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Re: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks to slot management

From: Jan Kiszka
Subject: Re: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks to slot management
Date: Wed, 29 Apr 2009 19:30:52 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv: Gecko/20080226 SUSE/ Thunderbird/ Mnenhy/

Hollis Blanchard wrote:
> On Wed, 2009-04-29 at 12:38 +0200, Jan Kiszka wrote:
>> Liu Yu-B13201 wrote:
>>>> -----Original Message-----
>>>> From: address@hidden 
>>>> [mailto:address@hidden 
>>>> On Behalf Of Jan Kiszka
>>>> Sent: Sunday, April 12, 2009 1:20 AM
>>>> To: address@hidden
>>>> Subject: [Qemu-devel] [PATCH 4/7] kvm: Add sanity checks to 
>>>> slot management
>>>> Fail loudly if we run out of memory slot.
>>>> Make sure that dirty log start/stop works with consistent 
>>>> memory regions
>>>> by reporting invalid parameters. This reveals several 
>>>> inconsistencies in
>>>> the vga code, patch to fix them follows later in this series.
>>>> And, for simplicity reasons, also catch and report unaligned memory
>>>> regions passed to kvm_set_phys_mem (KVM works on page basis).
>>> Commit d3f8d37fe2d0c24ec8bac9c94d5b0e2dc09c0d2a hurts kvm/powerpc
>>> The alignment check in kvm_set_phys_mem prevents pci controller and mpic 
>>> initializing mmio regions.
>> What is the alignment of those regions then? None? And do regions of
>> different types overlap even on the same page? Maybe the check reveals
>> some deeper conflict /wrt KVM. Can you point me to the involved code files?
> These PCI controllers make separate calls to
> cpu_register_physical_memory() for separate callbacks. Reading
> ppce500_pci_init(), for example:
> 0xe0008000 -> CFGADDR (4 bytes)
> 0xe0008004 -> CFGDATA (4 bytes)
> 0xe0008c00 -> other registers
> The loop in cpu_register_physical_memory_offset() handles "subpage"
> registration. However, kvm_set_phys_mem() is called outside that loop,
> so it gets the non-page-aligned addresses.

Half-blind shot:

diff --git a/kvm-all.c b/kvm-all.c
index 32cd636..c2c760e 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -583,6 +583,9 @@ void kvm_set_phys_mem(target_phys_addr_t start_addr,
     int err;

     if (start_addr & ~TARGET_PAGE_MASK) {
+        if (flags >= IO_MEM_UNASSIGNED) {
+            return;
+        }
         fprintf(stderr, "Only page-aligned memory slots supported\n");

If it works, it likely needs a cleaner approach to handle all cases.


Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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