[RFC PATCH V3 05/11] HV: Add ghcb hvcall support for SNP VM

[Tianyu Lan <ltykernel@xxxxxxxxx>]

From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

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 <Tianyu.Lan@xxxxxxxxxxxxx>
---
 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 fd6dd804beef..e687fca68ba3 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -18,8 +18,77 @@
 
 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 eec7f3357d51..51dfbd040930 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -259,6 +259,7 @@ 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 311cd005b3be..186fd4c8acd4 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -445,6 +445,10 @@ 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);
 }
 EXPORT_SYMBOL_GPL(vmbus_set_event);
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 28faa8364952..03bcc831b034 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -97,7 +97,13 @@ int hv_post_message(union hv_connection_id connection_id,
        aligned_msg->payload_size = payload_size;
        memcpy((void *)aligned_msg->payload, payload, payload_size);
 
-       status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);
+       if (hv_isolation_type_snp())
+               status = hv_ghcb_hypercall(HVCALL_POST_MESSAGE,
+                               (void *)aligned_msg, NULL,
+                               sizeof(struct hv_input_post_message));
+       else
+               status = hv_do_hypercall(HVCALL_POST_MESSAGE,
+                               aligned_msg, NULL);
 
        /* Preemption must remain disabled until after the hypercall
         * so some other thread can't get scheduled onto this cpu and
-- 
2.25.1