Re: dom0 PVH: Over-allocation for domain 0: 393217 > 393216

["Roger Pau Monné" <roger.pau@citrix.com>]

On 04/06/14 01:49, Mukesh Rathor wrote:
> On Tue, 3 Jun 2014 12:28:27 -0700
> Mukesh Rathor <mukesh.rathor@oracle.com> wrote:
> 
>> On Tue, 3 Jun 2014 14:11:17 +0200
>> Sander Eikelenboom <linux@eikelenboom.it> wrote:
>>
>>> Hi,
>>>
>>> I just tried booting with "dom0pvh" and found the following warnings
>>> (complete combined xl-dmesg/dmesg attached) which don't show up when
>>> booting without dom0pvh:
>>
>> Yeah, I see. I'm able to reproduce. Something about
>> dom0_mem=1536M,max:1536M ie, specifying max in there. Without it,
>> dom0_mem=1536M, its fine. You can do that to play around more while I
>> take a look.
> 
> Ok, I know whats going on. Basically, we are trying to populate the
> pfns removed due to punched holes in the e820, but because max is
> specified (same as initial ram), guest_physmap_add_page can't add.
> 
> This will be fixed by the e820 work that Roger and David Vrabel are 
> doing. Please keep an eye on the thread:
> 
> http://www.gossamer-threads.com/lists/xen/devel/332603

Hello,

I've been looking into this, and commented on David's patch:

http://lists.xenproject.org/archives/html/xen-devel/2014-06/msg00293.html

I'm also appending a modified version of patch 1, so you can apply it 
directly. It seems to work fine in all my test cases (no dom0_mem, 
dom0_mem=<mem> and dom0_mem=<mem>,max:<mem>).

---
commit f503c114f86d92036e1af4e4246550f15e85c4bb
Author: David Vrabel <david.vrabel@citrix.com>
Date:   Tue Jun 3 09:13:43 2014 +0200

    x86/xen: fix memory setup for PVH dom0
    
    Since af06d66ee32b (x86: fix setup of PVH Dom0 memory map) in Xen, PVH
    dom0 need only use the memory memory provided by Xen which has already
    setup all the correct holes.
    
    xen_memory_setup() then ends up being trivial for a PVH guest so
    introduce a new function (xen_auto_xlated_memory_setup()).
    
    Signed-off-by: David Vrabel <david.vrabel@citrix.com>
    Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 201d09a..4e7d2b7 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1536,7 +1536,10 @@ asmlinkage void __init xen_start_kernel(void)
 	if (!xen_pvh_domain())
 		pv_cpu_ops = xen_cpu_ops;
 
-	x86_init.resources.memory_setup = xen_memory_setup;
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		x86_init.resources.memory_setup = xen_auto_xlated_memory_setup;
+	else
+		x86_init.resources.memory_setup = xen_memory_setup;
 	x86_init.oem.arch_setup = xen_arch_setup;
 	x86_init.oem.banner = xen_banner;
 
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 0982233..e6e9df8 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -509,6 +509,34 @@ char * __init xen_memory_setup(void)
 }
 
 /*
+ * Machine specific memory setup for auto-translated guests.
+ */
+char * __init xen_auto_xlated_memory_setup(void)
+{
+	static struct e820entry map[E820MAX] __initdata;
+
+	struct xen_memory_map memmap;
+	int i;
+	int rc;
+
+	memmap.nr_entries = E820MAX;
+	set_xen_guest_handle(memmap.buffer, map);
+
+	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+	BUG_ON(rc);
+
+	sanitize_e820_map(map, ARRAY_SIZE(map), &memmap.nr_entries);
+
+	for (i = 0; i < memmap.nr_entries; i++)
+		e820_add_region(map[i].addr, map[i].size, map[i].type);
+
+	memblock_reserve(__pa(xen_start_info->mfn_list),
+		xen_start_info->pt_base - xen_start_info->mfn_list);
+
+	return "Xen";
+}
+
+/*
  * Set the bit indicating "nosegneg" library variants should be used.
  * We only need to bother in pure 32-bit mode; compat 32-bit processes
  * can have un-truncated segments, so wrapping around is allowed.
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 1cb6f4c..b371d18 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -34,6 +34,7 @@ extern unsigned long xen_max_p2m_pfn;
 void xen_set_pat(u64);
 
 char * __init xen_memory_setup(void);
+char * xen_auto_xlated_memory_setup(void);
 void __init xen_arch_setup(void);
 void xen_enable_sysenter(void);
 void xen_enable_syscall(void);