Re: [PATCH 2/2] selftests: KVM: Fix 'asm-operand-width' warnings in steal_time.c

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On 21/09/21 09:19, Andrew Jones wrote:
On Tue, Sep 21, 2021 at 01:01:20AM +0000, Oliver Upton wrote:
Building steal_time.c for arm64 with clang throws the following:

steal_time.c:130:22: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
           : "=r" (ret) : "r" (func), "r" (arg) :
                               ^
steal_time.c:130:34: error: value size does not match register size specified by the constraint and modifier [-Werror,-Wasm-operand-widths]
           : "=r" (ret) : "r" (func), "r" (arg) :
                                           ^

Silence by casting operands to 64 bits.

Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
---
  tools/testing/selftests/kvm/steal_time.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index ecec30865a74..eb75b31122c5 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -127,7 +127,7 @@ static int64_t smccc(uint32_t func, uint32_t arg)
  		"mov	x1, %2\n"
  		"hvc	#0\n"
  		"mov	%0, x0\n"
-	: "=r" (ret) : "r" (func), "r" (arg) :
+	: "=r" (ret) : "r" ((uint64_t)func), "r" ((uint64_t)arg) :

Actually, I think I'd rather fix this smccc implementation to match the
spec, which I think should be done like this

diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index ecec30865a74..7da957259ce4 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -118,12 +118,12 @@ struct st_time {
         uint64_t st_time;
  };
-static int64_t smccc(uint32_t func, uint32_t arg)
+static int64_t smccc(uint32_t func, uint64_t arg)
  {
         unsigned long ret;
asm volatile(
-               "mov    x0, %1\n"
+               "mov    w0, %w1\n"
                 "mov    x1, %2\n"
                 "hvc    #0\n"
                 "mov    %0, x0\n"


Agreed, can you send out a patch?  Thanks,

Paolo




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