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Donenfeld" To: Fabiano Rosas , linuxppc-dev@lists.ozlabs.org, LKML , Michael Ellerman Subject: [PATCH v2 2/2] powerpc/kvm: don't crash on missing rng, and use darn Date: Fri, 24 Jun 2022 16:23:22 +0200 Message-Id: <20220624142322.2049826-3-Jason@zx2c4.com> In-Reply-To: <20220624142322.2049826-1-Jason@zx2c4.com> References: <20220624142322.2049826-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Jason A. Donenfeld" , stable@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 implementation.") Signed-off-by: Jason A. Donenfeld --- arch/powerpc/include/asm/archrandom.h | 5 ---- arch/powerpc/kvm/book3s_hv_builtin.c | 7 +++--- arch/powerpc/platforms/powernv/rng.c | 33 +++++++-------------------- 3 files changed, 12 insertions(+), 33 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..3abaef5f9ac2 100644 --- a/arch/powerpc/kvm/book3s_hv_builtin.c +++ b/arch/powerpc/kvm/book3s_hv_builtin.c @@ -19,7 +19,7 @@ #include #include #include -#include +#include #include #include #include @@ -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; 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; } -- 2.35.1