[PATCH 0/1] MR8591: ntdll: Fill EnabledFeatures before return.

[Bernhard Übelacker (＠bernhardu)]

Followup to 03039ab2ee.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=58335

If I observed it right we currently leave `init_xstate_features` on older computers with EnabledFeatures being zero.
This leads in `__wine_syscall_dispatcher` to getting the xsave64 getting
called with "$rax = 0x0", therefore e.g. xmm6 gets not saved to the stack.
But later e.g. xmm6 gets restored from stack in `__wine_syscall_dispatcher` (see [](https://gitlab.winehq.org/wine/wine/-/blob/wine-10.12/dlls/ntdll/unix/signal...))

[PATCH 1/1] ntdll: Fill EnabledFeatures before return.

[Bernhard Übelacker]

From: Bernhard Übelacker

Followup to 03039ab2ee.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=58335
---
 dlls/ntdll/unix/system.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/ntdll/unix/system.c b/dlls/ntdll/unix/system.c
index e486da40691..e8758a3df6d 100644
--- a/dlls/ntdll/unix/system.c
+++ b/dlls/ntdll/unix/system.c
@@ -436,10 +436,10 @@ static void init_xstate_features( XSTATE_CONFIGURATION *xstate )
     TRACE( "XSAVE details %#x, %#x, %#x, %#x.\n", regs[0], regs[1], regs[2], regs[3] );
     supported_mask = ((ULONG64)regs[3] << 32) | regs[0];
     supported_mask &= do_xgetbv(0) & supported_features;
-    if (!(supported_mask >> 2)) return;

xstate->EnabledFeatures = (1 << XSTATE_LEGACY_FLOATING_POINT) | (1 << XSTATE_LEGACY_SSE) | supported_mask;
     xstate->EnabledVolatileFeatures = xstate->EnabledFeatures;
+    if (!(supported_mask >> 2)) return;
     xstate->AllFeatureSize = regs[1];

do_cpuid( 0x0000000d, 1, regs );

[PATCH 0/1] MR8591: Draft: ntdll: Fill EnabledFeatures before return.

[Dmitry Timoshkov (＠dmitry)]

Limited testing shows that this patch works.
What's the reason that it's marked as a draft?

[Bernhard Übelacker (＠bernhardu)]

On Fri Jul 18 11:26:43 2025 +0000, Dmitry Timoshkov wrote:
> Limited testing shows that this patch works.
> What's the reason that it's marked as a draft?

The first run of `test-linux-64` failed, so I wanted to check. But a second run succeeded, so I removed the draft state now.

[Alexandre Julliard (＠julliard)]

The real question is what does Windows do in this case?

[Bernhard Übelacker (＠bernhardu)]

On Fri Jul 18 23:21:29 2025 +0000, Alexandre Julliard wrote:
> The real question is what does Windows do in this case?

I don't know if I understand this right. Is the question how Windows fills the `xstate->EnabledFeatures`?

Then one would somehow need to run a Windows at such an ancient machine (I guess a VM could be sufficient with `-cpu host`?) and examine `user_shared_data.XState.EnabledFeatures` (and EnabledVolatileFeatures), by accessing it like in `test_user_shared_data`?