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KVM: PPC: Book3S HV: Lockless tlbie for HPT hcalls

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tlbies to an LPAR do not have to be serialised since POWER4/PPC970,
after which the MMU_FTR_LOCKLESS_TLBIE feature was introduced to
avoid tlbie locking.

Since commit c17b98cf60 ("KVM: PPC: Book3S HV: Remove code for
PPC970 processors"), KVM no longer supports processors that do not
have this feature, so the tlbie locking can be removed completely.
A sanity check for the feature is put in kvmppc_mmu_hv_init.

Testing was done on a POWER9 system in HPT mode, with a -smp 32 guest
in HPT mode. 32 instances of the powerpc fork benchmark from selftests
were run with --fork, and the results measured.

Without this patch, total throughput was about 13.5K/sec, and this is
the top of the host profile:

   74.52%  [k] do_tlbies
    2.95%  [k] kvmppc_book3s_hv_page_fault
    1.80%  [k] calc_checksum
    1.80%  [k] kvmppc_vcpu_run_hv
    1.49%  [k] kvmppc_run_core

After this patch, throughput was about 51K/sec, with this profile:

   21.28%  [k] do_tlbies
    5.26%  [k] kvmppc_run_core
    4.88%  [k] kvmppc_book3s_hv_page_fault
    3.30%  [k] _raw_spin_lock_irqsave
    3.25%  [k] gup_pgd_range

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Nicholas Piggin 2018-05-17 16:59:10 +10:00 committed by Paul Mackerras
parent f19d1f367a
commit b755745147
3 changed files with 3 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/kvm_host.h
View File

@ -269,7 +269,6 @@ struct kvm_arch {
unsigned long host_lpcr;
unsigned long sdr1;
unsigned long host_sdr1;
int tlbie_lock;
unsigned long lpcr;
unsigned long vrma_slb_v;
int mmu_ready;

3
arch/powerpc/kvm/book3s_64_mmu_hv.c
View File

@ -272,6 +272,9 @@ int kvmppc_mmu_hv_init(void)
if (!cpu_has_feature(CPU_FTR_HVMODE))
return -EINVAL;
if (!mmu_has_feature(MMU_FTR_LOCKLESS_TLBIE))
return -EINVAL;
/* POWER7 has 10-bit LPIDs (12-bit in POWER8) */
host_lpid = mfspr(SPRN_LPID);
rsvd_lpid = LPID_RSVD;

21
arch/powerpc/kvm/book3s_hv_rm_mmu.c
View File

@ -435,24 +435,6 @@ static inline int is_mmio_hpte(unsigned long v, unsigned long r)
(HPTE_R_KEY_HI | HPTE_R_KEY_LO));
}
static inline int try_lock_tlbie(unsigned int *lock)
{
unsigned int tmp, old;
unsigned int token = LOCK_TOKEN;
asm volatile("1:lwarx %1,0,%2\n"
" cmpwi cr0,%1,0\n"
" bne 2f\n"
" stwcx. %3,0,%2\n"
" bne- 1b\n"
" isync\n"
"2:"
: "=&r" (tmp), "=&r" (old)
: "r" (lock), "r" (token)
: "cc", "memory");
return old == 0;
}
static void do_tlbies(struct kvm *kvm, unsigned long *rbvalues,
long npages, int global, bool need_sync)
{
@ -464,8 +446,6 @@ static void do_tlbies(struct kvm *kvm, unsigned long *rbvalues,
* the RS field, this is backwards-compatible with P7 and P8.
*/
if (global) {
while (!try_lock_tlbie(&kvm->arch.tlbie_lock))
cpu_relax();
if (need_sync)
asm volatile("ptesync" : : : "memory");
for (i = 0; i < npages; ++i) {
@ -484,7 +464,6 @@ static void do_tlbies(struct kvm *kvm, unsigned long *rbvalues,
}
asm volatile("eieio; tlbsync; ptesync" : : : "memory");
kvm->arch.tlbie_lock = 0;
} else {
if (need_sync)
asm volatile("ptesync" : : : "memory");