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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id j38-20020a05600c48a600b003a3080eacb9sm13850227wmp.24.2022.08.01.04.32.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Aug 2022 04:32:25 -0700 (PDT) From: Vitaly Kuznetsov To: Andrei Vagin , Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Andrei Vagin , Sean Christopherson , Wanpeng Li , Jianfeng Tan , Adin Scannell , Konstantin Bogomolov , Etienne Perot Subject: Re: [PATCH 4/5] selftests/kvm/x86_64: set rax before vmcall In-Reply-To: <20220722230241.1944655-5-avagin@google.com> References: <20220722230241.1944655-1-avagin@google.com> <20220722230241.1944655-5-avagin@google.com> Date: Mon, 01 Aug 2022 13:32:24 +0200 Message-ID: <87y1w819o7.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Andrei Vagin writes: > 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 > Fixes: ac4a4d6de22e ("selftests: kvm: test enforcement of paravirtual cpuid features") > Signed-off-by: Andrei Vagin > --- > 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 ead7011ee8f6..5d85e1c021da 100644 > --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c > +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c > @@ -1422,7 +1422,7 @@ 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)); Wouldn't '"+a"(r)' instead of '"=a"(r)' suffice (assuming we also assing 'r' to 'nr' in the beginning, something like diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index ead7011ee8f6..fdd6554b94a1 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -1418,10 +1418,10 @@ bool set_cpuid(struct kvm_cpuid2 *cpuid, uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t a3) { - uint64_t r; + uint64_t r = nr; asm volatile("vmcall" - : "=a"(r) + : "+a"(r) : "b"(a0), "c"(a1), "d"(a2), "S"(a3)); return r; } -- Vitaly