Re: [PATCH v4 44/46] KVM: PPC: Book3S HV P9: implement hash guest support

Excerpts from Fabiano Rosas's message of March 24, 2021 1:53 am:

Nicholas Piggin [off-list ref] writes:

quoted

Guest entry/exit has to restore and save/clear the SLB, plus several
other bits to accommodate hash guests in the P9 path.

Radix host, hash guest support is removed from the P7/8 path.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---

<snip>

quoted

diff --git a/arch/powerpc/kvm/book3s_hv_interrupt.c b/arch/powerpc/kvm/book3s_hv_interrupt.c
index cd84d2c37632..03fbfef708a8 100644
--- a/arch/powerpc/kvm/book3s_hv_interrupt.c
+++ b/arch/powerpc/kvm/book3s_hv_interrupt.c

@@ -55,6 +55,50 @@ static void __accumulate_time(struct kvm_vcpu *vcpu, struct kvmhv_tb_accumulator
 #define accumulate_time(vcpu, next) do {} while (0)
 #endif

+static inline void mfslb(unsigned int idx, u64 *slbee, u64 *slbev)
+{
+	asm volatile("slbmfev  %0,%1" : "=r" (*slbev) : "r" (idx));
+	asm volatile("slbmfee  %0,%1" : "=r" (*slbee) : "r" (idx));
+}
+
+static inline void __mtslb(u64 slbee, u64 slbev)
+{
+	asm volatile("slbmte %0,%1" :: "r" (slbev), "r" (slbee));
+}
+
+static inline void mtslb(unsigned int idx, u64 slbee, u64 slbev)
+{
+	BUG_ON((slbee & 0xfff) != idx);
+
+	__mtslb(slbee, slbev);
+}
+
+static inline void slb_invalidate(unsigned int ih)
+{
+	asm volatile("slbia %0" :: "i"(ih));
+}

Fyi, in my environment the assembler complains:

{standard input}: Assembler messages:                                    
{standard input}:1293: Error: junk at end of line: `6'                             
{standard input}:2138: Error: junk at end of line: `6'                    
make[3]: *** [../scripts/Makefile.build:271:
arch/powerpc/kvm/book3s_hv_interrupt.o] Error 1

This works:

-       asm volatile("slbia %0" :: "i"(ih));
+       asm volatile(PPC_SLBIA(%0) :: "i"(ih));

But I don't know what is going on.

Ah yes, we still need to use PPC_SLBIA. IH parameter to slbia was only 
added in binutils 2.27 and we support down to 2.23.

Thanks for the fix I'll add it.

Thanks,
Nick