"Jason A. Donenfeld" Jason@zx2c4.com 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@vger.kernel.org # v4.1+ Cc: Michael Ellerman mpe@ellerman.id.au Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM implementation.") Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com

---

This patch must be applied ontop of:

1. https://github.com/linuxppc/linux/commit/f3eac426657d985b97c92fa5f7ae1d43f04...
2. https://lore.kernel.org/all/20220622102532.173393-1-Jason@zx2c4.com/

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;

}