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From: David Gibson <david@gibson.dropbear.id.au>
To: peter.maydell@linaro.org
Cc: groug@kaod.org, qemu-ppc@nongnu.org, qemu-devel@nongnu.org,
	lvivier@redhat.com, David Gibson <david@gibson.dropbear.id.au>
Subject: [Qemu-devel] [PULL 11/15] spapr: Handle VMX/VSX presence as an spapr capability flag
Date: Wed,  3 Jan 2018 15:24:15 +1100	[thread overview]
Message-ID: <20180103042419.14520-12-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20180103042419.14520-1-david@gibson.dropbear.id.au>

We currently have some conditionals in the spapr device tree code to decide
whether or not to advertise the availability of the VMX (aka Altivec) and
VSX vector extensions to the guest, based on whether the guest cpu has
those features.

This can lead to confusion and subtle failures on migration, since it makes
a guest visible change based only on host capabilities.  We now have a
better mechanism for this, in spapr capabilities flags, which explicitly
depend on user options rather than host capabilities.

Rework the advertisement of VSX and VMX based on a new VSX capability.  We
no longer bother with a conditional for VMX support, because every CPU
that's ever been supported by the pseries machine type supports VMX.

NOTE: Some userspace distributions (e.g. RHEL7.4) already rely on
availability of VSX in libc, so using cap-vsx=off may lead to a fatal
SIGILL in init.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Greg Kurz <groug@kaod.org>
---
 hw/ppc/spapr.c         | 20 +++++++++++---------
 hw/ppc/spapr_caps.c    | 25 +++++++++++++++++++++++++
 include/hw/ppc/spapr.h |  3 +++
 3 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 86fc83f9c2..693dd6f7b3 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -557,14 +557,16 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
                           segs, sizeof(segs))));
     }
 
-    /* Advertise VMX/VSX (vector extensions) if available
-     *   0 / no property == no vector extensions
+    /* Advertise VSX (vector extensions) if available
      *   1               == VMX / Altivec available
-     *   2               == VSX available */
-    if (env->insns_flags & PPC_ALTIVEC) {
-        uint32_t vmx = (env->insns_flags2 & PPC2_VSX) ? 2 : 1;
-
-        _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", vmx)));
+     *   2               == VSX available
+     *
+     * Only CPUs for which we create core types in spapr_cpu_core.c
+     * are possible, and all of those have VMX */
+    if (spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
+        _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 2)));
+    } else {
+        _FDT((fdt_setprop_cell(fdt, offset, "ibm,vmx", 1)));
     }
 
     /* Advertise DFP (Decimal Floating Point) if available
@@ -3832,7 +3834,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
      */
     mc->numa_mem_align_shift = 28;
 
-    smc->default_caps = spapr_caps(0);
+    smc->default_caps = spapr_caps(SPAPR_CAP_VSX);
     spapr_caps_add_properties(smc, &error_abort);
 }
 
@@ -3914,7 +3916,7 @@ static void spapr_machine_2_11_class_options(MachineClass *mc)
     sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
 
     spapr_machine_2_12_class_options(mc);
-    smc->default_caps = spapr_caps(SPAPR_CAP_HTM);
+    smc->default_caps = spapr_caps(SPAPR_CAP_HTM | SPAPR_CAP_VSX);
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_11);
 }
 
diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
index cad40fe49a..7c855c67ad 100644
--- a/hw/ppc/spapr_caps.c
+++ b/hw/ppc/spapr_caps.c
@@ -57,6 +57,19 @@ static void cap_htm_allow(sPAPRMachineState *spapr, Error **errp)
     }
 }
 
+static void cap_vsx_allow(sPAPRMachineState *spapr, Error **errp)
+{
+    PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
+    CPUPPCState *env = &cpu->env;
+
+    /* Allowable CPUs in spapr_cpu_core.c should already have gotten
+     * rid of anything that doesn't do VMX */
+    g_assert(env->insns_flags & PPC_ALTIVEC);
+    if (!(env->insns_flags2 & PPC2_VSX)) {
+        error_setg(errp, "VSX support not available, try cap-vsx=off");
+    }
+}
+
 static sPAPRCapabilityInfo capability_table[] = {
     {
         .name = "htm",
@@ -65,6 +78,13 @@ static sPAPRCapabilityInfo capability_table[] = {
         .allow = cap_htm_allow,
         /* TODO: add cap_htm_disallow */
     },
+    {
+        .name = "vsx",
+        .description = "Allow Vector Scalar Extensions (VSX)",
+        .flag = SPAPR_CAP_VSX,
+        .allow = cap_vsx_allow,
+        /* TODO: add cap_vsx_disallow */
+    },
 };
 
 static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState *spapr,
@@ -81,6 +101,11 @@ static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState *spapr,
         caps.mask &= ~SPAPR_CAP_HTM;
     }
 
+    if (!ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_2_06,
+                          0, spapr->max_compat_pvr)) {
+        caps.mask &= ~SPAPR_CAP_VSX;
+    }
+
     return caps;
 }
 
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 5c85f39c3b..148a03d189 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -59,6 +59,9 @@ typedef enum {
 /* Hardware Transactional Memory */
 #define SPAPR_CAP_HTM               0x0000000000000001ULL
 
+/* Vector Scalar Extensions */
+#define SPAPR_CAP_VSX               0x0000000000000002ULL
+
 typedef struct sPAPRCapabilities sPAPRCapabilities;
 struct sPAPRCapabilities {
     uint64_t mask;
-- 
2.14.3

  parent reply	other threads:[~2018-01-03  4:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-03  4:24 [Qemu-devel] [PULL 00/15] ppc-for-2.12 queue 20180103 David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 01/15] target-ppc: optimize cmp translation David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 02/15] pseries: Update SLOF firmware image to qemu-slof-20171214 David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 03/15] sm501: Add panel hardware cursor registers also to read function David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 04/15] sm501: Add some more unimplemented registers David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 05/15] ppc4xx_i2c: Implement basic I2C functions David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 06/15] ppc/pnv: change powernv_ prefix to pnv_ for overall naming consistency David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 07/15] spapr: Capabilities infrastructure David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 08/15] spapr: Treat Hardware Transactional Memory (HTM) as an optional capability David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 09/15] spapr: Validate capabilities on migration David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 10/15] target/ppc: Clean up probing of VMX, VSX and DFP availability on KVM David Gibson
2018-01-03  4:24 ` David Gibson [this message]
2018-01-03  4:24 ` [Qemu-devel] [PULL 12/15] spapr: Handle Decimal Floating Point (DFP) as an optional capability David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 13/15] spapr_pci: use warn_report() David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 14/15] hw/ide: Emulate SiI3112 SATA controller David Gibson
2018-01-03  4:24 ` [Qemu-devel] [PULL 15/15] target/ppc: more use of the PPC_*() macros David Gibson

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