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authorDavid Gibson <david@gibson.dropbear.id.au>2012-09-20 17:42:30 +0000
committerAlexander Graf <agraf@suse.de>2012-10-04 15:54:18 +0200
commit35f9304d925a5423c51bd2c83a81fa3cc2b6e680 (patch)
tree47c972d944fc2b043b27f300e776d53fa0709be4
parent5a1972c8472fafd519a68b689fdcaf33ec857945 (diff)
pseries: Remove unnecessary locking from PAPR hash table hcalls
In the paravirtualized environment provided by PAPR, there is a standard locking scheme so that hypercalls updating the hash page table from different guest threads don't corrupt the haah table state. We implement this HVLOCK bit in out page table hypercalls. However, it is not necessary in our case, since the hypercalls all run in the qemu environment under the big qemu lock. Therefore, this patch removes the locking code. This has the additional advantage of freeing up a hash PTE bit which will be useful for migration support. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Alexander Graf <agraf@suse.de>
-rw-r--r--hw/spapr_hcall.c42
1 files changed, 4 insertions, 38 deletions
diff --git a/hw/spapr_hcall.c b/hw/spapr_hcall.c
index 2df94d197a..826ca673fc 100644
--- a/hw/spapr_hcall.c
+++ b/hw/spapr_hcall.c
@@ -39,22 +39,6 @@
#define HPTE_V_1TB_SEG 0x4000000000000000ULL
#define HPTE_V_VRMA_MASK 0x4001ffffff000000ULL
-#define HPTE_V_HVLOCK 0x40ULL
-
-static inline int lock_hpte(void *hpte, target_ulong bits)
-{
- uint64_t pteh;
-
- pteh = ldq_p(hpte);
-
- /* We're protected by qemu's global lock here */
- if (pteh & bits) {
- return 0;
- }
- stq_p(hpte, pteh | HPTE_V_HVLOCK);
- return 1;
-}
-
static target_ulong compute_tlbie_rb(target_ulong v, target_ulong r,
target_ulong pte_index)
{
@@ -151,8 +135,7 @@ static target_ulong h_enter(CPUPPCState *env, sPAPREnvironment *spapr,
if (i == 8) {
return H_PTEG_FULL;
}
- if (((ldq_p(hpte) & HPTE_V_VALID) == 0) &&
- lock_hpte(hpte, HPTE_V_HVLOCK | HPTE_V_VALID)) {
+ if ((ldq_p(hpte) & HPTE_V_VALID) == 0) {
break;
}
hpte += HASH_PTE_SIZE_64;
@@ -160,7 +143,7 @@ static target_ulong h_enter(CPUPPCState *env, sPAPREnvironment *spapr,
} else {
i = 0;
hpte = env->external_htab + (pte_index * HASH_PTE_SIZE_64);
- if (!lock_hpte(hpte, HPTE_V_HVLOCK | HPTE_V_VALID)) {
+ if (ldq_p(hpte) & HPTE_V_VALID) {
return H_PTEG_FULL;
}
}
@@ -168,7 +151,6 @@ static target_ulong h_enter(CPUPPCState *env, sPAPREnvironment *spapr,
/* eieio(); FIXME: need some sort of barrier for smp? */
stq_p(hpte, pteh);
- assert(!(ldq_p(hpte) & HPTE_V_HVLOCK));
args[0] = pte_index + i;
return H_SUCCESS;
}
@@ -193,11 +175,6 @@ static target_ulong remove_hpte(CPUPPCState *env, target_ulong ptex,
}
hpte = env->external_htab + (ptex * HASH_PTE_SIZE_64);
- while (!lock_hpte(hpte, HPTE_V_HVLOCK)) {
- /* We have no real concurrency in qemu soft-emulation, so we
- * will never actually have a contested lock */
- assert(0);
- }
v = ldq_p(hpte);
r = ldq_p(hpte + (HASH_PTE_SIZE_64/2));
@@ -205,16 +182,13 @@ static target_ulong remove_hpte(CPUPPCState *env, target_ulong ptex,
if ((v & HPTE_V_VALID) == 0 ||
((flags & H_AVPN) && (v & ~0x7fULL) != avpn) ||
((flags & H_ANDCOND) && (v & avpn) != 0)) {
- stq_p(hpte, v & ~HPTE_V_HVLOCK);
- assert(!(ldq_p(hpte) & HPTE_V_HVLOCK));
return REMOVE_NOT_FOUND;
}
- *vp = v & ~HPTE_V_HVLOCK;
+ *vp = v;
*rp = r;
stq_p(hpte, 0);
rb = compute_tlbie_rb(v, r, ptex);
ppc_tlb_invalidate_one(env, rb);
- assert(!(ldq_p(hpte) & HPTE_V_HVLOCK));
return REMOVE_SUCCESS;
}
@@ -324,19 +298,12 @@ static target_ulong h_protect(CPUPPCState *env, sPAPREnvironment *spapr,
}
hpte = env->external_htab + (pte_index * HASH_PTE_SIZE_64);
- while (!lock_hpte(hpte, HPTE_V_HVLOCK)) {
- /* We have no real concurrency in qemu soft-emulation, so we
- * will never actually have a contested lock */
- assert(0);
- }
v = ldq_p(hpte);
r = ldq_p(hpte + (HASH_PTE_SIZE_64/2));
if ((v & HPTE_V_VALID) == 0 ||
((flags & H_AVPN) && (v & ~0x7fULL) != avpn)) {
- stq_p(hpte, v & ~HPTE_V_HVLOCK);
- assert(!(ldq_p(hpte) & HPTE_V_HVLOCK));
return H_NOT_FOUND;
}
@@ -350,8 +317,7 @@ static target_ulong h_protect(CPUPPCState *env, sPAPREnvironment *spapr,
ppc_tlb_invalidate_one(env, rb);
stq_p(hpte + (HASH_PTE_SIZE_64/2), r);
/* Don't need a memory barrier, due to qemu's global lock */
- stq_p(hpte, v & ~HPTE_V_HVLOCK);
- assert(!(ldq_p(hpte) & HPTE_V_HVLOCK));
+ stq_p(hpte, v);
return H_SUCCESS;
}