[PATCH for-10.0.x] Revert "target/i386: do not expose ARCH_CAPABILITIES on AMD CPU"

[PATCH for-10.0.x] Revert "target/i386: do not expose ARCH_CAPABILITIES on AMD CPU"

[Michael Tokarev]

This reverts commit 24778b1c7ee7aca9721ed4757b0e0df0c16390f7
(v10.0.2-66-g24778b1c7ee7) from the 10.0.x branch.

The problem is that the change makes qemu 10.0.x non-migratable
to subsequent qemu versions, since it requires introducing a new
machine type.

This revert re-introduces the problem with windows guests (which
is already fixed in windows but not in prior versions).
Details: https://gitlab.com/qemu-project/qemu/-/issues/3001

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 target/i386/kvm/kvm.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 70d6095be9..e88e5d17db 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -500,12 +500,8 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
          * Linux v4.17-v4.20 incorrectly return ARCH_CAPABILITIES on SVM hosts.
          * We can detect the bug by checking if MSR_IA32_ARCH_CAPABILITIES is
          * returned by KVM_GET_MSR_INDEX_LIST.
-         *
-         * But also, because Windows does not like ARCH_CAPABILITIES on AMD
-         * mcahines at all, do not show the fake ARCH_CAPABILITIES MSR that
-         * KVM sets up.
          */
-        if (!has_msr_arch_capabs || !(edx & CPUID_7_0_EDX_ARCH_CAPABILITIES)) {
+        if (!has_msr_arch_capabs) {
             ret &= ~CPUID_7_0_EDX_ARCH_CAPABILITIES;
         }
     } else if (function == 7 && index == 1 && reg == R_EAX) {
-- 
2.47.3

Re: [PATCH for-10.0.x] Revert "target/i386: do not expose ARCH_CAPABILITIES on AMD CPU"

[Zhao Liu]

On Wed, Oct 08, 2025 at 04:41:10PM +0300, Michael Tokarev wrote:
> Date: Wed, 8 Oct 2025 16:41:10 +0300
> From: Michael Tokarev <mjt@tls.msk.ru>
> Subject: [PATCH for-10.0.x] Revert "target/i386: do not expose
>  ARCH_CAPABILITIES on AMD CPU"
> X-Mailer: git-send-email 2.47.3
> 
> This reverts commit 24778b1c7ee7aca9721ed4757b0e0df0c16390f7
> (v10.0.2-66-g24778b1c7ee7) from the 10.0.x branch.
> 
> The problem is that the change makes qemu 10.0.x non-migratable
> to subsequent qemu versions, since it requires introducing a new
> machine type.
> 
> This revert re-introduces the problem with windows guests (which
> is already fixed in windows but not in prior versions).
> Details: https://gitlab.com/qemu-project/qemu/-/issues/3001
> 
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> ---
>  target/i386/kvm/kvm.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>