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KVM: PPC: Book3S HV: Change dec_expires to be relative to guest timebase

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Change dec_expires to be relative to the guest timebase, and allow
it to be moved into low level P9 guest entry functions, to improve
SPR access scheduling.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-23-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-11-23 19:52:00 +10:00 committed by Michael Ellerman
parent cf99dedb4b
commit 3c1a4322bb
6 changed files with 49 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/powerpc/include/asm/kvm_book3s.h
View File

@ -406,6 +406,12 @@ static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu *vcpu)
return vcpu->arch.fault_dar;
}
/* Expiry time of vcpu DEC relative to host TB */
static inline u64 kvmppc_dec_expires_host_tb(struct kvm_vcpu *vcpu)
{
return vcpu->arch.dec_expires - vcpu->arch.vcore->tb_offset;
}
static inline bool is_kvmppc_resume_guest(int r)
{
return (r == RESUME_GUEST || r == RESUME_GUEST_NV);

2
arch/powerpc/include/asm/kvm_host.h
View File

@ -741,7 +741,7 @@ struct kvm_vcpu_arch {
struct hrtimer dec_timer;
u64 dec_jiffies;
u64 dec_expires;
u64 dec_expires; /* Relative to guest timebase. */
unsigned long pending_exceptions;
u8 ceded;
u8 prodded;

58
arch/powerpc/kvm/book3s_hv.c
View File

@ -2261,8 +2261,7 @@ static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
*val = get_reg_val(id, vcpu->arch.vcore->arch_compat);
break;
case KVM_REG_PPC_DEC_EXPIRY:
*val = get_reg_val(id, vcpu->arch.dec_expires +
vcpu->arch.vcore->tb_offset);
*val = get_reg_val(id, vcpu->arch.dec_expires);
break;
case KVM_REG_PPC_ONLINE:
*val = get_reg_val(id, vcpu->arch.online);
@ -2514,8 +2513,7 @@ static int kvmppc_set_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
r = kvmppc_set_arch_compat(vcpu, set_reg_val(id, *val));
break;
case KVM_REG_PPC_DEC_EXPIRY:
vcpu->arch.dec_expires = set_reg_val(id, *val) -
vcpu->arch.vcore->tb_offset;
vcpu->arch.dec_expires = set_reg_val(id, *val);
break;
case KVM_REG_PPC_ONLINE:
i = set_reg_val(id, *val);
@ -2902,13 +2900,13 @@ static void kvmppc_set_timer(struct kvm_vcpu *vcpu)
unsigned long dec_nsec, now;
now = get_tb();
if (now > vcpu->arch.dec_expires) {
if (now > kvmppc_dec_expires_host_tb(vcpu)) {
/* decrementer has already gone negative */
kvmppc_core_queue_dec(vcpu);
kvmppc_core_prepare_to_enter(vcpu);
return;
}
dec_nsec = tb_to_ns(vcpu->arch.dec_expires - now);
dec_nsec = tb_to_ns(kvmppc_dec_expires_host_tb(vcpu) - now);
hrtimer_start(&vcpu->arch.dec_timer, dec_nsec, HRTIMER_MODE_REL);
vcpu->arch.timer_running = 1;
}
@ -3380,7 +3378,7 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master)
*/
spin_unlock(&vc->lock);
/* cancel pending dec exception if dec is positive */
if (now < vcpu->arch.dec_expires &&
if (now < kvmppc_dec_expires_host_tb(vcpu) &&
kvmppc_core_pending_dec(vcpu))
kvmppc_core_dequeue_dec(vcpu);
@ -4224,20 +4222,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
load_spr_state(vcpu);
/*
* When setting DEC, we must always deal with irq_work_raise via NMI vs
* setting DEC. The problem occurs right as we switch into guest mode
* if a NMI hits and sets pending work and sets DEC, then that will
* apply to the guest and not bring us back to the host.
*
* irq_work_raise could check a flag (or possibly LPCR[HDICE] for
* example) and set HDEC to 1? That wouldn't solve the nested hv
* case which needs to abort the hcall or zero the time limit.
*
* XXX: Another day's problem.
*/
mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb);
if (kvmhv_on_pseries()) {
/*
* We need to save and restore the guest visible part of the
@ -4263,6 +4247,23 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
hvregs.vcpu_token = vcpu->vcpu_id;
}
hvregs.hdec_expiry = time_limit;
/*
* When setting DEC, we must always deal with irq_work_raise
* via NMI vs setting DEC. The problem occurs right as we
* switch into guest mode if a NMI hits and sets pending work
* and sets DEC, then that will apply to the guest and not
* bring us back to the host.
*
* irq_work_raise could check a flag (or possibly LPCR[HDICE]
* for example) and set HDEC to 1? That wouldn't solve the
* nested hv case which needs to abort the hcall or zero the
* time limit.
*
* XXX: Another day's problem.
*/
mtspr(SPRN_DEC, kvmppc_dec_expires_host_tb(vcpu) - tb);
mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
trap = plpar_hcall_norets(H_ENTER_NESTED, __pa(&hvregs),
@ -4274,6 +4275,12 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
vcpu->arch.psscr = mfspr(SPRN_PSSCR_PR);
mtspr(SPRN_PSSCR_PR, host_psscr);
dec = mfspr(SPRN_DEC);
if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
dec = (s32) dec;
tb = mftb();
vcpu->arch.dec_expires = dec + (tb + vc->tb_offset);
/* H_CEDE has to be handled now, not later */
if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
kvmppc_get_gpr(vcpu, 3) == H_CEDE) {
@ -4281,6 +4288,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
kvmppc_set_gpr(vcpu, 3, 0);
trap = 0;
}
} else {
kvmppc_xive_push_vcpu(vcpu);
trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr);
@ -4312,12 +4320,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
vcpu->arch.slb_max = 0;
}
dec = mfspr(SPRN_DEC);
if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
dec = (s32) dec;
tb = mftb();
vcpu->arch.dec_expires = dec + tb;
store_spr_state(vcpu);
restore_p9_host_os_sprs(vcpu, &host_os_sprs);
@ -4827,7 +4829,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
* by L2 and the L1 decrementer is provided in hdec_expires
*/
if (kvmppc_core_pending_dec(vcpu) &&
((get_tb() < vcpu->arch.dec_expires) ||
((get_tb() < kvmppc_dec_expires_host_tb(vcpu)) ||
(trap == BOOK3S_INTERRUPT_SYSCALL &&
kvmppc_get_gpr(vcpu, 3) == H_ENTER_NESTED)))
kvmppc_core_dequeue_dec(vcpu);

