Re: [PATCH v6 8/9] target/i386/mshv: use hv-provided [0xD,1+2].EBX

["Doru Blânzeanu" <dblanzeanu@linux.microsoft.com>]

On Thu, Apr 16, 2026 at 02:11:15PM +0200, Magnus Kulke wrote:
> We cannot statically set the responses for CPUID[0xD,{1,2}].EBX, b/c
> those are dynamic, dependent on which features the guest enables.
> 
> Hence we mask EBX when registering answers for those subleaves at the
> hypervisor, which will result in the hypervisor providing us answers,
> considering XCR0 and XSS.
> 
> The reported size now reflects the field masks properly (without the
> mask they were 576 and 10728, which is wrong):
> 
> $ cpuid -l 0xd -s 0
> CPU 0:
>    XSAVE features (0xd/0):
>       XCR0 valid bit field mask               = 0x00000000000600e7
>       ...
>       bytes required by fields in XCR0        = 0x00002b00 (11008)
>       bytes required by XSAVE/XRSTOR area     = 0x00002b00 (11008)
> 
> $ cpuid -l 0xd -s 1
> CPU 0:
>    XSAVE features (0xd/1):
>       ...
>       SAVE area size in bytes                     = 0x000029c0 (10688)
>       IA32_XSS lower 32 bits valid bit field mask = 0x00001800
>       IA32_XSS upper 32 bits valid bit field mask = 0x00000000
> 
> Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> ---
>  target/i386/mshv/mshv-cpu.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
>

Reviewed-by: Doru Blânzeanu <dblanzeanu@linux.microsoft.com>