[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v2] x86/ucode: Refresh raw CPU policy after microcode load
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Thu, 4 May 2023 12:00:07 +0100
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=Kf6e6xuLsE0l5KJi49O5tulDMMCfKntruNGAkxmvoEY=; b=avE7O3nyofZMUqu5yyc/gCmd0u0nsGHeQMsMaiyrMbWHjOLlx8gsdnDpYZUZJLucSOIafst0yGtPTIhd3pijPxwj5BW9NrJlVEFTXK01Jg54/Ahuynr23I3ltukYkAnSgId6Dl+DHPfAHI/7m9st8URB2sH9+ZQIQ1miulJeVv5HQiwtFh4jmNYAMiG/Xz/pM/n7mYuSHXrbTk49HwsNQ9k+b0DIKyyNbEiNVXsidlMGj+bl8XRNmbiWXfRb6cgMi5iDUHCgrGJWQPqL/40IPp0Ziz+MUc+HgO21f/RjyZSoPY6FG0/nQx7zxkycBe1mxYT3Fk4C8OVCKII3F/N/Eg==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Qrk8bSQHTzdzlHYqqbQsxXSS+YV8LOYSk4miGAJzizONwQS8JcSCgKBeey0CrViFXVaGYgMMIpEiiNxx2Pw5D+c9fHW/7QLdeYNa5fKwqr9e10e4Cl2Weuu1sTgTEfPRh4bMCw7dk8SkN+9w7VxchmQs9AdGZiad6f9ZvCkrjCx6medDX9D98f4sYBMu2asChGsXyBUZs+xLOAxTxVlglsFkWOTjaYXpKXF2QW95eWzbmSOQ6+KyDssbFJ/V6DYf1OE/RuHMJINCWXXpT4jgN+C73TOUN/ErBL3U+wPp6IlVw2tqHqTdXmYFIj2XuNfrkl4wVsyEf9Rl/oYkOZcDJw==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com;
- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Thu, 04 May 2023 11:00:42 +0000
- Ironport-data: A9a23:pUq2oK5/MYKorbHwjBWTBwxRtBXGchMFZxGqfqrLsTDasY5as4F+v mEZXWGEP/iDMWr9eNF2Ot/n9B4DvMTXz4RhTwBl/iFjHi5G8cbLO4+Ufxz6V8+wwm8vb2o8t plDNYOQRCwQZiWBzvt4GuG59RGQ7YnRGvynTraCYnsrLeNdYH9JoQp5nOIkiZJfj9G8Agec0 fv/uMSaM1K+s9JOGjt8B5mr9VU+7ZwehBtC5gZlPa0T4AeH/5UoJMl3yZ+ZfiOQrrZ8RoZWd 86bpJml82XQ+QsaC9/Nut4XpWVTH9Y+lSDX4pZnc/DKbipq/0Te4Y5iXBYoUm9Fii3hojxE4 I4lWapc6+seFvakdOw1C3G0GszlVEFM0OevzXOX6aR/w6BaGpdFLjoH4EweZOUlFuhL7W5m1 OU7JQpOMzy5g++E+uPmUfJJueoRI5y+VG8fkikIITDxK98DGMiGb4CUoNhS0XE3m9xEGuvYa 4wBcz1zYR/cYhpJfFAKFJY5m+TujX76G9FagAvN+exrvC6OnEooiOKF3Nn9I7RmQe18mEqCq 32A1GP+GhwAb/SUyCaf82LqjejK9c/+cNtLTOfoqaEz0DV/wEQeLy8ZDXedkMKYk3ynC/54F XUS6BQx+P1aGEuDC4OVsweDiG6JuFsQVsRdF8U+6RqR0ezE7gCBHG8GQzVdLts8u6ceRzYny 1uIlNPBHiF0vfueTnf13qiQhSO/P24SN2BqWMMfZQ4M4t2mrIRtiBvKF45nCPTs1oezHizsy TeXqiR4n68UkcMAy6S8+xbAni6ooZ/KCAUy4207Q16Y0++wX6b9D6TA1LQRxa8owFqxJrVZg EU5pg==
