On entering a PR KVM guest, we invalidate the whole SLB before loading up the guest entries. We do this using an slbia instruction, which invalidates all entries except entry 0, followed by an slbie to invalidate entry 0. However, the slbie turns out to be ineffective in some circumstances (specifically when the host linear mapping uses 64k pages) because of errors in computing the parameter to the slbie. The result is that the guest kernel hangs very early in boot because it takes a DSI the first time it tries to access kernel data using a linear mapping address in real mode. Currently we construct bits 36 - 43 (big-endian numbering) of the slbie parameter by taking bits 56 - 63 of the SLB VSID doubleword. These bits for the tlbie are C (class, 1 bit), B (segment size, 2 bits) and 5 reserved bits. For the SLB VSID doubleword these are C (class, 1 bit), reserved (1 bit), LP (large page size, 2 bits), and 4 reserved bits. Thus we are not setting the B field correctly, and when LP = 01 as it is for 64k pages, we are setting a reserved bit. Rather than add more instructions to calculate the slbie parameter correctly, this takes a simpler approach, which is to set entry 0 to zeroes explicitly. Normally slbmte should not be used to invalidate an entry, since it doesn't invalidate the ERATs, but it is OK to use it to invalidate an entry if it is immediately followed by slbia, which does invalidate the ERATs. (This has been confirmed with the Power architects.) This approach takes fewer instructions and will work whatever the contents of entry 0. Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx> --- arch/powerpc/kvm/book3s_64_slb.S | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S index 56b983e..4f0caec 100644 --- a/arch/powerpc/kvm/book3s_64_slb.S +++ b/arch/powerpc/kvm/book3s_64_slb.S @@ -66,10 +66,6 @@ slb_exit_skip_ ## num: ld r12, PACA_SLBSHADOWPTR(r13) - /* Save off the first entry so we can slbie it later */ - ld r10, SHADOW_SLB_ESID(0)(r12) - ld r11, SHADOW_SLB_VSID(0)(r12) - /* Remove bolted entries */ UNBOLT_SLB_ENTRY(0) UNBOLT_SLB_ENTRY(1) @@ -81,15 +77,10 @@ slb_exit_skip_ ## num: /* Flush SLB */ + li r10, 0 + slbmte r10, r10 slbia - /* r0 = esid & ESID_MASK */ - rldicr r10, r10, 0, 35 - /* r0 |= CLASS_BIT(VSID) */ - rldic r12, r11, 56 - 36, 36 - or r10, r10, r12 - slbie r10 - /* Fill SLB with our shadow */ lbz r12, SVCPU_SLB_MAX(r3) -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
