[Qemu-devel] [PATCH qemu 2/2] ppc/spapr: Add "ibm, pa-features" property to the device-tree

[Alexey Kardashevskiy <aik@ozlabs.ru>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

LoPAPR defines a "ibm,pa-features" per-CPU device tree property which
describes extended features of the Processor Architecture.

This adds the property to the device tree. At the moment this is the
copy of what pHyp advertises except "I=1 (cache inhibited) Large Pages"
which is enabled for TCG and disabled when running under HV KVM host
with 4K system page size.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[aik: rebased, changed commit log, moved ci_large_pages initialization,
renamed pa_features arrays]
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/ppc/spapr.c              | 31 +++++++++++++++++++++++++++++++
 target-ppc/cpu.h            |  1 +
 target-ppc/kvm.c            |  7 +++++++
 target-ppc/translate_init.c |  1 +
 4 files changed, 40 insertions(+)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 3852ad1..21c1312 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -597,6 +597,24 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
     uint32_t vcpus_per_socket = smp_threads * smp_cores;
     uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
 
+    /* Note: we keep CI large pages off for now because a 64K capable guest
+     * provisioned with large pages might otherwise try to map a qemu
+     * framebuffer (or other kind of memory mapped PCI BAR) using 64K pages
+     * even if that qemu runs on a 4k host.
+     *
+     * We can later add this bit back when we are confident this is not
+     * an issue (!HV KVM or 64K host)
+     */
+    uint8_t pa_features_206[] = { 6, 0,
+        0xf6, 0x1f, 0xc7, 0x00, 0x80, 0xc0 };
+    uint8_t pa_features_207[] = { 24, 0,
+        0xf6, 0x1f, 0xc7, 0xc0, 0x80, 0xf0,
+        0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x80, 0x00,
+        0x80, 0x00, 0x80, 0x00, 0x80, 0x00 };
+    uint8_t *pa_features;
+    size_t pa_size;
+
     _FDT((fdt_setprop_cell(fdt, offset, "reg", index)));
     _FDT((fdt_setprop_string(fdt, offset, "device_type", "cpu")));
 
@@ -662,6 +680,19 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
                           page_sizes_prop, page_sizes_prop_size)));
     }
 
+    /* Do the ibm,pa-features property, adjust it for ci-large-pages */
+    if (env->mmu_model == POWERPC_MMU_2_06) {
+        pa_features = pa_features_206;
+        pa_size = sizeof(pa_features_206);
+    } else /* env->mmu_model == POWERPC_MMU_2_07 */ {
+        pa_features = pa_features_207;
+        pa_size = sizeof(pa_features_207);
+    }
+    if (env->ci_large_pages) {
+        pa_features[3] |= 0x20;
+    }
+    _FDT((fdt_setprop(fdt, offset, "ibm,pa-features", pa_features, pa_size)));
+
     _FDT((fdt_setprop_cell(fdt, offset, "ibm,chip-id",
                            cs->cpu_index / vcpus_per_socket)));
 
diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 69d8cf6..b34aed6 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -1073,6 +1073,7 @@ struct CPUPPCState {
     uint64_t insns_flags2;
 #if defined(TARGET_PPC64)
     struct ppc_segment_page_sizes sps;
+    bool ci_large_pages;
 #endif
 
 #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 7671ae7..0c59f7f 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -414,6 +414,13 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
     /* Convert to QEMU form */
     memset(&env->sps, 0, sizeof(env->sps));
 
+    /* If we have HV KVM, we need to forbid CI large pages if our
+     * host page size is smaller than 64K.
+     */
+    if (smmu_info.flags & KVM_PPC_PAGE_SIZES_REAL) {
+        env->ci_large_pages = getpagesize() >= 0x10000;
+    }
+
     /*
      * XXX This loop should be an entry wide AND of the capabilities that
      *     the selected CPU has with the capabilities that KVM supports.
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 2adbb63..4934c80 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -7864,6 +7864,7 @@ static void init_proc_book3s_64(CPUPPCState *env, int version)
         gen_spr_book3s_ids(env);
         gen_spr_amr(env);
         gen_spr_book3s_purr(env);
+        env->ci_large_pages = true;
         break;
     default:
         g_assert_not_reached();
-- 
2.5.0.rc3