Re: [Xen-devel] [PATCH 1/2] VT-d: check all of an RMRR for being E820-reserved

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Feb 07, 2020 at 02:27:11PM +0100, Jan Beulich wrote:
> On 07.02.2020 13:20, Roger Pau Monné wrote:
> > On Thu, Feb 06, 2020 at 02:31:03PM +0100, Jan Beulich wrote:
> >> Checking just the first and last page is not sufficient (and redundant
> >> for single-page regions). As we don't need to care about IA64 anymore,
> >> use an x86-specific function to get this done without looping over each
> >> individual page.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >>
> >> --- a/xen/drivers/passthrough/vtd/dmar.c
> >> +++ b/xen/drivers/passthrough/vtd/dmar.c
> >> @@ -29,6 +29,7 @@
> >>  #include <xen/pci.h>
> >>  #include <xen/pci_regs.h>
> >>  #include <asm/atomic.h>
> >> +#include <asm/e820.h>
> >>  #include <asm/string.h>
> >>  #include "dmar.h"
> >>  #include "iommu.h"
> >> @@ -632,14 +633,11 @@ acpi_parse_one_rmrr(struct acpi_dmar_hea
> >>       * not properly represented in the system memory map and
> >>       * inform the user
> >>       */
> >> -    if ( (!page_is_ram_type(paddr_to_pfn(base_addr), RAM_TYPE_RESERVED)) 
> >> ||
> >> -         (!page_is_ram_type(paddr_to_pfn(end_addr), RAM_TYPE_RESERVED)) )
> >> -    {
> >> +    if ( !e820_all_mapped(base_addr, end_addr + 1, RAM_TYPE_RESERVED) )
> > 
> > Do you need to add one to the end?
> > 
> > The other user of e820_all_mapped seems to treat end as start + size
> > - 1, which makes me think the parameters to the function are an
> > inclusive range [start, end] and that's what's present in the RMRR
> > ACPI entries?
> 
> Well, it's the implementation of the function which matters. This
> one other caller is wrong afaict, and I've just sent a patch. The
> non-inclusiveness is also in line with Linux'es variant of the
> function (where we've got ours from originally, just that it has
> been renamed and slightly extended since then).

Thanks for fixing that other caller and clarifying the comment.

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

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