[Xen-devel] [PATCH v4 4/6] x86/PV: allow PV guests to have an emulated PIT

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

This fixes the fallout from the HVMlite series, that removed the emulated
PIT from PV(H) guests. Also, this patch forces the hardware domain to
always have an emulated PIT, regardless of whether the toolstack specified
one or not.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Changes since v3:
 - Allow PV guests to specify whether a PIT is needed or not.
 - Fix pv_pit_handler so it can deal with the fact that the PIT might not be
   present.

Changes since v2:
 - Force the emulated PIT to always be enabled for the hardware domain.
 - Change indentation of the valid set of emulation bitmaps check.
---
 xen/arch/x86/domain.c    | 5 ++++-
 xen/arch/x86/hvm/i8254.c | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index e70c125..b005fe0 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -542,8 +542,11 @@ int arch_domain_create(struct domain *d, unsigned int 
domcr_flags,
                    d->domain_id, config->emulation_flags);
             return -EINVAL;
         }
+        if ( is_hardware_domain(d) )
+            config->emulation_flags |= XEN_X86_EMU_PIT;
         if ( config->emulation_flags != 0 &&
-             (!is_hvm_domain(d) || config->emulation_flags != XEN_X86_EMU_ALL) 
)
+             (is_hvm_domain(d) ? (config->emulation_flags != XEN_X86_EMU_ALL) :
+                                 (config->emulation_flags != XEN_X86_EMU_PIT)) 
)
         {
             printk(XENLOG_G_ERR "d%d: Xen does not allow %s domain creation "
                    "with the current selection of emulators: %#x\n",
diff --git a/xen/arch/x86/hvm/i8254.c b/xen/arch/x86/hvm/i8254.c
index b517cd6..577b43c 100644
--- a/xen/arch/x86/hvm/i8254.c
+++ b/xen/arch/x86/hvm/i8254.c
@@ -568,6 +568,9 @@ int pv_pit_handler(int port, int data, int write)
         .data = data
     };
 
+    if ( !has_vpit(current->domain) )
+        return ~0;
+
     if ( is_hardware_domain(current->domain) && hwdom_pit_access(&ioreq) )
     {
         /* nothing to do */;
-- 
1.9.5 (Apple Git-50.3)


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