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Re: [PATCH v2 6/7] xen: allow mapping ACPI data using a different physical address


  • To: Juergen Gross <jgross@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 10 Sep 2024 10:54:44 +0200
  • 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: Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, "Rafael J. Wysocki" <rafael@xxxxxxxxxx>, Len Brown <lenb@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx
  • Delivery-date: Tue, 10 Sep 2024 08:54:51 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 10.09.2024 10:15, Juergen Gross wrote:
> On 20.08.24 11:56, Jan Beulich wrote:
>> On 20.08.2024 10:20, Juergen Gross wrote:
>>> @@ -838,6 +839,31 @@ void __init xen_do_remap_nonram(void)
>>>     pr_info("Remapped %u non-RAM page(s)\n", remapped);
>>>   }
>>>   
>>> +/*
>>> + * Xen variant of acpi_os_ioremap() taking potentially remapped non-RAM
>>> + * regions into acount.
>>> + * Any attempt to map an area crossing a remap boundary will produce a
>>> + * WARN() splat.
>>> + */
>>> +static void __iomem *xen_acpi_os_ioremap(acpi_physical_address phys,
>>> +                                    acpi_size size)
>>> +{
>>> +   unsigned int i;
>>> +   struct nonram_remap *remap = xen_nonram_remap;
>>
>> const (also in one of the functions in patch 5)?
> 
> Yes.
> 
>>
>>> +   for (i = 0; i < nr_nonram_remap; i++) {
>>> +           if (phys + size > remap->maddr &&
>>> +               phys < remap->maddr + remap->size) {
>>> +                   WARN_ON(phys < remap->maddr ||
>>> +                           phys + size > remap->maddr + remap->size);
>>> +                   phys = remap->paddr + phys - remap->maddr;
>>> +                   break;
>>> +           }
>>> +   }
>>> +
>>> +   return x86_acpi_os_ioremap(phys, size);
>>> +}
>>
>> At least this, perhaps also what patch 5 adds, likely wants to be limited
>> to the XEN_DOM0 case? Or else I wonder whether ...
>>
>>> @@ -850,6 +876,10 @@ void __init xen_add_remap_nonram(phys_addr_t maddr, 
>>> phys_addr_t paddr,
>>>             BUG();
>>>     }
>>>   
>>> +   /* Switch to the Xen acpi_os_ioremap() variant. */
>>> +   if (nr_nonram_remap == 0)
>>> +           acpi_os_ioremap = xen_acpi_os_ioremap;
>>
>> ... this would actually build when XEN_DOM0=n.
>>
>> I'm actually surprised there's no Dom0-only code section in this file,
>> where the new code could then simply be inserted.
> 
> I'd rather make this conditional on CONFIG_ACPI.

Oh, sure.

> Depending on how Xen tools will handle a PV-domain with "e820_host=1" this
> code might be important for domUs, too.

Right, if that's a possibility for PV (I thought that was a HVM-only thing,
yet maybe it really is precisely the other way around), then yes, DomU-s
may too need to cope with unexpected overlaps.

Jan



 


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