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Donenfeld" To: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Cc: "Jason A. Donenfeld" , stable@vger.kernel.org, Michael Ellerman Subject: [PATCH] powerpc/kvm: don't crash on missing rng, and use darn Date: Wed, 22 Jun 2022 12:54:35 +0200 Message-Id: <20220622105435.203922-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 Fixes: e928e9cb3601 ("KVM: PPC: Book3S HV: Add fast real-mode H_RANDOM impl= ementation.") Signed-off-by: Jason A. Donenfeld --- This patch must be applied ontop of: 1) https://github.com/linuxppc/linux/commit/f3eac426657d985b97c92fa5f7ae1d4= 3f04721f3 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/a= sm/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 */ =20 #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 =20 #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); =20 int kvmppc_hwrng_present(void) { - return pnv_hwrng_present(); + return ppc_md.get_random_seed !=3D NULL; } EXPORT_SYMBOL_GPL(kvmppc_hwrng_present); =20 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; =20 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 { =20 static DEFINE_PER_CPU(struct pnv_rng *, pnv_rng); =20 -int pnv_hwrng_present(void) -{ - struct pnv_rng *rng; - - rng =3D get_cpu_var(pnv_rng); - put_cpu_var(rng); - return rng !=3D 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, uns= igned long val) return val; } =20 -int pnv_get_random_real_mode(unsigned long *v) -{ - struct pnv_rng *rng; - - rng =3D raw_cpu_read(pnv_rng); - - *v =3D 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; =20 - rng =3D get_cpu_var(pnv_rng); - - *v =3D rng_whiten(rng, in_be64(rng->regs)); - - put_cpu_var(rng); + if (mfmsr() & MSR_DR) { + rng =3D raw_cpu_read(pnv_rng); + *v =3D rng_whiten(rng, __raw_rm_readq(rng->regs_real)); + } else { + rng =3D get_cpu_var(pnv_rng); + *v =3D rng_whiten(rng, in_be64(rng->regs)); + put_cpu_var(rng); + } =20 return 1; } --=20 2.35.1