[v4,1/2] kvm/cpuid: remove GuestPhysBits code.

Commit Message

Gerd Hoffmann March 13, 2024, 12:58 p.m. UTC

GuestPhysBits (cpuid leaf 80000008, eax[23:16]) is intended for software
use.  Physical CPUs do not set that field.  The current code which
propagates the host's GuestPhysBits to the guest's PhysBits does not
make sense.  Remove it.

Signed-off-by: Gerd Hoffmann <[e-mail]>
Reviewed-by: Xiaoyao Li <[e-mail]>
---
 arch/x86/kvm/cpuid.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

Patch

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index adba49afb5fe..3235254724cf 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1221,9 +1221,8 @@  static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->eax = entry->ebx = entry->ecx = 0;
 		break;
 	case 0x80000008: {
-		unsigned g_phys_as = (entry->eax >> 16) & 0xff;
-		unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U);
-		unsigned phys_as = entry->eax & 0xff;
+		unsigned int virt_as = max((entry->eax >> 8) & 0xff, 48U);
+		unsigned int phys_as;
 
 		/*
 		 * If TDP (NPT) is disabled use the adjusted host MAXPHYADDR as
@@ -1231,16 +1230,16 @@  static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		 * reductions in MAXPHYADDR for memory encryption affect shadow
 		 * paging, too.
 		 *
-		 * If TDP is enabled but an explicit guest MAXPHYADDR is not
-		 * provided, use the raw bare metal MAXPHYADDR as reductions to
-		 * the HPAs do not affect GPAs.
+		 * If TDP is enabled, use the raw bare metal MAXPHYADDR as
+		 * reductions to the HPAs do not affect GPAs.
 		 */
-		if (!tdp_enabled)
-			g_phys_as = boot_cpu_data.x86_phys_bits;
-		else if (!g_phys_as)
-			g_phys_as = phys_as;
+		if (!tdp_enabled) {
+			phys_as = boot_cpu_data.x86_phys_bits;
+		} else {
+			phys_as = entry->eax & 0xff;
+		}
 
-		entry->eax = g_phys_as | (virt_as << 8);
+		entry->eax = phys_as | (virt_as << 8);
 		entry->ecx &= ~(GENMASK(31, 16) | GENMASK(11, 8));
 		entry->edx = 0;
 		cpuid_entry_override(entry, CPUID_8000_0008_EBX);