On 2025-05-21 20:00, Andrew Cooper wrote:
On 21/05/2025 3:36 pm, Andrew Cooper wrote:
diff --git a/xen/arch/x86/include/asm/msr.h
b/xen/arch/x86/include/asm/msr.h
index 0d3b1d637488..4c4f18b3a54d 100644
--- a/xen/arch/x86/include/asm/msr.h
+++ b/xen/arch/x86/include/asm/msr.h
@@ -69,20 +69,20 @@ static inline void wrmsr_ns(uint32_t msr, uint32_t
lo, uint32_t hi)
/* wrmsr with exception handling */
static inline int wrmsr_safe(unsigned int msr, uint64_t val)
{
- int rc;
- uint32_t lo, hi;
- lo = (uint32_t)val;
- hi = (uint32_t)(val >> 32);
-
- __asm__ __volatile__(
- "1: wrmsr\n2:\n"
- ".section .fixup,\"ax\"\n"
- "3: movl %5,%0\n; jmp 2b\n"
- ".previous\n"
- _ASM_EXTABLE(1b, 3b)
- : "=&r" (rc)
- : "c" (msr), "a" (lo), "d" (hi), "0" (0), "i" (-EFAULT));
- return rc;
+ uint32_t lo = val, hi = val >> 32;
+
+ asm_inline goto (
+ "1: wrmsr\n\t"
+ _ASM_EXTABLE(1b, %l[fault])
+ :
+ : "a" (lo), "c" (msr), "d" (hi)
+ :
+ : fault );
+
+ return 0;
+
+ fault:
+ return -EFAULT;
}
It turns out this is the first piece of Eclair-scanned code using asm
goto.
https://gitlab.com/xen-project/hardware/xen-staging/-/jobs/10108558677
(The run also contained an equivalent change to xsetbv())
We're getting R1.1 and R2.6 violations.
R1.1 complains about [STD.adrslabl] "label address" not being valid
C99.
R2.6 complains about unused labels.
I expect this means that Eclair doesn't know how to interpret asm
goto()
yet. The labels listed are reachable from inside the asm block.
From a qualification point of view, this allows for some extensive
optimisations dropping emitted code.
Hi Andrew,
R1.1 is easy to fix, I'll send a patch myself. On R2.6 you are probably
right. I suggest marking the rule not clean to unblock while we
investigate. It should not be hard to fix this FP.
Thanks,
Nicola
~Andrew
--
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253
