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[v2,18/37] KVM: PPC: Book3S HV P9: Use large decrementer for HDEC

Message ID 20210225134652.2127648-19-npiggin@gmail.com
State Superseded
Headers show
Series KVM: PPC: Book3S: C-ify the P9 entry/exit code | expand

Commit Message

Nicholas Piggin Feb. 25, 2021, 1:46 p.m. UTC 
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 mbox series

Patch

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);