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Re: [Xen-devel] [PATCH] xen/pv: Add PV specific legacy_pic struct to expose legacy IRQs.


  • To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>, Jennifer Herbert <jennifer.herbert@xxxxxxxxxx>, "x86@xxxxxxxxxx" <x86@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>
  • From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
  • Date: Wed, 27 Mar 2019 11:02:28 -0400
  • Autocrypt: addr=boris.ostrovsky@xxxxxxxxxx; prefer-encrypt=mutual; keydata= mQINBFH8CgsBEAC0KiOi9siOvlXatK2xX99e/J3OvApoYWjieVQ9232Eb7GzCWrItCzP8FUV PQg8rMsSd0OzIvvjbEAvaWLlbs8wa3MtVLysHY/DfqRK9Zvr/RgrsYC6ukOB7igy2PGqZd+M MDnSmVzik0sPvB6xPV7QyFsykEgpnHbvdZAUy/vyys8xgT0PVYR5hyvhyf6VIfGuvqIsvJw5 C8+P71CHI+U/IhsKrLrsiYHpAhQkw+Zvyeml6XSi5w4LXDbF+3oholKYCkPwxmGdK8MUIdkM d7iYdKqiP4W6FKQou/lC3jvOceGupEoDV9botSWEIIlKdtm6C4GfL45RD8V4B9iy24JHPlom woVWc0xBZboQguhauQqrBFooHO3roEeM1pxXjLUbDtH4t3SAI3gt4dpSyT3EvzhyNQVVIxj2 FXnIChrYxR6S0ijSqUKO0cAduenhBrpYbz9qFcB/GyxD+ZWY7OgQKHUZMWapx5bHGQ8bUZz2 SfjZwK+GETGhfkvNMf6zXbZkDq4kKB/ywaKvVPodS1Poa44+B9sxbUp1jMfFtlOJ3AYB0WDS Op3d7F2ry20CIf1Ifh0nIxkQPkTX7aX5rI92oZeu5u038dHUu/dO2EcuCjl1eDMGm5PLHDSP 0QUw5xzk1Y8MG1JQ56PtqReO33inBXG63yTIikJmUXFTw6lLJwARAQABtDNCb3JpcyBPc3Ry b3Zza3kgKFdvcmspIDxib3Jpcy5vc3Ryb3Zza3lAb3JhY2xlLmNvbT6JAjgEEwECACIFAlH8 CgsCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEIredpCGysGyasEP/j5xApopUf4g 9Fl3UxZuBx+oduuw3JHqgbGZ2siA3EA4bKwtKq8eT7ekpApn4c0HA8TWTDtgZtLSV5IdH+9z JimBDrhLkDI3Zsx2CafL4pMJvpUavhc5mEU8myp4dWCuIylHiWG65agvUeFZYK4P33fGqoaS VGx3tsQIAr7MsQxilMfRiTEoYH0WWthhE0YVQzV6kx4wj4yLGYPPBtFqnrapKKC8yFTpgjaK jImqWhU9CSUAXdNEs/oKVR1XlkDpMCFDl88vKAuJwugnixjbPFTVPyoC7+4Bm/FnL3iwlJVE qIGQRspt09r+datFzPqSbp5Fo/9m4JSvgtPp2X2+gIGgLPWp2ft1NXHHVWP19sPgEsEJXSr9 tskM8ScxEkqAUuDs6+x/ISX8wa5Pvmo65drN+JWA8EqKOHQG6LUsUdJolFM2i4Z0k40BnFU/ kjTARjrXW94LwokVy4x+ZYgImrnKWeKac6fMfMwH2aKpCQLlVxdO4qvJkv92SzZz4538az1T m+3ekJAimou89cXwXHCFb5WqJcyjDfdQF857vTn1z4qu7udYCuuV/4xDEhslUq1+GcNDjAhB nNYPzD+SvhWEsrjuXv+fDONdJtmLUpKs4Jtak3smGGhZsqpcNv8nQzUGDQZjuCSmDqW8vn2o hWwveNeRTkxh+2x1Qb3GT46uuQINBFH8CgsBEADGC/yx5ctcLQlB9hbq7KNqCDyZNoYu1HAB Hal3MuxPfoGKObEktawQPQaSTB5vNlDxKihezLnlT/PKjcXC2R1OjSDinlu5XNGc6mnky03q yymUPyiMtWhBBftezTRxWRslPaFWlg/h/Y1iDuOcklhpr7K1h1jRPCrf1yIoxbIpDbffnuyz kuto4AahRvBU4Js4sU7f/btU+h+e0AcLVzIhTVPIz7PM+Gk2LNzZ3/on4dnEc/qd+ZZFlOQ4 KDN/hPqlwA/YJsKzAPX51L6Vv344pqTm6Z0f9M7YALB/11FO2nBB7zw7HAUYqJeHutCwxm7i BDNt0g9fhviNcJzagqJ1R7aPjtjBoYvKkbwNu5sWDpQ4idnsnck4YT6ctzN4I+6lfkU8zMzC gM2R4qqUXmxFIS4Bee+gnJi0Pc3KcBYBZsDK44FtM//5Cp9DrxRQOh19kNHBlxkmEb8kL/pw XIDcEq8MXzPBbxwHKJ3QRWRe5jPNpf8HCjnZz0XyJV0/4M1JvOua7IZftOttQ6KnM4m6WNIZ 2ydg7dBhDa6iv1oKdL7wdp/rCulVWn8R7+3cRK95SnWiJ0qKDlMbIN8oGMhHdin8cSRYdmHK kTnvSGJNlkis5a+048o0C6jI3LozQYD/W9wq7MvgChgVQw1iEOB4u/3FXDEGulRVko6xCBU4 SQARAQABiQIfBBgBAgAJBQJR/AoLAhsMAAoJEIredpCGysGyfvMQAIywR6jTqix6/fL0Ip8G jpt3uk//QNxGJE3ZkUNLX6N786vnEJvc1beCu6EwqD1ezG9fJKMl7F3SEgpYaiKEcHfoKGdh 30B3Hsq44vOoxR6zxw2B/giADjhmWTP5tWQ9548N4VhIZMYQMQCkdqaueSL+8asp8tBNP+TJ PAIIANYvJaD8xA7sYUXGTzOXDh2THWSvmEWWmzok8er/u6ZKdS1YmZkUy8cfzrll/9hiGCTj u3qcaOM6i/m4hqtvsI1cOORMVwjJF4+IkC5ZBoeRs/xW5zIBdSUoC8L+OCyj5JETWTt40+lu qoqAF/AEGsNZTrwHJYu9rbHH260C0KYCNqmxDdcROUqIzJdzDKOrDmebkEVnxVeLJBIhYZUd t3Iq9hdjpU50TA6sQ3mZxzBdfRgg+vaj2DsJqI5Xla9QGKD+xNT6v14cZuIMZzO7w0DoojM4 ByrabFsOQxGvE0w9Dch2BDSI2Xyk1zjPKxG1VNBQVx3flH37QDWpL2zlJikW29Ws86PHdthh Fm5PY8YtX576DchSP6qJC57/eAAe/9ztZdVAdesQwGb9hZHJc75B+VNm4xrh/PJO6c1THqdQ 19WVJ+7rDx3PhVncGlbAOiiiE3NOFPJ1OQYxPKtpBUukAlOTnkKE6QcA4zckFepUkfmBV1wM Jg6OxFYd01z+a+oL
