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[Qemu-devel] [PATCH] qemu/pci: optimize pci config handling

From: Michael S. Tsirkin
Subject: [Qemu-devel] [PATCH] qemu/pci: optimize pci config handling
Date: Wed, 7 Oct 2009 14:33:49 +0200
User-agent: Mutt/1.5.19 (2009-01-05)

There's no need to save all of config space before each config cycle:
just the 64 byte header is enough for our purposes.  This will become
more important as we add pci express support, which has 4K config space.

Signed-off-by: Michael S. Tsirkin <address@hidden>
Cc: Isaku Yamahata <address@hidden>

Isaku Yamahata, I think with this change, you can
increase the size of config space to 4K without
need for helper functions. Makes sense?

 hw/pci.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 41e99a9..5986937 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -541,11 +541,11 @@ uint32_t pci_default_read_config(PCIDevice *d,
 void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val, int l)
-    uint8_t orig[PCI_CONFIG_SPACE_SIZE];
+    uint8_t orig[PCI_CONFIG_HEADER_SIZE];
     int i;
     /* not efficient, but simple */
-    memcpy(orig, d->config, PCI_CONFIG_SPACE_SIZE);
+    memcpy(orig, d->config, sizeof orig);
     for(i = 0; i < l && addr < PCI_CONFIG_SPACE_SIZE; val >>= 8, ++i, ++addr) {
         uint8_t wmask = d->wmask[addr];
         d->config[addr] = (d->config[addr] & ~wmask) | (val & wmask);

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