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@xxxxxxx>
[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@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
