Commit 2f272463 authored by Paul Mackerras's avatar Paul Mackerras

KVM: PPC: Book3S HV: Cope with host using large decrementer mode

POWER9 introduces a new mode for the decrementer register, called
large decrementer mode, in which the decrementer counter is 56 bits
wide rather than 32, and reads are sign-extended rather than
zero-extended.  For the decrementer, this new mode is optional and
controlled by a bit in the LPCR.  The hypervisor decrementer (HDEC)
is 56 bits wide on POWER9 and has no mode control.

Since KVM code reads and writes the decrementer and hypervisor
decrementer registers in a few places, it needs to be aware of the
need to treat the decrementer value as a 64-bit quantity, and only do
a 32-bit sign extension when large decrementer mode is not in effect.
Similarly, the HDEC should always be treated as a 64-bit quantity on
POWER9.  We define a new EXTEND_HDEC macro to encapsulate the feature
test for POWER9 and the sign extension.

To enable the sign extension to be removed in large decrementer mode,
we test the LPCR_LD bit in the host LPCR image stored in the struct
kvm for the guest.  If is set then large decrementer mode is enabled
and the sign extension should be skipped.

This is partly based on an earlier patch by Oliver O'Halloran.

Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent 08332893
......@@ -121,10 +121,20 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
* Put whatever is in the decrementer into the
* hypervisor decrementer.
*/
BEGIN_FTR_SECTION
ld r5, HSTATE_KVM_VCORE(r13)
ld r6, VCORE_KVM(r5)
ld r9, KVM_HOST_LPCR(r6)
andis. r9, r9, LPCR_LD@h
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
mfspr r8,SPRN_DEC
mftb r7
mtspr SPRN_HDEC,r8
BEGIN_FTR_SECTION
/* On POWER9, don't sign-extend if host LPCR[LD] bit is set */
bne 32f
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
extsw r8,r8
32: mtspr SPRN_HDEC,r8
add r8,r8,r7
std r8,HSTATE_DECEXP(r13)
......
......@@ -32,6 +32,12 @@
#include <asm/opal.h>
#include <asm/xive-regs.h>
/* Sign-extend HDEC if not on POWER9 */
#define EXTEND_HDEC(reg) \
BEGIN_FTR_SECTION; \
extsw reg, reg; \
END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
#define VCPU_GPRS_TM(reg) (((reg) * ULONG_SIZE) + VCPU_GPR_TM)
/* Values in HSTATE_NAPPING(r13) */
......@@ -214,6 +220,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
kvmppc_primary_no_guest:
/* We handle this much like a ceded vcpu */
/* put the HDEC into the DEC, since HDEC interrupts don't wake us */
/* HDEC may be larger than DEC for arch >= v3.00, but since the */
/* HDEC value came from DEC in the first place, it will fit */
mfspr r3, SPRN_HDEC
mtspr SPRN_DEC, r3
/*
......@@ -295,8 +303,9 @@ kvm_novcpu_wakeup:
/* See if our timeslice has expired (HDEC is negative) */
mfspr r0, SPRN_HDEC
EXTEND_HDEC(r0)
li r12, BOOK3S_INTERRUPT_HV_DECREMENTER
cmpwi r0, 0
cmpdi r0, 0
blt kvm_novcpu_exit
/* Got an IPI but other vcpus aren't yet exiting, must be a latecomer */
......@@ -390,8 +399,8 @@ kvm_secondary_got_guest:
lbz r4, HSTATE_PTID(r13)
cmpwi r4, 0
bne 63f
lis r6, 0x7fff
ori r6, r6, 0xffff
LOAD_REG_ADDR(r6, decrementer_max)
ld r6, 0(r6)
mtspr SPRN_HDEC, r6
/* and set per-LPAR registers, if doing dynamic micro-threading */
ld r6, HSTATE_SPLIT_MODE(r13)
......@@ -968,7 +977,8 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
/* Check if HDEC expires soon */
mfspr r3, SPRN_HDEC
cmpwi r3, 512 /* 1 microsecond */
EXTEND_HDEC(r3)
cmpdi r3, 512 /* 1 microsecond */
blt hdec_soon
#ifdef CONFIG_KVM_XICS
......@@ -2366,12 +2376,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM)
mfspr r3, SPRN_DEC
mfspr r4, SPRN_HDEC
mftb r5
cmpw r3, r4
extsw r3, r3
EXTEND_HDEC(r4)
cmpd r3, r4
ble 67f
mtspr SPRN_DEC, r4
67:
/* save expiry time of guest decrementer */
extsw r3, r3
add r3, r3, r5
ld r4, HSTATE_KVM_VCPU(r13)
ld r5, HSTATE_KVM_VCORE(r13)
......
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