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target/ppc: Fix ordering of hash MMU accesses 

With mttcg, we can have MMU lookups happening at the same time
as the guest modifying the page tables.

Since the HPTEs of the hash table MMU contains two words (or
double worlds on 64-bit), we need to make sure we read them
in the right order, with the correct memory barrier.

Additionally, when using emulated SPAPR mode, the hypercalls
writing to the hash table must also perform the udpates in
the right order.

Note: This part is still not entirely correct

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190215170029.15641-7-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2019-02-15 18:00:23 +01:00 committed by David Gibson
parent 2819282dae
commit 3054b0ca4b
3 changed files with 31 additions and 2 deletions
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21
hw/ppc/spapr.c
View File

@ -1524,8 +1524,25 @@ static void spapr_store_hpte(PPCVirtualHypervisor *vhyp, hwaddr ptex,
if (!spapr->htab) {
kvmppc_write_hpte(ptex, pte0, pte1);
} else {
stq_p(spapr->htab + offset, pte0);
stq_p(spapr->htab + offset + HASH_PTE_SIZE_64 / 2, pte1);
if (pte0 & HPTE64_V_VALID) {
stq_p(spapr->htab + offset + HASH_PTE_SIZE_64 / 2, pte1);
/*
* When setting valid, we write PTE1 first. This ensures
* proper synchronization with the reading code in
* ppc_hash64_pteg_search()
*/
smp_wmb();
stq_p(spapr->htab + offset, pte0);
} else {
stq_p(spapr->htab + offset, pte0);
/*
* When clearing it we set PTE0 first. This ensures proper
* synchronization with the reading code in
* ppc_hash64_pteg_search()
*/
smp_wmb();
stq_p(spapr->htab + offset + HASH_PTE_SIZE_64 / 2, pte1);
}
}
}

6
target/ppc/mmu-hash32.c
View File

@ -319,6 +319,12 @@ static hwaddr ppc_hash32_pteg_search(PowerPCCPU *cpu, hwaddr pteg_off,
for (i = 0; i < HPTES_PER_GROUP; i++) {
pte0 = ppc_hash32_load_hpte0(cpu, pte_offset);
/*
* pte0 contains the valid bit and must be read before pte1,
* otherwise we might see an old pte1 with a new valid bit and
* thus an inconsistent hpte value
*/
smp_rmb();
pte1 = ppc_hash32_load_hpte1(cpu, pte_offset);
if ((pte0 & HPTE32_V_VALID)

6
target/ppc/mmu-hash64.c
View File

@ -507,6 +507,12 @@ static hwaddr ppc_hash64_pteg_search(PowerPCCPU *cpu, hwaddr hash,
}
for (i = 0; i < HPTES_PER_GROUP; i++) {
pte0 = ppc_hash64_hpte0(cpu, pteg, i);
/*
* pte0 contains the valid bit and must be read before pte1,
* otherwise we might see an old pte1 with a new valid bit and
* thus an inconsistent hpte value
*/
smp_rmb();
pte1 = ppc_hash64_hpte1(cpu, pteg, i);
/* This compares V, B, H (secondary) and the AVPN */