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[Qemu-devel] Re: [PATCH] qemu/pci: optimize pci config handling
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCH] qemu/pci: optimize pci config handling |
Date: |
Wed, 7 Oct 2009 15:48:53 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Wed, Oct 07, 2009 at 03:01:39PM +0200, Paolo Bonzini wrote:
> On 10/07/2009 02:33 PM, Michael S. Tsirkin wrote:
>> 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.
>
> You can even go a step further and save it only if something is actually
> being changed. Untested though.
I'm actively trying to get out of range-checking address.
What you porpose here is certainly more code than we had.
So why is this a good idea?
> Not-quite-signed-off-by: Paolo Bonzini <address@hidden>
>
> Paolo
> diff --git a/hw/pci.c b/hw/pci.c
> index 41e99a9..f9959fc 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -541,19 +541,26 @@ 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);
> - 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);
> + /* not efficient, but simple. If modifying the header, save it so we
> + can compare its contents later. */
> + if (addr < sizeof orig) {
> + memcpy(orig, d->config, sizeof orig);
> + }
> +
> + for(i = 0; i < l && addr+i < PCI_CONFIG_SPACE_SIZE; val >>= 8, ++i) {
> + uint8_t wmask = d->wmask[addr+i];
> + d->config[addr+i] = (d->config[addr+i] & ~wmask) | (val & wmask);
> + }
> +
> + if (addr < sizeof orig) {
> + if (memcmp(orig + PCI_BASE_ADDRESS_0, d->config +
> PCI_BASE_ADDRESS_0, 24)
> + || ((orig[PCI_COMMAND] ^ d->config[PCI_COMMAND])
> + & (PCI_COMMAND_MEMORY | PCI_COMMAND_IO)))
> + pci_update_mappings(d);
> }
> - if (memcmp(orig + PCI_BASE_ADDRESS_0, d->config + PCI_BASE_ADDRESS_0, 24)
> - || ((orig[PCI_COMMAND] ^ d->config[PCI_COMMAND])
> - & (PCI_COMMAND_MEMORY | PCI_COMMAND_IO)))
> - pci_update_mappings(d);
> }
>
> void pci_data_write(void *opaque, uint32_t addr, uint32_t val, int len)
[Qemu-devel] Re: [PATCH] qemu/pci: optimize pci config handling, Isaku Yamahata, 2009/10/07