From: Suresh E. Warrier Date: Mon, 3 Nov 2014 04:46:42 +0000 (+1100) Subject: powerpc: Save/restore PPR for KVM hypercalls X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8b91a2554610ac5e341de8fb0b5715fe90a0f2e2;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git powerpc: Save/restore PPR for KVM hypercalls The system call FLIH (first-level interrupt handler) at 0xc00 unconditionally sets hardware priority to medium. For hypercalls, this means we lose guest OS priority. The front end (do_kvm_0x**) to the KVM interrupt handler always assumes that PPR priority is saved in PACA exception save area, so it copies this to the kvm_hstate structure. For hypercalls, this would be the saved priority from any previous exception. Eventually, the guest gets resumed with an incorrect priority. The fix is to save the PPR priority in PACA exception save area before switching HMT priorities in the FLIH so that existing code described above in the KVM interrupt handler can copy it from there into the VCPU's saved context. Signed-off-by: Suresh Warrier Signed-off-by: Paul Mackerras [mpe: Dropped HMT_MEDIUM_PPR_DISCARD and reworded comment] Signed-off-by: Michael Ellerman --- diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 72e783ea0681..a1d45c161e24 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -292,15 +292,26 @@ decrementer_pSeries: . = 0xc00 .globl system_call_pSeries system_call_pSeries: - HMT_MEDIUM + /* + * If CONFIG_KVM_BOOK3S_64_HANDLER is set, save the PPR (on systems + * that support it) before changing to HMT_MEDIUM. That allows the KVM + * code to save that value into the guest state (it is the guest's PPR + * value). Otherwise just change to HMT_MEDIUM as userspace has + * already saved the PPR. + */ #ifdef CONFIG_KVM_BOOK3S_64_HANDLER SET_SCRATCH0(r13) GET_PACA(r13) std r9,PACA_EXGEN+EX_R9(r13) + OPT_GET_SPR(r9, SPRN_PPR, CPU_FTR_HAS_PPR); + HMT_MEDIUM; std r10,PACA_EXGEN+EX_R10(r13) + OPT_SAVE_REG_TO_PACA(PACA_EXGEN+EX_PPR, r9, CPU_FTR_HAS_PPR); mfcr r9 KVMTEST(0xc00) GET_SCRATCH0(r13) +#else + HMT_MEDIUM; #endif SYSCALL_PSERIES_1 SYSCALL_PSERIES_2_RFID