[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 7/9] vpci/header: program p2m with guest BAR view
On 09.09.2021 11:16, Oleksandr Andrushchenko wrote: > > On 09.09.21 11:26, Jan Beulich wrote: >> On 09.09.2021 08:13, Oleksandr Andrushchenko wrote: >>> On 06.09.21 17:51, Jan Beulich wrote: >>>> On 03.09.2021 12:08, Oleksandr Andrushchenko wrote: >>>>> @@ -37,12 +41,28 @@ static int map_range(unsigned long s, unsigned long >>>>> e, void *data, >>>>> unsigned long *c) >>>>> { >>>>> const struct map_data *map = data; >>>>> + gfn_t start_gfn; >>>>> int rc; >>>>> >>>>> for ( ; ; ) >>>>> { >>>>> unsigned long size = e - s + 1; >>>>> >>>>> + /* >>>>> + * Any BAR may have holes in its memory we want to map, e.g. >>>>> + * we don't want to map MSI regions which may be a part of that >>>>> BAR, >>>>> + * e.g. when a single BAR is used for both MMIO and MSI. >>>>> + * In this case MSI regions are subtracted from the mapping, but >>>>> + * map->start_gfn still points to the very beginning of the BAR. >>>>> + * So if there is a hole present then we need to adjust start_gfn >>>>> + * to reflect the fact of that substraction. >>>>> + */ >>>>> + start_gfn = gfn_add(map->start_gfn, s - mfn_x(map->start_mfn)); >>>> I may be missing something, but don't you need to adjust "size" then >>>> as well? >>> No, as range sets get consumed we have e and s updated accordingly, >>> so each time size represents the right value. >> It feels like something's wrong with the rangeset construction then: >> Either it represents _all_ holes (including degenerate ones at the >> start of end of a range), or none of them. > > The resulting range set only has the MMIOs in it. While constructing the > range set > we cut off MSI-X out of it (make holes). But finally it only has the ranges > that we > need to map/unmap. And then why is there a need to adjust start_gfn? Jan
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