Re: [PATCH v5 1/3] x86/iommu: remove regions not to be mapped

From: Jan Beulich <jbeulich@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Paul Durrant <paul@xen.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v5 1/3] x86/iommu: remove regions not to be mapped
Date: Thu, 25 Jan 2024 12:13:01 +0100	[thread overview]
Message-ID: <ed221b62-0151-45ce-a88d-d7e2a9946136@suse.com> (raw)
In-Reply-To: <ZbIgE8exXDVicN8D@macbook>

On 25.01.2024 09:47, Roger Pau Monné wrote:
> On Thu, Jan 25, 2024 at 09:34:40AM +0100, Jan Beulich wrote:
>> On 24.01.2024 18:29, Roger Pau Monne wrote:
>>> --- a/xen/arch/x86/hvm/io.c
>>> +++ b/xen/arch/x86/hvm/io.c
>>> @@ -369,6 +369,22 @@ bool vpci_is_mmcfg_address(const struct domain *d, paddr_t addr)
>>>      return vpci_mmcfg_find(d, addr);
>>>  }
>>>  
>>> +int __hwdom_init vpci_subtract_mmcfg(const struct domain *d, struct rangeset *r)
>>> +{
>>> +    const struct hvm_mmcfg *mmcfg;
>>> +
>>> +    list_for_each_entry ( mmcfg, &d->arch.hvm.mmcfg_regions, next )
>>> +    {
>>> +        int rc = rangeset_remove_range(r, PFN_DOWN(mmcfg->addr),
>>> +                                       PFN_DOWN(mmcfg->addr + mmcfg->size - 1));
>>
>> Along the lines of this, ...
>>
>>> --- a/xen/arch/x86/setup.c
>>> +++ b/xen/arch/x86/setup.c
>>> @@ -2138,6 +2138,54 @@ int __hwdom_init xen_in_range(unsigned long mfn)
>>>      return 0;
>>>  }
>>>  
>>> +int __hwdom_init remove_xen_ranges(struct rangeset *r)
>>> +{
>>> +    paddr_t start, end;
>>> +    int rc;
>>> +
>>> +    /* S3 resume code (and other real mode trampoline code) */
>>> +    rc = rangeset_remove_range(r, PFN_DOWN(bootsym_phys(trampoline_start)),
>>> +                               PFN_DOWN(bootsym_phys(trampoline_end)) - 1);
>>
>> ... did you perhaps mean
>>
>>                                PFN_DOWN(bootsym_phys(trampoline_end) - 1));
>>
>> here (and then similarly below, except there the difference is benign I
>> think, for the labels being page-aligned)?
> 
> They are all page aligned, so I didn't care much,  but now that you
> point it might be safer to do the subtraction from the address instead
> of the frame number, just in case.

Hmm, no, for me neither trampoline_end nor trampoline_start are page
aligned. While bootsym_phys(trampoline_start) is, I don't think
bootsym_phys(trampoline_end) normally would be (it might only be by
coincidence).

Jan