Re: [RFC PATCH V2 06/18] x86/hyperv: Use vmmcall to implement hvcall in sev-snp enlightened guest

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On 12/14/2022 1:19 AM, Michael Kelley (LINUX) wrote:
From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Friday, November 18, 2022 7:46 PM

In sev-snp enlightened guest, hvcall needs to use vmmcall to trigger

What does "hvcall" refer to here?  Is this a Hyper-V hypercall, or just
a generic hypervisor call?

It's should be Hyper-V hypercall. Will make it accurate in the next
version. Thanks for reminder.


vmexit and notify hypervisor to handle hypercall request.

Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
  arch/x86/include/asm/mshyperv.h | 66 ++++++++++++++++++++++-----------
  1 file changed, 45 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 9b8c3f638845..28d5429e33c9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -45,16 +45,25 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
  	u64 hv_status;

  #ifdef CONFIG_X86_64
-	if (!hv_hypercall_pg)
-		return U64_MAX;
+	if (hv_isolation_type_en_snp()) {
+		__asm__ __volatile__("mov %4, %%r8\n"
+				"vmmcall"
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input_address)
+				:  "r" (output_address)
+				: "cc", "memory", "r8", "r9", "r10", "r11");
+	} else {
+		if (!hv_hypercall_pg)
+			return U64_MAX;

-	__asm__ __volatile__("mov %4, %%r8\n"
-			     CALL_NOSPEC
-			     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
-			       "+c" (control), "+d" (input_address)
-			     :  "r" (output_address),
-				THUNK_TARGET(hv_hypercall_pg)
-			     : "cc", "memory", "r8", "r9", "r10", "r11");
+		__asm__ __volatile__("mov %4, %%r8\n"
+				CALL_NOSPEC
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input_address)
+				:  "r" (output_address),
+					THUNK_TARGET(hv_hypercall_pg)
+				: "cc", "memory", "r8", "r9", "r10", "r11");
+	}
  #else
  	u32 input_address_hi = upper_32_bits(input_address);
  	u32 input_address_lo = lower_32_bits(input_address);
@@ -82,12 +91,18 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
  	u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;

  #ifdef CONFIG_X86_64
-	{
+	if (hv_isolation_type_en_snp()) {
+		__asm__ __volatile__(
+				"vmmcall"
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input1)
+				:: "cc", "r8", "r9", "r10", "r11");
+	} else {
  		__asm__ __volatile__(CALL_NOSPEC
-				     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
-				       "+c" (control), "+d" (input1)
-				     : THUNK_TARGET(hv_hypercall_pg)
-				     : "cc", "r8", "r9", "r10", "r11");
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input1)
+				: THUNK_TARGET(hv_hypercall_pg)
+				: "cc", "r8", "r9", "r10", "r11");

The above 4 lines appear to just have changes in indentation.  Maybe
there's value in having the same indentation as the new code you've
added, so I won't object if you want to keep the changes.

OK. Will update in the next version.


  	}
  #else
  	{
@@ -113,14 +128,21 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
  	u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;

  #ifdef CONFIG_X86_64
-	{
+	if (hv_isolation_type_en_snp()) {
  		__asm__ __volatile__("mov %4, %%r8\n"
-				     CALL_NOSPEC
-				     : "=a" (hv_status), ASM_CALL_CONSTRAINT,
-				       "+c" (control), "+d" (input1)
-				     : "r" (input2),
-				       THUNK_TARGET(hv_hypercall_pg)
-				     : "cc", "r8", "r9", "r10", "r11");
+				"vmmcall"
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input1)
+				: "r" (input2)
+				: "cc", "r8", "r9", "r10", "r11");
+	} else {
+		__asm__ __volatile__("mov %4, %%r8\n"
+				CALL_NOSPEC
+				: "=a" (hv_status), ASM_CALL_CONSTRAINT,
+				"+c" (control), "+d" (input1)
+				: "r" (input2),
+				THUNK_TARGET(hv_hypercall_pg)
+				: "cc", "r8", "r9", "r10", "r11");




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