by Tianyu Lan

[permalink] [raw]

Subject: Re: [RFC PATCH 5/12] HV: Add ghcb hvcall support for SNP VM

On 3/4/2021 1:21 AM, Vitaly Kuznetsov wrote:
> Tianyu Lan <[email protected]> writes:
>
>> From: Tianyu Lan <[email protected]>
>>
>> Hyper-V provides ghcb hvcall to handle VMBus
>> HVCALL_SIGNAL_EVENT and HVCALL_POST_MESSAGE
>> msg in SNP Isolation VM. Add such support.
>>
>> Signed-off-by: Tianyu Lan <[email protected]>
>> ---
>> arch/x86/hyperv/ivm.c | 69 +++++++++++++++++++++++++++++++++
>> arch/x86/include/asm/mshyperv.h | 1 +
>> drivers/hv/connection.c | 6 ++-
>> drivers/hv/hv.c | 8 +++-
>> 4 files changed, 82 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
>> index 4332bf7aaf9b..feaabcd151f5 100644
>> --- a/arch/x86/hyperv/ivm.c
>> +++ b/arch/x86/hyperv/ivm.c
>> @@ -14,8 +14,77 @@
>>
>> union hv_ghcb {
>> struct ghcb ghcb;
>> + struct {
>> + u64 hypercalldata[509];
>> + u64 outputgpa;
>> + union {
>> + union {
>> + struct {
>> + u32 callcode : 16;
>> + u32 isfast : 1;
>> + u32 reserved1 : 14;
>> + u32 isnested : 1;
>> + u32 countofelements : 12;
>> + u32 reserved2 : 4;
>> + u32 repstartindex : 12;
>> + u32 reserved3 : 4;
>> + };
>> + u64 asuint64;
>> + } hypercallinput;
>> + union {
>> + struct {
>> + u16 callstatus;
>> + u16 reserved1;
>> + u32 elementsprocessed : 12;
>> + u32 reserved2 : 20;
>> + };
>> + u64 asunit64;
>> + } hypercalloutput;
>> + };
>> + u64 reserved2;
>> + } hypercall;
>> } __packed __aligned(PAGE_SIZE);
>>
>> +u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size)
>> +{
>> + union hv_ghcb *hv_ghcb;
>> + void **ghcb_base;
>> + unsigned long flags;
>> +
>> + if (!ms_hyperv.ghcb_base)
>> + return -EFAULT;
>> +
>> + local_irq_save(flags);
>> + ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
>> + hv_ghcb = (union hv_ghcb *)*ghcb_base;
>> + if (!hv_ghcb) {
>> + local_irq_restore(flags);
>> + return -EFAULT;
>> + }
>> +
>> + memset(hv_ghcb, 0x00, HV_HYP_PAGE_SIZE);
>> + hv_ghcb->ghcb.protocol_version = 1;
>> + hv_ghcb->ghcb.ghcb_usage = 1;
>> +
>> + hv_ghcb->hypercall.outputgpa = (u64)output;
>> + hv_ghcb->hypercall.hypercallinput.asuint64 = 0;
>> + hv_ghcb->hypercall.hypercallinput.callcode = control;
>> +
>> + if (input_size)
>> + memcpy(hv_ghcb->hypercall.hypercalldata, input, input_size);
>> +
>> + VMGEXIT();
>> +
>> + hv_ghcb->ghcb.ghcb_usage = 0xffffffff;
>> + memset(hv_ghcb->ghcb.save.valid_bitmap, 0,
>> + sizeof(hv_ghcb->ghcb.save.valid_bitmap));
>> +
>> + local_irq_restore(flags);
>> +
>> + return hv_ghcb->hypercall.hypercalloutput.callstatus;
>> +}
>> +EXPORT_SYMBOL_GPL(hv_ghcb_hypercall);
>> +
>> void hv_ghcb_msr_write(u64 msr, u64 value)
>> {
>> union hv_ghcb *hv_ghcb;
>> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
>> index f624d72b99d3..c8f66d269e5b 100644
>> --- a/arch/x86/include/asm/mshyperv.h
>> +++ b/arch/x86/include/asm/mshyperv.h
>> @@ -274,6 +274,7 @@ void hv_sint_rdmsrl_ghcb(u64 msr, u64 *value);
>> void hv_signal_eom_ghcb(void);
>> void hv_ghcb_msr_write(u64 msr, u64 value);
>> void hv_ghcb_msr_read(u64 msr, u64 *value);
>> +u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
>>
>> #define hv_get_synint_state_ghcb(int_num, val) \
>> hv_sint_rdmsrl_ghcb(HV_X64_MSR_SINT0 + int_num, val)
>> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
>> index c83612cddb99..79bca653dce9 100644
>> --- a/drivers/hv/connection.c
>> +++ b/drivers/hv/connection.c
>> @@ -442,6 +442,10 @@ void vmbus_set_event(struct vmbus_channel *channel)
>>
>> ++channel->sig_events;
>>
>> - hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
>> + if (hv_isolation_type_snp())
>> + hv_ghcb_hypercall(HVCALL_SIGNAL_EVENT, &channel->sig_event,
>> + NULL, sizeof(u64));
>> + else
>> + hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
>
> vmbus_set_event() is a hotpath so I'd suggest we introduce a static
> branch instead of checking hv_isolation_type_snp() every time.
>

Good suggestion. Will add it in the next version. Thanks.