diff mbox

[5/6] target-ppc: Remove hack for ppc_hash64_load_hpte*() with HV KVM

Message ID 1454638439-11938-6-git-send-email-david@gibson.dropbear.id.au
State New, archived
Headers show

Commit Message

David Gibson Feb. 5, 2016, 2:13 a.m. UTC
With HV KVM, the guest's hash page table (HPT) is managed by the kernel and
not directly accessible to QEMU.  This means that spapr->htab is NULL
and normally env->external_htab would also be NULL for each cpu.

However, that would cause ppc_hash64_load_hpte*() to do the wrong thing in
the few cases where QEMU does need to load entries from the in-kernel HPT.
Specifically, seeing external_htab is NULL, they would look for an HPT
within the guest's address space instead.

To stop that we have an ugly hack in the pseries machine type code to
set external htab to (void *)1 instead.

This patch removes that hack by having ppc_hash64_load_hpte*() explicitly
check kvmppc_kern_htab instead, which makes more sense.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 hw/ppc/spapr.c          | 7 -------
 target-ppc/mmu-hash64.h | 4 ++--
 2 files changed, 2 insertions(+), 9 deletions(-)

Comments

Alexey Kardashevskiy Feb. 8, 2016, 6:35 a.m. UTC | #1
On 02/05/2016 01:13 PM, David Gibson wrote:
> With HV KVM, the guest's hash page table (HPT) is managed by the kernel and
> not directly accessible to QEMU.  This means that spapr->htab is NULL
> and normally env->external_htab would also be NULL for each cpu.
>
> However, that would cause ppc_hash64_load_hpte*() to do the wrong thing in
> the few cases where QEMU does need to load entries from the in-kernel HPT.
> Specifically, seeing external_htab is NULL, they would look for an HPT
> within the guest's address space instead.
>
> To stop that we have an ugly hack in the pseries machine type code to
> set external htab to (void *)1 instead.
>
> This patch removes that hack by having ppc_hash64_load_hpte*() explicitly
> check kvmppc_kern_htab instead, which makes more sense.
>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

To my limited knowledge of kvmppc_kern_htab&co, this looks good.

Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>



> ---
>   hw/ppc/spapr.c          | 7 -------
>   target-ppc/mmu-hash64.h | 4 ++--
>   2 files changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d228375..77dd1b6 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1196,13 +1196,6 @@ static void spapr_cpu_reset(void *opaque)
>       env->spr[SPR_HIOR] = 0;
>
>       env->external_htab = (uint8_t *)spapr->htab;
> -    if (kvm_enabled() && !env->external_htab) {
> -        /*
> -         * HV KVM, set external_htab to 1 so our ppc_hash64_load_hpte*
> -         * functions do the right thing.
> -         */
> -        env->external_htab = (void *)1;
> -    }
>       env->htab_base = -1;
>       /*
>        * htab_mask is the mask used to normalize hash value to PTEG index.
> diff --git a/target-ppc/mmu-hash64.h b/target-ppc/mmu-hash64.h
> index ab0f86b..e7d9925 100644
> --- a/target-ppc/mmu-hash64.h
> +++ b/target-ppc/mmu-hash64.h
> @@ -102,7 +102,7 @@ static inline target_ulong ppc_hash64_load_hpte0(PowerPCCPU *cpu,
>       uint64_t addr;
>
>       addr = token + (index * HASH_PTE_SIZE_64);
> -    if (env->external_htab) {
> +    if (kvmppc_kern_htab || env->external_htab) {
>           return  ldq_p((const void *)(uintptr_t)addr);
>       } else {
>           return ldq_phys(CPU(cpu)->as, addr);


Out of curiosity - how does this work? ldq_p() reads from the userspace address


> @@ -116,7 +116,7 @@ static inline target_ulong ppc_hash64_load_hpte1(PowerPCCPU *cpu,
>       uint64_t addr;
>
>       addr = token + (index * HASH_PTE_SIZE_64) + HASH_PTE_SIZE_64/2;
> -    if (env->external_htab) {
> +    if (kvmppc_kern_htab || env->external_htab) {
>           return  ldq_p((const void *)(uintptr_t)addr);
>       } else {
>           return ldq_phys(CPU(cpu)->as, addr);
>
diff mbox

Patch

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d228375..77dd1b6 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1196,13 +1196,6 @@  static void spapr_cpu_reset(void *opaque)
     env->spr[SPR_HIOR] = 0;
 
     env->external_htab = (uint8_t *)spapr->htab;
-    if (kvm_enabled() && !env->external_htab) {
-        /*
-         * HV KVM, set external_htab to 1 so our ppc_hash64_load_hpte*
-         * functions do the right thing.
-         */
-        env->external_htab = (void *)1;
-    }
     env->htab_base = -1;
     /*
      * htab_mask is the mask used to normalize hash value to PTEG index.
diff --git a/target-ppc/mmu-hash64.h b/target-ppc/mmu-hash64.h
index ab0f86b..e7d9925 100644
--- a/target-ppc/mmu-hash64.h
+++ b/target-ppc/mmu-hash64.h
@@ -102,7 +102,7 @@  static inline target_ulong ppc_hash64_load_hpte0(PowerPCCPU *cpu,
     uint64_t addr;
 
     addr = token + (index * HASH_PTE_SIZE_64);
-    if (env->external_htab) {
+    if (kvmppc_kern_htab || env->external_htab) {
         return  ldq_p((const void *)(uintptr_t)addr);
     } else {
         return ldq_phys(CPU(cpu)->as, addr);
@@ -116,7 +116,7 @@  static inline target_ulong ppc_hash64_load_hpte1(PowerPCCPU *cpu,
     uint64_t addr;
 
     addr = token + (index * HASH_PTE_SIZE_64) + HASH_PTE_SIZE_64/2;
-    if (env->external_htab) {
+    if (kvmppc_kern_htab || env->external_htab) {
         return  ldq_p((const void *)(uintptr_t)addr);
     } else {
         return ldq_phys(CPU(cpu)->as, addr);