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[Xen-devel] xen/arm: Alternative start of day cache coherency



Julien,

I wonder if the following is any better than the current stuff in
staging for the issue you are seeing with BSD at start of day? Can you
try it please.

It has survived >1000 bootloops on Midway and >50 on Mustang, both are
still going.

It basically does a cache clean on all RAM mapped in the p2m. Anything
in the cache is either the result of an earlier scrub of the page or
something toolstack just wrote, so there is no need to be concerned
about clean vs. invalidate -- clean is always correct.

This should ensure that the guest has no dirty pages when it starts.
This nobbles the HCR_DC based stuff, too since it is no longer
necessary. This avoids concerns about guests which enable MMU before
caches.

It contains debug BUG()s in various trap locations to trap if the guest
experiences any incoherence and has lots of other debugging left in etc.
(and hacks wrt prototypes not in headers)

Ian.

diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index e1d1bec..60c3091 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -48,6 +48,14 @@ int xc_domain_create(xc_interface *xch,
     return 0;
 }
 
+int xc_domain_cacheflush(xc_interface *xch, uint32_t domid)
+{
+    DECLARE_DOMCTL;
+    domctl.cmd = XEN_DOMCTL_cacheflush;
+    domctl.domain = (domid_t)domid;
+    domctl.u.cacheflush.start_mfn = 0;
+    return do_domctl(xch, &domctl);
+}
 
 int xc_domain_pause(xc_interface *xch,
                     uint32_t domid)
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 13f816b..43dae5c 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -453,6 +453,7 @@ int xc_domain_create(xc_interface *xch,
                      xen_domain_handle_t handle,
                      uint32_t flags,
                      uint32_t *pdomid);
+int xc_domain_cacheflush(xc_interface *xch, uint32_t domid);
 
 
 /* Functions to produce a dump of a given domain
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index a604cd8..55c86f0 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -1364,7 +1364,10 @@ static void domain_create_cb(libxl__egc *egc,
     STATE_AO_GC(cdcs->dcs.ao);
 
     if (!rc)
+    {
         *cdcs->domid_out = domid;
+        xc_domain_cacheflush(CTX->xch, domid);
+    }
 
     libxl__ao_complete(egc, ao, rc);
 }
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 635a9a4..2edd09d 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -475,7 +475,8 @@ int vcpu_initialise(struct vcpu *v)
         return rc;
 
     v->arch.sctlr = SCTLR_GUEST_INIT;
-    v->arch.default_cache = true;
+    //v->arch.default_cache = true;
+    v->arch.default_cache = false;
 
     /*
      * By default exposes an SMP system with AFF0 set to the VCPU ID
diff --git a/xen/arch/arm/domctl.c b/xen/arch/arm/domctl.c
index 546e86b..9e3b37d 100644
--- a/xen/arch/arm/domctl.c
+++ b/xen/arch/arm/domctl.c
@@ -11,12 +11,24 @@
 #include <xen/sched.h>
 #include <xen/hypercall.h>
 #include <public/domctl.h>
+#include <xen/guest_access.h>
+
+extern long p2m_cache_flush(struct domain *d, xen_pfn_t *start_mfn);
 
 long arch_do_domctl(struct xen_domctl *domctl, struct domain *d,
                     XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
 {
     switch ( domctl->cmd )
     {
+    case XEN_DOMCTL_cacheflush:
+    {
+        long rc = p2m_cache_flush(d, &domctl->u.cacheflush.start_mfn);
+        if ( __copy_to_guest(u_domctl, domctl, 1) )
+            rc = -EFAULT;
+
+        return rc;
+    }
+
     default:
         return subarch_do_domctl(domctl, d, u_domctl);
     }
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 85ca330..f35ed57 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -228,15 +228,26 @@ enum p2m_operation {
     ALLOCATE,
     REMOVE,
     RELINQUISH,
+    CACHEFLUSH,
 };
 
+static void do_one_cacheflush(paddr_t mfn)
+{
+    void *v = map_domain_page(mfn);
+
+    flush_xen_dcache_va_range(v, PAGE_SIZE);
+
+    unmap_domain_page(v);
+}
+
 static int create_p2m_entries(struct domain *d,
                      enum p2m_operation op,
                      paddr_t start_gpaddr,
                      paddr_t end_gpaddr,
                      paddr_t maddr,
                      int mattr,
-                     p2m_type_t t)
+                     p2m_type_t t,
+                     xen_pfn_t *last_mfn)
 {
     int rc;
     struct p2m_domain *p2m = &d->arch.p2m;
@@ -381,18 +392,42 @@ static int create_p2m_entries(struct domain *d,
                     count++;
                 }
                 break;
+            case CACHEFLUSH:
+                {
+                    if ( !pte.p2m.valid || !p2m_is_ram(pte.p2m.type) )
+                    {
+                        count++;
+                        break;
+                    }
+
+                    count += 0x10;
+
+                    do_one_cacheflush(pte.p2m.base);
+                }
+                break;
         }
 
+        if ( last_mfn )
+            *last_mfn = addr >> PAGE_SHIFT;
+
         /* Preempt every 2MiB (mapped) or 32 MiB (unmapped) - arbitrary */
-        if ( op == RELINQUISH && count >= 0x2000 )
+        switch ( op )
         {
-            if ( hypercall_preempt_check() )
+        case RELINQUISH:
+        case CACHEFLUSH:
+            if (count >= 0x2000 && hypercall_preempt_check() )
             {
                 p2m->next_gfn_to_relinquish = addr >> PAGE_SHIFT;
                 rc = -EAGAIN;
                 goto out;
             }
             count = 0;
+            break;
+        case INSERT:
+        case ALLOCATE:
+        case REMOVE:
+            /* No preemption */
+            break;
         }
 
