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Re: [PATCH v3] x86emul: further correct 64-bit mode zero count repeated string insn handling
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 22 Jan 2025 14:29:25 +0100
- Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 22 Jan 2025 13:29:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.01.2025 11:23, Roger Pau Monné wrote:
> On Fri, Aug 04, 2023 at 07:58:21AM +0200, Jan Beulich wrote:
>> In an entirely different context I came across Linux commit 428e3d08574b
>> ("KVM: x86: Fix zero iterations REP-string"), which points out that
>> we're still doing things wrong: For one, there's no zero-extension at
>> all on AMD. And then while RCX is zero-extended from 32 bits uniformly
>> for all string instructions on newer hardware, RSI/RDI are only for MOVS
>> and STOS on the systems I have access to. (On an old family 0xf system
>> I've further found that for REP LODS even RCX is not zero-extended.)
>>
>> Fixes: 79e996a89f69 ("x86emul: correct 64-bit mode repeated string insn
>> handling with zero count")
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks. I'm uncertain though whether with concerns Andrew had voiced (maybe
just on irc/Matrix) I may go ahead and commit this. Andrew?
In any event - Oleksii, I guess I'd need a release ack here (or an indication
to defer to 4.21).
>> ---
>> Partly RFC for none of this being documented anywhere (and it partly
>> being model specific); inquiry pending.
>
> Did you get any reply on this?
No, and to be honest I also didn't have much hope I would get any reply.
Jan
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