linux.ibm.com> writes: > The nested KVM code does not yet support HPT guests. Calling the > KVM_CAP_PPC_ALLOC_HTAB ioctl currently leads to KVM setting the guest > as HPT and erroneously executing code in L1 that should only run in > hypervisor mode, leading to an exception in the L1 vcpu thread when it > enters the nested guest. > > This can be reproduced with -machine max-cpu-compat=power8 in the L2 > guest command line. > > The KVM code has since been modified to fail the ioctl when running in > a nested environment so QEMU needs to be able to handle that. This > patch provides an error message informing the user about the lack of > support for HPT in nested guests. > I forgot to add a: Reported-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com> > Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com> > --- > hw/ppc/spapr.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 9bce1892b5..ea2c755310 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1483,6 +1483,12 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, > spapr_free_hpt(spapr); > > rc = kvmppc_reset_htab(shift); > + > + if (rc == -EOPNOTSUPP) { > + error_setg(errp, "HPT not supported in nested guests"); > + return; > + } > + > if (rc < 0) { > /* kernel-side HPT needed, but couldn't allocate one */ > error_setg_errno(errp, errno,
On Fri, Sep 11, 2020 at 01:31:23AM -0300, Fabiano Rosas wrote: > The nested KVM code does not yet support HPT guests. Calling the > KVM_CAP_PPC_ALLOC_HTAB ioctl currently leads to KVM setting the guest > as HPT and erroneously executing code in L1 that should only run in > hypervisor mode, leading to an exception in the L1 vcpu thread when it > enters the nested guest. > > This can be reproduced with -machine max-cpu-compat=power8 in the L2 > guest command line. > > The KVM code has since been modified to fail the ioctl when running in > a nested environment so QEMU needs to be able to handle that. This > patch provides an error message informing the user about the lack of > support for HPT in nested guests. > > Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com> Applied to ppc-for-5.2. > --- > hw/ppc/spapr.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 9bce1892b5..ea2c755310 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1483,6 +1483,12 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, > spapr_free_hpt(spapr); > > rc = kvmppc_reset_htab(shift); > + > + if (rc == -EOPNOTSUPP) { > + error_setg(errp, "HPT not supported in nested guests"); > + return; > + } > + > if (rc < 0) { > /* kernel-side HPT needed, but couldn't allocate one */ > error_setg_errno(errp, errno,
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 9bce1892b5..ea2c755310 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -1483,6 +1483,12 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int shift, spapr_free_hpt(spapr); rc = kvmppc_reset_htab(shift); + + if (rc == -EOPNOTSUPP) { + error_setg(errp, "HPT not supported in nested guests"); + return; + } + if (rc < 0) { /* kernel-side HPT needed, but couldn't allocate one */ error_setg_errno(errp, errno,
The nested KVM code does not yet support HPT guests. Calling the KVM_CAP_PPC_ALLOC_HTAB ioctl currently leads to KVM setting the guest as HPT and erroneously executing code in L1 that should only run in hypervisor mode, leading to an exception in the L1 vcpu thread when it enters the nested guest. This can be reproduced with -machine max-cpu-compat=power8 in the L2 guest command line. The KVM code has since been modified to fail the ioctl when running in a nested environment so QEMU needs to be able to handle that. This patch provides an error message informing the user about the lack of support for HPT in nested guests. Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com> --- hw/ppc/spapr.c | 6 ++++++ 1 file changed, 6 insertions(+)