linux-kernel - [PATCH 5.15 541/779] selftests: kvm: set rax before vmcall

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Message-Id: <20220815180400.445087721@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 20:03:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andrei Vagin <avagin@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 541/779] selftests: kvm: set rax before vmcall

From: Andrei Vagin <avagin@...gle.com>

[ Upstream commit 281106f938d3daaea6f8b6723a8217a2a1ef6936 ]

kvm_hypercall has to place the hypercall number in rax.

Trace events show that kvm_pv_test doesn't work properly:
     kvm_pv_test-53132: kvm_hypercall: nr 0x0 a0 0x0 a1 0x0 a2 0x0 a3 0x0
     kvm_pv_test-53132: kvm_hypercall: nr 0x0 a0 0x0 a1 0x0 a2 0x0 a3 0x0
     kvm_pv_test-53132: kvm_hypercall: nr 0x0 a0 0x0 a1 0x0 a2 0x0 a3 0x0

With this change, it starts working as expected:
     kvm_pv_test-54285: kvm_hypercall: nr 0x5 a0 0x0 a1 0x0 a2 0x0 a3 0x0
     kvm_pv_test-54285: kvm_hypercall: nr 0xa a0 0x0 a1 0x0 a2 0x0 a3 0x0
     kvm_pv_test-54285: kvm_hypercall: nr 0xb a0 0x0 a1 0x0 a2 0x0 a3 0x0

Signed-off-by: Andrei Vagin <avagin@...gle.com>
Message-Id: <20220722230241.1944655-5-avagin@...gle.com>
Fixes: ac4a4d6de22e ("selftests: kvm: test enforcement of paravirtual cpuid features")
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/testing/selftests/kvm/lib/x86_64/processor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 46057079d8bb..4f1449fa9592 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1326,7 +1326,7 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
 
 	asm volatile("vmcall"
 		     : "=a"(r)
-		     : "b"(a0), "c"(a1), "d"(a2), "S"(a3));
+		     : "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));
 	return r;
 }
 
-- 
2.35.1