[RFC][PATCH 03/34] x86/pci: Assume that clflush size is always provided

Dave Hansen
2024-02-22T18:39:31Z

The early boot code always sets _some_ clflush size. Use that fact
to avoid handling the case where it is not set.

There may have been a time when the Xen PV call in here way too
early. But it calls get_cpu_address_sizes() before calling here
now. It should also be safe.

Note: This series will eventually return sane defaults even very
early in boot. I believe this is safe now, but it becomes *really*
safe later on.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

b/arch/x86/pci/common.c | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)

diff -puN arch/x86/pci/common.c~x86-pci-clflush-size arch/x86/pci/common.c
--- a/arch/x86/pci/common.c~x86-pci-clflush-size 2024-02-22 10:08:49.356488521 -0800
+++ b/arch/x86/pci/common.c 2024-02-22 10:08:49.356488521 -0800
@@ -480,22 +480,9 @@ void pcibios_scan_root(int busnum)

void __init pcibios_set_cache_line_size(void)
{
- struct cpuinfo_x86 *c = &boot_cpu_data;
-
- /*
- * Set PCI cacheline size to that of the CPU if the CPU has reported it.
- * (For older CPUs that don't support cpuid, we se it to 32 bytes
- * It's also good for 386/486s (which actually have 16)
- * as quite a few PCI devices do not support smaller values.
- */
- if (c->x86_clflush_size > 0) {
- pci_dfl_cache_line_size = c->x86_clflush_size >> 2;
- printk(KERN_DEBUG "PCI: pci_cache_line_size set to %d bytes\n",
- pci_dfl_cache_line_size << 2);
- } else {
- pci_dfl_cache_line_size = 32 >> 2;
- printk(KERN_DEBUG "PCI: Unknown cacheline size. Setting to 32 bytes\n");
- }
+ pci_dfl_cache_line_size = boot_cpu_data.x86_clflush_size >> 2;
+ printk(KERN_DEBUG "PCI: pci_cache_line_size set to %d bytes\n",
+ pci_dfl_cache_line_size << 2);
}

int __init pcibios_init(void)
_