Re: [RFC PATCH V3 13/16] x86/sev: Add Check of #HV event in path

[Tianyu Lan <ltykernel@gmail.com>]

On 3/9/2023 12:18 AM, Gupta, Pankaj wrote:
> On 3/1/2023 12:11 PM, Gupta, Pankaj wrote:
>> On 1/22/2023 3:46 AM, Tianyu Lan wrote:

>>> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
>>> index a8862a2eff67..fe5e5e41433d 100644
>>> --- a/arch/x86/kernel/sev.c
>>> +++ b/arch/x86/kernel/sev.c
>>> @@ -179,6 +179,45 @@ void noinstr __sev_es_ist_enter(struct pt_regs 
>>> *regs)
>>>       this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], new_ist);
>>>   }
>>> +static void do_exc_hv(struct pt_regs *regs)
>>> +{
>>> +    /* Handle #HV exception. */
>>> +}
>>> +
>>> +void check_hv_pending(struct pt_regs *regs)
>>> +{
>>> +    if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
>>> +        return;
>>> +
>>> +    if ((regs->flags & X86_EFLAGS_IF) == 0)
>>> +        return;
>>
>> Will this return and prevent guest from executing NMI's
>> while irqs are disabled?
> 
> I think we need to handle NMI's even when irqs are disabled.
> 

Yes, nice catch!

> As we reset "no_further_signal" in hv_raw_handle_exception()
> and return from check_hv_pending() when irqs are disabled, this
> can result in loss/delay of NMI event?

Will fix this in the next version.

Thanks.