Messages in this thread | | | Subject | Re: PATCH: Update disable_IO_APIC to use 8-bit destination field (X86_64) | From | Benjamin Romer <> | Date | Thu, 18 Jan 2007 09:58:14 -0500 |
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On Thu, 2007-01-18 at 13:30 +0530, Vivek Goyal wrote: > On Thu, Jan 18, 2007 at 12:10:55AM -0700, Eric W. Biederman wrote: > > Vivek Goyal <vgoyal@in.ibm.com> writes: > > > > > > Or how about making physical_dest field also 8bit like logical_dest field. > > > This will work both for 4bit and 8bit physical apic ids at the same time > > > code becomes more intutive and it is easier to know whether IOAPIC is being > > > put in physical or destination logical mode. > > > > Exactly what I was trying to suggest. > > > > Looking closer at the code I think it makes sense to just kill the union and > > stop the discrimination between physical and logical modes and just have a > > dest field in the structure. Roughly as you were suggesting at first. > > > > The reason we aren't bitten by this on a regular basis is the normal code > > path uses logical.logical_dest in both logical and physical modes. > > Which is a little confusing. > > > > Since there really isn't a distinction to be made we should just stop > > trying, which will make maintenance easier :) > > > > Currently there are several non-common case users of physical_dest > > that are probably bitten by this problem under the right > > circumstances. > > > > So I think we should just make the structure: > > > > struct IO_APIC_route_entry { > > __u32 vector : 8, > > delivery_mode : 3, /* 000: FIXED > > * 001: lowest prio > > * 111: ExtINT > > */ > > dest_mode : 1, /* 0: physical, 1: logical */ > > delivery_status : 1, > > polarity : 1, > > irr : 1, > > trigger : 1, /* 0: edge, 1: level */ > > mask : 1, /* 0: enabled, 1: disabled */ > > __reserved_2 : 15; > > > > __u32 __reserved_3 : 24, > > __dest : 8; > > } __attribute__ ((packed)); > > > > And fixup the users. This should keep us from getting bit by this bug > > in the future. Like when people start introducing support for more > > than 256 cores and the low 24bits start getting used. > > > > Or when someone new starts working on the code and thinks the fact > > the field name says logical we are actually using the apic in logical > > mode. > > This makes perfect sense to me. Ben, interested in providing a patch > for this? > > Thanks > Vivek
Sure! I'll fix it up and get a revised patch out as soon as I can. :)
-- Ben
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