[PATCH v2 18/37] KVM: PPC: Book3S HV P9: Use large decrementer for HDEC
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-02-25 13:54:52
Subsystem:
kernel virtual machine for powerpc (kvm/powerpc), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
On processors that don't suppress the HDEC exceptions when LPCR[HDICE]=0, this could help reduce needless guest exits due to leftover exceptions on entering the guest. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/include/asm/time.h | 2 ++ arch/powerpc/kvm/book3s_hv.c | 3 ++- 2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index 8dd3cdb25338..68d94711811e 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h@@ -18,6 +18,8 @@ #include <asm/vdso/timebase.h> /* time.c */ +extern u64 decrementer_max; + extern unsigned long tb_ticks_per_jiffy; extern unsigned long tb_ticks_per_usec; extern unsigned long tb_ticks_per_sec;
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 63cc92c45c5d..913582bd848f 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c@@ -3609,7 +3609,8 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit, vc->tb_offset_applied = 0; } - mtspr(SPRN_HDEC, 0x7fffffff); + /* HDEC must be at least as large as DEC, so decrementer_max fits */ + mtspr(SPRN_HDEC, decrementer_max); switch_mmu_to_host_radix(kvm, host_pidr);
--
2.23.0