On Thu, May 15, 2014 at 02:43:53PM +0200, Alexander Graf wrote: > On LPAR guest systems Linux enables the shadow SLB to indicate to the > hypervisor a number of SLB entries that always have to be available. > > Today we go through this shadow SLB and disable all ESID's valid bits. > However, pHyp doesn't like this approach very much and honors us with > fancy machine checks. > > Fortunately the shadow SLB descriptor also has an entry that indicates > the number of valid entries following. During the lifetime of a guest > we can just swap that value to 0 and don't have to worry about the > SLB restoration magic.
I think this is a great idea; I have been thinking we should do something like this. > While we're touching the code, let's also make it more readable (get > rid of rldicl), allow it to deal with a dynamic number of bolted > SLB entries and only do shadow SLB swizzling on LPAR systems. > > Signed-off-by: Alexander Graf <[email protected]> [snip] > +#define SHADOW_SLB_ENTRY_LEN 0x10 Normally we'd define structure offsets/sizes like this in asm-offsets.c. However, since the structure can't change I guess this is OK. > /* Fill SLB with our shadow */ > > + lis r7, SLB_ESID_V@h > + > lbz r12, SVCPU_SLB_MAX(r3) > mulli r12, r12, 16 > addi r12, r12, SVCPU_SLB > @@ -99,7 +76,7 @@ slb_loop_enter: > > ld r10, 0(r11) > > - rldicl. r0, r10, 37, 63 > + and. r9, r10, r7 Or... andis. r9, r10, SLB_ESID_V@h and save a register and an instruction. > cmpd cr0, r11, r12 > blt slb_loop_enter > > + isync > + sync Why? > +BEGIN_FW_FTR_SECTION > + > + /* Declare SLB shadow as SLB_NUM_BOLTED entries big */ > + > + li r8, SLB_NUM_BOLTED > + stb r8, 3(r11) Currently it's true that slb_shadow.persistent is always SLB_NUM_BOLTED, but if you are going to embed that assumption here in the KVM code you should at least add some comments over in arch/powerpc/mm/slb.c and in arch/powerpc/kernel/paca.c (where slb_shadow.persistent gets initialized) warning people that if they break that assumption they need to fix KVM code as well. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
