Re: [PATCH] x86/boot: Fix early exception handling with CONFIG_PERF_COUNTERS

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/04/2020 09:35, Jan Beulich wrote:
> On 16.04.2020 10:19, Andrew Cooper wrote:
>> --- a/xen/arch/x86/x86_64/entry.S
>> +++ b/xen/arch/x86/x86_64/entry.S
>> @@ -679,7 +679,11 @@ handle_exception_saved:
>>  1:      movq  %rsp,%rdi
>>          movzbl UREGS_entry_vector(%rsp),%eax
>>          leaq  exception_table(%rip),%rdx
>> -        PERFC_INCR(exceptions, %rax, %rbx)
>> +#ifdef CONFIG_PERF_COUNTERS
>> +        lea   per_cpu__perfcounters(%rip), %rdi
>> +        add   STACK_CPUINFO_FIELD(per_cpu_offset)(%r14), %rdi
>> +        incl  ASM_PERFC_exceptions * 4(%rdi, %rax, 4)
>> +#endif
>>          mov   (%rdx, %rax, 8), %rdx
>>          INDIRECT_CALL %rdx
>>          mov   %r15, STACK_CPUINFO_FIELD(xen_cr3)(%r14)
>>
>>
>> If you're happy with that?
> I'm afraid I'm not - you can't use %rdi here, it already holds the
> called function's argument. I'd be fine with %rcx used instead.

Bah - serves me right for being lazy and not retesting.

%rcx it is.

~Andrew