[PATCH 03/16] x86/intel: Drop the paddr_bits workaround for P4 Nocona/Prescott CPUs

Andrew Cooper posted 16 patches 2 weeks ago
[PATCH 03/16] x86/intel: Drop the paddr_bits workaround for P4 Nocona/Prescott CPUs
Posted by Andrew Cooper 2 weeks ago
These are 32bit CPUs only.  64bit support started with model 4 (Prescott-256).

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Julian Vetter <julian.vetter@vates.tech>
CC: Teddy Astie <teddy.astie@vates.tech>
CC: Kevin Lampis <kevin.lampis@citrix.com>

This ideally wants backporting to 4.20 along with the rest of the VFM cleanup
in order to support DMR/NVL, which ends with removing the x86_ prefixed names.
---
 xen/arch/x86/cpu/intel.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
index d585161dd32f..eec6ee763040 100644
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -335,11 +335,6 @@ static void cf_check early_init_intel(struct cpuinfo_x86 *c)
 	    bootsym(trampoline_misc_enable_off) & MSR_IA32_MISC_ENABLE_XD_DISABLE)
 		printk(KERN_INFO "re-enabled NX (Execute Disable) protection\n");
 
-	/* CPUID workaround for Intel 0F33/0F34 CPU */
-	if (boot_cpu_data.x86 == 0xF && boot_cpu_data.x86_model == 3 &&
-	    (boot_cpu_data.x86_mask == 3 || boot_cpu_data.x86_mask == 4))
-		paddr_bits = 36;
-
 	if (c == &boot_cpu_data) {
 		uint64_t misc_enable;
 
-- 
2.39.5


Re: [PATCH 03/16] x86/intel: Drop the paddr_bits workaround for P4 Nocona/Prescott CPUs
Posted by Andrew Cooper 1 week, 6 days ago
On 26/01/2026 5:53 pm, Andrew Cooper wrote:
> These are 32bit CPUs only.  64bit support started with model 4 (Prescott-256).

It turns out that this isn't true.  These CPUs did have Long Mode.

I'll need to rework this patch into a later one.

~Andrew