- Ironport-hdrordr: A9a23:0eVjXaq46fcsqMRpJDudUKcaV5ujLNV00zEX/kB9WHVpm5Oj5q eTdaUgpHvJYWgqKRQdcIi7Sdu9qLbnhNdICYl4B8bZYOCUghrcEGgC1/qj/9SEIVzTygcz79 YfT0ETMqyJMbE+t7eI3ODaKadi/DDkytHYuQ629R4EJm0EBdACnmEJczp3CncXeOAFP+tIKH P23Ls7m9PUQwVpUi3NPAh4YwGsnayxqHo7CSR2ZSIP2U2igS6l4qP9CDi0mi4EVTlC260v/A H+4kbED5GYwrSGI1LnpjTuB1s/oqqh9vJzQOi3zuQFIDTljQilIKxnRr25pTgw5M2/9Vowl9 HIghE4e+B+8WnYcG2ZqQbkn1CI6kdy11bSjXujxVfzq83wQzw3T+JHmIJiaxPcr2Ywod1m16 pP/mSB875aFwnJkijR78XBEztqik23i3w/lvN7tQ0EbaIuLJtq6aAP9kJcF5kNWAr89YAcCe FrSPrR4f5HGGnqI0ww6gNUoeCEbzAWJFOrU0ICssua33x9h3Zi1XYVw8QZgzMp6I89Y4Ms3Z WXDo1Y0JV1CuMGZ6N0A+kMBeGtDHbWfB7KOGWOZXz6CaA8PW7XoZKf2sRn2AiTQu1c8HIOou WRbLoYjx9tR6vWM7zQ4HSfyGGcfI2/NQ6dh/22qaIJ+MypeFIsWRfzDGzG2PHQ18n3OferEM pa4vptcrnexFvVaMF0NkXFKu5vwFklIZQoU4UAKgqzSjSiEPyligQtGMyja4YFVwxUBl8Wbx M4LW/ODfQF02TucnL0gB+Uc2/xeyXEjLhNOZmfwsxW4IUBNooJixMShEiy++uMJDEqiN0aQG JOZI7C1o62oGmo8X2N1WVmPRJBEl1YiY+QeE9ilEs2FwfRWZYn/+6yU0xz41erYiJea+++Km RijmUyxIbyC7Sx4GQfN/KLW1j2s5PXzEj6Z6v1XsW4lO7YklRRNOdxZER8eD+7YSCdsTwa4F t+VA==
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04/05/2023 11:47 am, Roger Pau Monné wrote:
> On Thu, May 04, 2023 at 11:26:07AM +0100, Andrew Cooper wrote:
>> Loading microcode can cause new features to appear. This has happened
>> routinely since Spectre/Meltdown, and even the presence of new status bits
>> can
>> sometimes mean the administrator has no further actions to perform.
>>
>> Conversely, loading microcode can occasionally cause features to disappear.
>> As with livepatching, it is very much the administrators responsibility to
>> confirm that a late microcode load is safe on the intended system before
>> rolling it out in production.
>>
>> Refresh the raw CPU policy after late microcode load appears to have done
>> something, so xen-cpuid can reflect the updated state of the system.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks.
> I'm not fully sure it's worth calling calculate_raw_cpu_policy() if
> updated != nr_cores, as it's possible the current CPU where the policy
> is regenerated hasn't been updated.
As said previously, updated != nr_cores may exist in principle, but it
is not a corner case we should care about.
If the system really is asymmetric after a late load, then it is
probably not long for the world. There is nothing Xen can do to recover.
It is awkward that we're not on the BSP when collecting. I think that
part of the logic didn't survive the rebase over switching to
stop-machine. I'll add it to the gitlab ticket of minor ucode work,
because it's not the end of the world.
~Andrew
|
