Re: [Qemu-devel] [PULL] Memory core space reduction

[Avi Kivity <avi@redhat.com>]

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On 02/29/2012 12:53 PM, Avi Kivity wrote:
> I did get an abort with -enable-kvm, but that looks like the old issue,
> no?  Looking into it.
>
>

-- 
error compiling committee.c: too many arguments to function


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>From 4fa865c7086e2f287c91f4372df6eb5ddf40a48c Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@redhat.com>
Date: Wed, 29 Feb 2012 13:22:12 +0200
Subject: [PATCH] kvm: fix unaligned slots

kvm_set_phys_mem() may be passed sections that are not aligned to a page
boundary.  The current code simply brute-forces the alignment which leads
to an inconsistency and an abort().

Fix by aligning the start and the end of the section correctly, discarding
and unaligned head or tail.

This was triggered by a guest sizing a 64-bit BAR that is smaller than a page
with PCI_COMMAND_MEMORY enabled and the upper dword clear.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 kvm-all.c |   15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/kvm-all.c b/kvm-all.c
index 839b1dd..c58c77b 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -542,17 +542,26 @@ static void kvm_set_phys_mem(MemoryRegionSection *section, bool add)
     target_phys_addr_t start_addr = section->offset_within_address_space;
     ram_addr_t size = section->size;
     void *ram = NULL;
+    unsigned delta;
 
     /* kvm works in page size chunks, but the function may be called
        with sub-page size and unaligned start address. */
-    size = TARGET_PAGE_ALIGN(size);
-    start_addr = TARGET_PAGE_ALIGN(start_addr);
+    delta = TARGET_PAGE_ALIGN(size) - size;
+    if (delta > size) {
+        return;
+    }
+    start_addr += delta;
+    size -= delta;
+    size &= TARGET_PAGE_MASK;
+    if (!size || (start_addr & ~TARGET_PAGE_MASK)) {
+        return;
+    }
 
     if (!memory_region_is_ram(mr)) {
         return;
     }
 
-    ram = memory_region_get_ram_ptr(mr) + section->offset_within_region;
+    ram = memory_region_get_ram_ptr(mr) + section->offset_within_region + delta;
 
     while (1) {
         mem = kvm_lookup_overlapping_slot(s, start_addr, start_addr + size);
-- 
1.7.9