[+ Christoffer] On 10/10/17 19:38, Dave Martin wrote: > KVM guests cannot currently use SVE, because SVE is always > configured to trap to EL2. > > However, a guest that sees SVE reported as present in > ID_AA64PFR0_EL1 may legitimately expect that SVE works and try to > use it. Instead of working, the guest will receive an injected > undef exception, which may cause the guest to oops or go into a > spin. > > To avoid misleading the guest into believing that SVE will work, > this patch masks out the SVE field from ID_AA64PFR0_EL1 when a > guest attempts to read this register. No support is explicitly > added for ID_AA64ZFR0_EL1 either, so that is still emulated as > reading as zero, which is consistent with SVE not being > implemented. > > This is a temporary measure, and will be removed in a later series > when full KVM support for SVE is implemented. > > Signed-off-by: Dave Martin <[email protected]> > Reviewed-by: Alex Bennée <[email protected]> > Cc: Marc Zyngier <[email protected]> > --- > arch/arm64/kvm/sys_regs.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index b1f7552..a0ee9b0 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -23,6 +23,7 @@ > #include <linux/bsearch.h> > #include <linux/kvm_host.h> > #include <linux/mm.h> > +#include <linux/printk.h> > #include <linux/uaccess.h> > > #include <asm/cacheflush.h> > @@ -897,8 +898,17 @@ static u64 read_id_reg(struct sys_reg_desc const *r, > bool raz) > { > u32 id = sys_reg((u32)r->Op0, (u32)r->Op1, > (u32)r->CRn, (u32)r->CRm, (u32)r->Op2); > + u64 val = raz ? 0 : read_sanitised_ftr_reg(id); > > - return raz ? 0 : read_sanitised_ftr_reg(id); > + if (id == SYS_ID_AA64PFR0_EL1) { > + if (val & (0xfUL << ID_AA64PFR0_SVE_SHIFT)) > + pr_err_once("kvm [%i]: SVE unsupported for guests, > suppressing\n", > + task_pid_nr(current)); > + > + val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT); > + } > + > + return val; > } > > /* cpufeature ID register access trap handlers */ >
Acked-by: Marc Zyngier <[email protected]> M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
