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Re: [PATCH] x86: restore semicolon after explicit DS prefix
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 9 Oct 2024 08:04:53 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 09 Oct 2024 06:05:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.10.2024 18:37, Andrew Cooper wrote:
> On 08/10/2024 5:00 pm, Jan Beulich wrote:
>> It's not unnecessary (as the earlier commit claimed): The integrated
>> assembler of Clang up to 11 complains about an "invalid operand for
>> instruction".
>>
>> Fixes: b42cf31d1165 ("x86: use alternative_input() in cache_flush()")
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> --- a/xen/arch/x86/flushtlb.c
>> +++ b/xen/arch/x86/flushtlb.c
>> @@ -286,7 +286,7 @@ void cache_flush(const void *addr, unsig
>> * + prefix than a clflush + nop, and hence the prefix is added
>> instead
>> * of letting the alternative framework fill the gap by appending
>> nops.
>> */
>> - alternative_input("ds clflush %[p]",
>> + alternative_input("ds; clflush %[p]",
>
> /* Clang-IAS < 12 needs the semicolon */ which can probably fit on the
> end of the line.
I've made it "Semicolon for Clang-IAS < 12" to actually fit on the line.
I wonder whether I can take the reply as "ack with that change"?
> Or we stop supporting such old versions of Clang/LLVM.
As indicated in reply to Roger's proposal, that would leave me without
any way to test with at least some Clang versions (unless I got into the
business of also building my own Clang binaries). IOW - I could live
with such a move, but I'd prefer us not to be overly aggressive there.
Jan
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