From: Nicholas Piggin Date: Wed, 22 Nov 2023 02:58:11 +0000 (+1000) Subject: KVM: PPC: Book3S HV: Fix KVM_RUN clobbering FP/VEC user registers X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=dc158d23b33df9033bcc8e7117e8591dd2f9d125;p=linux.git KVM: PPC: Book3S HV: Fix KVM_RUN clobbering FP/VEC user registers Before running a guest, the host process (e.g., QEMU) FP/VEC registers are saved if they were being used, similarly to when the kernel uses FP registers. The guest values are then loaded into regs, and the host process registers will be restored lazily when it uses FP/VEC. KVM HV has a bug here: the host process registers do get saved, but the user MSR bits remain enabled, which indicates the registers are valid for the process. After they are clobbered by running the guest, this valid indication causes the host process to take on the FP/VEC register values of the guest. Fixes: 34e119c96b2b ("KVM: PPC: Book3S HV P9: Reduce mtmsrd instructions required to save host SPRs") Cc: stable@vger.kernel.org # v5.17+ Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://msgid.link/20231122025811.2973-1-npiggin@gmail.com --- diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 392404688cec3..9452a54d356c9 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1198,11 +1198,11 @@ void kvmppc_save_user_regs(void) usermsr = current->thread.regs->msr; + /* Caller has enabled FP/VEC/VSX/TM in MSR */ if (usermsr & MSR_FP) - save_fpu(current); - + __giveup_fpu(current); if (usermsr & MSR_VEC) - save_altivec(current); + __giveup_altivec(current); #ifdef CONFIG_PPC_TRANSACTIONAL_MEM if (usermsr & MSR_TM) {