         /* Got the next page */
@@ -439,7 +474,7 @@ int p2m_populate_ram(struct domain *d,
                      paddr_t end)
 {
     return create_p2m_entries(d, ALLOCATE, start, end,
-                              0, MATTR_MEM, p2m_ram_rw);
+                              0, MATTR_MEM, p2m_ram_rw, NULL);
 }
 
 int map_mmio_regions(struct domain *d,
@@ -448,7 +483,7 @@ int map_mmio_regions(struct domain *d,
                      paddr_t maddr)
 {
     return create_p2m_entries(d, INSERT, start_gaddr, end_gaddr,
-                              maddr, MATTR_DEV, p2m_mmio_direct);
+                              maddr, MATTR_DEV, p2m_mmio_direct, NULL);
 }
 
 int guest_physmap_add_entry(struct domain *d,
@@ -460,7 +495,7 @@ int guest_physmap_add_entry(struct domain *d,
     return create_p2m_entries(d, INSERT,
                               pfn_to_paddr(gpfn),
                               pfn_to_paddr(gpfn + (1 << page_order)),
-                              pfn_to_paddr(mfn), MATTR_MEM, t);
+                              pfn_to_paddr(mfn), MATTR_MEM, t, NULL);
 }
 
 void guest_physmap_remove_page(struct domain *d,
@@ -470,7 +505,7 @@ void guest_physmap_remove_page(struct domain *d,
     create_p2m_entries(d, REMOVE,
                        pfn_to_paddr(gpfn),
                        pfn_to_paddr(gpfn + (1<<page_order)),
-                       pfn_to_paddr(mfn), MATTR_MEM, p2m_invalid);
+                       pfn_to_paddr(mfn), MATTR_MEM, p2m_invalid, NULL);
 }
 
 int p2m_alloc_table(struct domain *d)
@@ -622,7 +657,28 @@ int relinquish_p2m_mapping(struct domain *d)
                               pfn_to_paddr(p2m->next_gfn_to_relinquish),
                               pfn_to_paddr(p2m->max_mapped_gfn),
                               pfn_to_paddr(INVALID_MFN),
-                              MATTR_MEM, p2m_invalid);
+                              MATTR_MEM, p2m_invalid, NULL);
+}
+
+long p2m_cache_flush(struct domain *d, xen_pfn_t *start_mfn)
+{
+    struct p2m_domain *p2m = &d->arch.p2m;
+
+    printk("dom%d p2m cache flush from mfn %"PRI_xen_pfn" RELIN %lx\n",
+           d->domain_id, *start_mfn, p2m->next_gfn_to_relinquish);
+
+    *start_mfn = MAX(*start_mfn, p2m->next_gfn_to_relinquish);
+
+    printk("dom%d p2m cache flush: %"PRIpaddr"-%"PRIpaddr"\n",
+           d->domain_id,
+           pfn_to_paddr(*start_mfn),
+           pfn_to_paddr(p2m->max_mapped_gfn));
+
+    return create_p2m_entries(d, CACHEFLUSH,
+                              pfn_to_paddr(*start_mfn),
+                              pfn_to_paddr(p2m->max_mapped_gfn),
+                              pfn_to_paddr(INVALID_MFN),
+                              MATTR_MEM, p2m_invalid, start_mfn);
 }
 
 unsigned long gmfn_to_mfn(struct domain *d, unsigned long gpfn)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 48a6fcc..546f7ce 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1283,6 +1283,7 @@ static void advance_pc(struct cpu_user_regs *regs, union 
hsr hsr)
 
 static void update_sctlr(struct vcpu *v, uint32_t val)
 {
+    BUG();
     /*
      * If MMU (SCTLR_M) is now enabled then we must disable HCR.DC
      * because they are incompatible.
@@ -1628,6 +1629,7 @@ static void do_trap_instr_abort_guest(struct 
cpu_user_regs *regs,
                                       union hsr hsr)
 {
     register_t addr = READ_SYSREG(FAR_EL2);
+    BUG();
     inject_iabt_exception(regs, addr, hsr.len);
 }
 
@@ -1683,6 +1685,8 @@ static void do_trap_data_abort_guest(struct cpu_user_regs 
*regs,
     }
 
 bad_data_abort:
+    show_execution_state(regs);
+    panic("DABT");
     inject_dabt_exception(regs, info.gva, hsr.len);
 }
 
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 91f01fa..d7b22c3 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -885,6 +885,13 @@ struct xen_domctl_set_max_evtchn {
 typedef struct xen_domctl_set_max_evtchn xen_domctl_set_max_evtchn_t;
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_set_max_evtchn_t);
 
+struct xen_domctl_cacheflush {
+    /* Updated for progress */
+    xen_pfn_t start_mfn;
+};
+typedef struct xen_domctl_cacheflush xen_domctl_cacheflush_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_cacheflush_t);
+
 struct xen_domctl {
     uint32_t cmd;
 #define XEN_DOMCTL_createdomain                   1
@@ -954,6 +961,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_setnodeaffinity               68
 #define XEN_DOMCTL_getnodeaffinity               69
 #define XEN_DOMCTL_set_max_evtchn                70
+#define XEN_DOMCTL_cacheflush                    71
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
@@ -1012,6 +1020,7 @@ struct xen_domctl {
         struct xen_domctl_set_max_evtchn    set_max_evtchn;
         struct xen_domctl_gdbsx_memio       gdbsx_guest_memio;
         struct xen_domctl_set_broken_page_p2m set_broken_page_p2m;
+        struct xen_domctl_cacheflush        cacheflush;
         struct xen_domctl_gdbsx_pauseunp_vcpu gdbsx_pauseunp_vcpu;
         struct xen_domctl_gdbsx_domstatus   gdbsx_domstatus;
         uint8_t                             pad[128];



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