3
arch/powerpc/kvm/book3s_hv_nested.c
View File

@ -358,6 +358,7 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
/* convert TB values/offsets to host (L0) values */
hdec_exp = l2_hv.hdec_expiry - vc->tb_offset;
vc->tb_offset += l2_hv.tb_offset;
vcpu->arch.dec_expires += l2_hv.tb_offset;
/* set L1 state to L2 state */
vcpu->arch.nested = l2;
@ -399,6 +400,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
if (l2_regs.msr & MSR_TS_MASK)
vcpu->arch.shregs.msr |= MSR_TS_S;
vc->tb_offset = saved_l1_hv.tb_offset;
/* XXX: is this always the same delta as saved_l1_hv.tb_offset? */
vcpu->arch.dec_expires -= l2_hv.tb_offset;
restore_hv_regs(vcpu, &saved_l1_hv);
vcpu->arch.purr += delta_purr;
vcpu->arch.spurr += delta_spurr;

10
arch/powerpc/kvm/book3s_hv_p9_entry.c
View File

@ -188,7 +188,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
struct kvm *kvm = vcpu->kvm;
struct kvm_nested_guest *nested = vcpu->arch.nested;
struct kvmppc_vcore *vc = vcpu->arch.vcore;
s64 hdec;
s64 hdec, dec;
u64 tb, purr, spurr;
u64 *exsave;
bool ri_set;
@ -317,6 +317,8 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
*/
mtspr(SPRN_HDEC, hdec);
mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb);
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
tm_return_to_guest:
#endif
@ -461,6 +463,12 @@ tm_return_to_guest:
vcpu->arch.shregs.sprg2 = mfspr(SPRN_SPRG2);
vcpu->arch.shregs.sprg3 = mfspr(SPRN_SPRG3);
dec = mfspr(SPRN_DEC);
if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
dec = (s32) dec;
tb = mftb();
vcpu->arch.dec_expires = dec + tb;
/* Preserve PSSCR[FAKE_SUSPEND] until we've called kvmppc_save_tm_hv */
mtspr(SPRN_PSSCR, host_psscr |
(local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));

13
arch/powerpc/kvm/book3s_hv_rmhandlers.S
View File

@ -814,10 +814,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
* Set the decrementer to the guest decrementer.
*/
ld r8,VCPU_DEC_EXPIRES(r4)
/* r8 is a host timebase value here, convert to guest TB */
ld r5,HSTATE_KVM_VCORE(r13)
ld r6,VCORE_TB_OFFSET_APPL(r5)
add r8,r8,r6
mftb r7
subf r3,r7,r8
mtspr SPRN_DEC,r3
@ -1192,9 +1188,6 @@ guest_bypass:
mftb r6
extsw r5,r5
16: add r5,r5,r6
/* r5 is a guest timebase value here, convert to host TB */
ld r4,VCORE_TB_OFFSET_APPL(r3)
subf r5,r4,r5
std r5,VCPU_DEC_EXPIRES(r9)
/* Increment exit count, poke other threads to exit */
@ -2160,9 +2153,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_TM)
/* save expiry time of guest decrementer */
add r3, r3, r5
ld r4, HSTATE_KVM_VCPU(r13)
ld r5, HSTATE_KVM_VCORE(r13)
ld r6, VCORE_TB_OFFSET_APPL(r5)
subf r3, r6, r3 /* convert to host TB value */
std r3, VCPU_DEC_EXPIRES(r4)
#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
@ -2259,9 +2249,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_TM)
/* Restore guest decrementer */
ld r3, VCPU_DEC_EXPIRES(r4)
ld r5, HSTATE_KVM_VCORE(r13)
ld r6, VCORE_TB_OFFSET_APPL(r5)
add r3, r3, r6 /* convert host TB to guest TB value */
mftb r7
subf r3, r7, r3
mtspr SPRN_DEC, r3