  • Cc: Juergen Gross <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 27 Mar 2019 14:57:05 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 3/25/19 10:40 AM, Paul Durrant wrote:
>> -----Original Message-----
>> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf Of 
>> Jennifer Herbert
>> Sent: 25 March 2019 14:24
>> To: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>; x86@xxxxxxxxxx; 
>> xen-devel@xxxxxxxxxxxxxxxxxxxx;
>> linux-kernel@xxxxxxxxxxxxxxx
>> Cc: Juergen Gross <jgross@xxxxxxxx>; Stefano Stabellini 
>> <sstabellini@xxxxxxxxxx>; Ingo Molnar
>> <mingo@xxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>; H. Peter Anvin 
>> <hpa@xxxxxxxxx>; Thomas Gleixner
>> <tglx@xxxxxxxxxxxxx>
>> Subject: Re: [Xen-devel] [PATCH] xen/pv: Add PV specific legacy_pic struct 
>> to expose legacy IRQs.
>>
>>
>>
>> On 21/03/19 17:49, Jennifer Herbert wrote:
>>>
>>> On 19/03/19 23:06, Boris Ostrovsky wrote:
>>>> On 3/19/19 4:02 PM, Jennifer Herbert wrote:
>>>>> The ACPI tables doesn't always contain all IRQs for legacy devices
>>>>> such as RTC.  Since no PIC controller is visible for a PV linux guest,
>>>>> under Xen, legacy_pic currently defaults to the null_legacy_pic - with
>>>>> reports no legacy IRQs.  Since the commit "rtc: cmos: Do not assume
>>>>> irq 8 for rtc when there are no legacy irqs" by Hans de Goede
>>>>> (commit id: a1e23a42f1bdc00e32fc4869caef12e4e6272f26), the rtc now
>>>>> incorrectly decides it has no irq it can use, for some hardware.
>>>>>
>>>>> This patch rectifies the problem by providing a xen legacy_pic
>>>>> struct, which is much like the null_legacy_pic except that it
>>>>> reports NR_IRQS_LEGACY irqs.
>>>> I assume this is for dom0?
>>>>
>>>> Could there be the same problem with PVH dom0? (and if yes then this
>>>> should probably go into arch/x86/xen/enlighten.c).
>>>>
>>>> -boris
>>>>
>>> I am doing this to fix a problem with dom0.  DomU doesn't seem to have
>>> an RTC, and so it is unaffected.
>>>
>>> I'm not familiar with PVH, but have now done some experiments. The RTC
>>> on PVH seems broken - but not quite in the same way as PV. More
>>> research is needed, however simply doing the same trick I did with PV
>>> will not fix the issue.
>>>
>>> I'll look further into it.
>>>
>> The same problem does exist with PVH - however its worse with the
>> presence of the IO-APIC, as with my patch it tries to set up with IRQ,
>> and fails.  I'm not sure how would be best to deal with this.
>> However, the RTC seems broken even for machines without the ACPI omission.
>> I can see fixing it for just PV doesn't seem too nice, but unsure how to
>> fix this for PVH.  I'm open to suggestions, but otherwise I'll put this
>> on hold.
> AFAICT from the code in libxl__arch_domain_prepare_config(), PVH domains 
> don't get an RTC, just a local APIC.
>


That's true for domU but not for PVH dom0 I believe. Roger?

-boris

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