Re: [PATCH] vmd: handle the reset control register at 0xcf9

Mike Larkin <[email protected]> writes:

> On Tue, Aug 25, 2026 at 09:10:28PM +0000, ssnf wrote:
>
> This seems pretty good. dv@, you ok with it too?

I think there are some issues...not sure the reset bits are right and
from my quick checking I think we need to implement reads of the
register. At least linux reads before it writes and I'm not sure the
consequence yet of not emulating that correctly.

I'll look at it more closely.

>
> -ml
>
>> ---
>>  usr.sbin/vmd/x86_vm.c | 20 ++++++++++++++------
>>  1 file changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/usr.sbin/vmd/x86_vm.c b/usr.sbin/vmd/x86_vm.c
>> index 1b5ade90f9b..bcb40a63d04 100644
>> --- a/usr.sbin/vmd/x86_vm.c
>> +++ b/usr.sbin/vmd/x86_vm.c
>> @@ -45,6 +45,10 @@ typedef uint8_t (*io_fn_t)(struct vm_run_params *);
>>
>>  #define LOWMEM_KB	576
>>  #define MAX_PORTS	65536
>> +#define RST_CNT  	0xcf9
>> +#define RST_CNT_SYS_RST	0x01
>> +#define RST_CNT_RST_CPU	0x02
>> +#define RST_CNT_RESET	(RST_CNT_SYS_RST | RST_CNT_RST_CPU)
>>
>>  io_fn_t	ioports_map[MAX_PORTS];
>>
>> @@ -52,7 +56,7 @@ int	 translate_gva(struct vm_exit*, uint64_t, uint64_t *, int);
>>
>>  static int	loadfile_bios(gzFile, off_t, struct vcpu_reg_state *);
>>  static int	vcpu_exit_eptviolation(struct vm_run_params *);
>> -static void	vcpu_exit_inout(struct vm_run_params *);
>> +static int	vcpu_exit_inout(struct vm_run_params *);
>>
>>  extern struct vmd_vm	*current_vm;
>>  extern int		 con_fd;
>> @@ -449,12 +453,16 @@ unpause_vm_md(struct vmd_vm *vm)
>>   * Parameters:
>>   *  vrp: vcpu run parameters containing guest state for this exit
>>   */
>> -void
>> +int
>>  vcpu_exit_inout(struct vm_run_params *vrp)
>>  {
>>  	struct vm_exit *vei = vrp->vrp_exit;
>>  	uint8_t intr = 0xFF;
>>
>> +	if (vei->vei.vei_dir == VEI_DIR_OUT &&
>> +	    vei->vei.vei_port == RST_CNT &&
>> +	    (vei->vei.vei_data & RST_CNT_RESET) == RST_CNT_RESET)
>> +		return (EAGAIN);
>>  	if (vei->vei.vei_rep || vei->vei.vei_string) {
>>  #ifdef MMIO_DEBUG
>>  		log_info("%s: %s%s%s %d-byte, enc=%d, data=0x%08x, port=0x%04x",
>> @@ -483,6 +491,7 @@ vcpu_exit_inout(struct vm_run_params *vrp)
>>
>>  	if (intr != 0xFF)
>>  		vcpu_assert_irq(vrp->vrp_vm_id, vrp->vrp_vcpu_id, intr);
>> +	return (0);
>>  }
>>
>>  /*
>> @@ -509,6 +518,7 @@ vcpu_exit(struct vm_run_params *vrp)
>>  {
>>  	int ret;
>>
>> +	ret = 0;
>>  	switch (vrp->vrp_exit_reason) {
>>  	case VMX_EXIT_INT_WINDOW:
>>  	case SVM_VMEXIT_VINTR:
>> @@ -528,12 +538,10 @@ vcpu_exit(struct vm_run_params *vrp)
>>  	case SVM_VMEXIT_NPF:
>>  	case VMX_EXIT_EPT_VIOLATION:
>>  		ret = vcpu_exit_eptviolation(vrp);
>> -		if (ret)
>> -			return (ret);
>>  		break;
>>  	case VMX_EXIT_IO:
>>  	case SVM_VMEXIT_IOIO:
>> -		vcpu_exit_inout(vrp);
>> +		ret = vcpu_exit_inout(vrp);
>>  		break;
>>  	case VMX_EXIT_HLT:
>>  	case SVM_VMEXIT_HLT:
>> @@ -547,7 +555,7 @@ vcpu_exit(struct vm_run_params *vrp)
>>  		log_debug("unknown exit reason 0x%x", vrp->vrp_exit_reason);
>>  	}
>>
>> -	return (0);
>> +	return (ret);
>>  }
>>
>>  /*
>> --
>> 2.51.0
>>