| Message ID | 1400157833-52294-1-git-send-email-agraf@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <agraf@suse.de> [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" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 17.05.14 07:36, Paul Mackerras wrote: > 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 <agraf@suse.de> > [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. Good idea :) > >> cmpd cr0, r11, r12 >> blt slb_loop_enter >> >> + isync >> + sync > Why? Hrm, I guess I was trying to narrow down why things broke. I'll omit it and see whether my test machine can still successfully run PR KVM. > >> +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 We had that assumption before too ;) > 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. but I like warnings, so I'll add some. Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S index 596140e..aa2e2da 100644 --- a/arch/powerpc/kvm/book3s_64_slb.S +++ b/arch/powerpc/kvm/book3s_64_slb.S @@ -17,29 +17,9 @@ * Authors: Alexander Graf <agraf@suse.de> */ -#define SHADOW_SLB_ESID(num) (SLBSHADOW_SAVEAREA + (num * 0x10)) -#define SHADOW_SLB_VSID(num) (SLBSHADOW_SAVEAREA + (num * 0x10) + 0x8) -#define UNBOLT_SLB_ENTRY(num) \ - li r11, SHADOW_SLB_ESID(num); \ - LDX_BE r9, r12, r11; \ - /* Invalid? Skip. */; \ - rldicl. r0, r9, 37, 63; \ - beq slb_entry_skip_ ## num; \ - xoris r9, r9, SLB_ESID_V@h; \ - STDX_BE r9, r12, r11; \ - slb_entry_skip_ ## num: - -#define REBOLT_SLB_ENTRY(num) \ - li r8, SHADOW_SLB_ESID(num); \ - li r7, SHADOW_SLB_VSID(num); \ - LDX_BE r10, r11, r8; \ - cmpdi r10, 0; \ - beq slb_exit_skip_ ## num; \ - oris r10, r10, SLB_ESID_V@h; \ - LDX_BE r9, r11, r7; \ - slbmte r9, r10; \ - STDX_BE r10, r11, r8; \ -slb_exit_skip_ ## num: +#define SHADOW_SLB_ENTRY_LEN 0x10 +#define OFFSET_ESID(x) (SHADOW_SLB_ENTRY_LEN * x) +#define OFFSET_VSID(x) ((SHADOW_SLB_ENTRY_LEN * x) + 8) /****************************************************************************** * * @@ -63,20 +43,15 @@ slb_exit_skip_ ## num: * SVCPU[LR] = guest LR */ - /* Remove LPAR shadow entries */ +BEGIN_FW_FTR_SECTION -#if SLB_NUM_BOLTED == 3 + /* Declare SLB shadow as 0 entries big */ - ld r12, PACA_SLBSHADOWPTR(r13) + ld r11, PACA_SLBSHADOWPTR(r13) + li r8, 0 + stb r8, 3(r11) - /* Remove bolted entries */ - UNBOLT_SLB_ENTRY(0) - UNBOLT_SLB_ENTRY(1) - UNBOLT_SLB_ENTRY(2) - -#else -#error unknown number of bolted entries -#endif +END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR) /* Flush SLB */ @@ -86,6 +61,8 @@ slb_exit_skip_ ## num: /* 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 beq slb_loop_enter_skip ld r9, 8(r11) @@ -110,6 +87,9 @@ slb_loop_enter_skip: cmpd cr0, r11, r12 blt slb_loop_enter + isync + sync + slb_do_enter: .endm @@ -136,23 +116,39 @@ slb_do_enter: * */ - /* Restore bolted entries from the shadow and fix it along the way */ - - /* We don't store anything in entry 0, so we don't need to take care of it */ + /* Remove all SLB entries that are in use. */ slbia - isync -#if SLB_NUM_BOLTED == 3 + /* Restore bolted entries from the shadow */ ld r11, PACA_SLBSHADOWPTR(r13) - REBOLT_SLB_ENTRY(0) - REBOLT_SLB_ENTRY(1) - REBOLT_SLB_ENTRY(2) - -#else -#error unknown number of bolted entries -#endif +BEGIN_FW_FTR_SECTION + + /* Declare SLB shadow as SLB_NUM_BOLTED entries big */ + + li r8, SLB_NUM_BOLTED + stb r8, 3(r11) + +END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR) + + /* Manually load all entries from shadow SLB */ + + li r8, SLBSHADOW_SAVEAREA + li r7, SLBSHADOW_SAVEAREA + 8 + + .rept SLB_NUM_BOLTED + LDX_BE r10, r11, r8 + cmpdi r10, 0 + beq 1f + LDX_BE r9, r11, r7 + slbmte r9, r10 +1: addi r7, r7, SHADOW_SLB_ENTRY_LEN + addi r8, r8, SHADOW_SLB_ENTRY_LEN + .endr + + isync + sync slb_do_exit:
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. 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 <agraf@suse.de> --- arch/powerpc/kvm/book3s_64_slb.S | 90 +++++++++++++++++++--------------------- 1 file changed, 43 insertions(+), 47 deletions(-)