"Jason A. Donenfeld" <Jason@xxxxxxxxx> writes: > On POWER8 systems that don't have ibm,power-rng available, a guest that > ignores the KVM_CAP_PPC_HWRNG flag and calls H_RANDOM anyway will > dereference a NULL pointer. And on machines with darn instead of > ibm,power-rng, H_RANDOM won't work at all. > > This patch kills two birds with one stone, by routing H_RANDOM calls to > ppc_md.get_random_seed, and doing the real mode check inside of it. > > Cc: stable@xxxxxxxxxxxxxxx # v4.1+ > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.") > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> > --- > > This patch must be applied ontop of: > 1) https://github.com/linuxppc/linux/commit/f3eac426657d985b97c92fa5f7ae1d43f04721f3 > 2) https://lore.kernel.org/all/20220622102532.173393-1-Jason@xxxxxxxxx/ > > > arch/powerpc/include/asm/archrandom.h | 5 ---- > arch/powerpc/kvm/book3s_hv_builtin.c | 5 ++-- > arch/powerpc/platforms/powernv/rng.c | 33 +++++++-------------------- > 3 files changed, 11 insertions(+), 32 deletions(-) > > diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h > index 11d4815841ab..3af27bb84a3d 100644 > --- a/arch/powerpc/include/asm/archrandom.h > +++ b/arch/powerpc/include/asm/archrandom.h > @@ -38,12 +38,7 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v) > #endif /* CONFIG_ARCH_RANDOM */ > > #ifdef CONFIG_PPC_POWERNV > -int pnv_hwrng_present(void); > int pnv_get_random_long(unsigned long *v); > -int pnv_get_random_real_mode(unsigned long *v); > -#else > -static inline int pnv_hwrng_present(void) { return 0; } > -static inline int pnv_get_random_real_mode(unsigned long *v) { return 0; } > #endif > > #endif /* _ASM_POWERPC_ARCHRANDOM_H */ > diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c > index 799d40c2ab4f..1c6672826db5 100644 > --- a/arch/powerpc/kvm/book3s_hv_builtin.c > +++ b/arch/powerpc/kvm/book3s_hv_builtin.c > @@ -176,13 +176,14 @@ EXPORT_SYMBOL_GPL(kvmppc_hcall_impl_hv_realmode); > > int kvmppc_hwrng_present(void) > { > - return pnv_hwrng_present(); > + return ppc_md.get_random_seed != NULL; > } > EXPORT_SYMBOL_GPL(kvmppc_hwrng_present); > > long kvmppc_rm_h_random(struct kvm_vcpu *vcpu) > { > - if (pnv_get_random_real_mode(&vcpu->arch.regs.gpr[4])) > + if (ppc_md.get_random_seed && > + ppc_md.get_random_seed(&vcpu->arch.regs.gpr[4])) > return H_SUCCESS; This is the same as arch_get_random_seed_long, perhaps you could use it instead. Otherwise, the archrandom.h include is not needed anymore and could be replaced with #include <asm/machdep.h> for ppc_md. > > return H_HARDWARE; > diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c > index 868bb9777425..c748567cd47e 100644 > --- a/arch/powerpc/platforms/powernv/rng.c > +++ b/arch/powerpc/platforms/powernv/rng.c > @@ -29,15 +29,6 @@ struct pnv_rng { > > static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng); > > -int pnv_hwrng_present(void) > -{ > - struct pnv_rng *rng; > - > - rng = get_cpu_var(pnv_rng); > - put_cpu_var(rng); > - return rng != NULL; > -} > - > static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) > { > unsigned long parity; > @@ -58,17 +49,6 @@ static unsigned long rng_whiten(struct pnv_rng *rng, unsigned long val) > return val; > } > > -int pnv_get_random_real_mode(unsigned long *v) > -{ > - struct pnv_rng *rng; > - > - rng = raw_cpu_read(pnv_rng); > - > - *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); > - > - return 1; > -} > - > static int pnv_get_random_darn(unsigned long *v) > { > unsigned long val; > @@ -105,11 +85,14 @@ int pnv_get_random_long(unsigned long *v) > { > struct pnv_rng *rng; > > - rng = get_cpu_var(pnv_rng); > - > - *v = rng_whiten(rng, in_be64(rng->regs)); > - > - put_cpu_var(rng); > + if (mfmsr() & MSR_DR) { > + rng = raw_cpu_read(pnv_rng); > + *v = rng_whiten(rng, __raw_rm_readq(rng->regs_real)); > + } else { > + rng = get_cpu_var(pnv_rng); > + *v = rng_whiten(rng, in_be64(rng->regs)); > + put_cpu_var(rng); > + } > > return 1; > }