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Re: [PATCH v4 10/11] xen: modify page table construction
From: |
Daniel Kiper |
Subject: |
Re: [PATCH v4 10/11] xen: modify page table construction |
Date: |
Mon, 22 Feb 2016 13:18:58 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Feb 22, 2016 at 10:29:04AM +0100, Juergen Gross wrote:
> On 22/02/16 10:17, Daniel Kiper wrote:
> > On Mon, Feb 22, 2016 at 07:03:18AM +0100, Juergen Gross wrote:
> >> Modify the page table construction to allow multiple virtual regions
> >> to be mapped. This is done as preparation for removing the p2m list
> >> from the initial kernel mapping in order to support huge pv domains.
> >>
> >> This allows a cleaner approach for mapping the relocator page by
> >> using this capability.
> >>
> >> The interface to the assembler level of the relocator has to be changed
> >> in order to be able to process multiple page table areas.
> >>
> >> Signed-off-by: Juergen Gross <address@hidden>
> >> ---
> >> V4: align variables in assembly sources
> >> use separate structure define as requested by Daniel Kiper
> >>
> >> V3: use constants instead of numbers as requested by Daniel Kiper
> >> add lots of comments to assembly code as requested by Daniel Kiper
> >> ---
> >> grub-core/lib/i386/xen/relocator.S | 88 ++++++----
> >> grub-core/lib/x86_64/xen/relocator.S | 135 ++++++---------
> >> grub-core/lib/xen/relocator.c | 28 ++-
> >> grub-core/loader/i386/xen.c | 325
> >> ++++++++++++++++++++++++-----------
> >> include/grub/i386/memory.h | 7 +
> >> include/grub/xen/relocator.h | 6 +-
> >> 6 files changed, 359 insertions(+), 230 deletions(-)
> >>
> >> diff --git a/grub-core/lib/i386/xen/relocator.S
> >> b/grub-core/lib/i386/xen/relocator.S
> >> index 694a54c..f8d135a 100644
> >> --- a/grub-core/lib/i386/xen/relocator.S
> >> +++ b/grub-core/lib/i386/xen/relocator.S
> >> @@ -102,6 +112,10 @@ VARIABLE(grub_relocator_xen_remap_continue)
> >>
> >> jmp *%eax
> >>
> >> + .p2align 2
> >
> > I do not think this is needed but...
>
> Even if the processor does allow unaligned loads: it's cleaner to
> avoid them.
I do not think that it pays here. However, if you are going
to leave .p2align please align other variables too.
> >> diff --git a/grub-core/lib/x86_64/xen/relocator.S
> >> b/grub-core/lib/x86_64/xen/relocator.S
> >> index 92e9e72..38ae157 100644
> >> --- a/grub-core/lib/x86_64/xen/relocator.S
> >> +++ b/grub-core/lib/x86_64/xen/relocator.S
> >>
> >> jmp *%rax
> >>
> >> -LOCAL(mmu_op):
> >> + .p2align 3
> >
> > Ditto...
> >
> >> diff --git a/grub-core/lib/xen/relocator.c b/grub-core/lib/xen/relocator.c
> >> index 8f427d3..a05b253 100644
> >> --- a/grub-core/lib/xen/relocator.c
> >> +++ b/grub-core/lib/xen/relocator.c
> >> @@ -29,6 +29,11 @@
> >>
> >> typedef grub_addr_t grub_xen_reg_t;
> >>
> >> +struct grub_relocator_xen_paging_area {
> >> + grub_xen_reg_t start;
> >> + grub_xen_reg_t size;
> >> +};
> >> +
> >
> > ... this should have GRUB_PACKED because compiler may
> > add padding to align size member.
>
> Why would the compiler add padding to a structure containing two items
> of the same type? I don't think the C standard would allow this.
>
> grub_xen_reg_t is either unsigned (32 bit) or unsigned long (64 bit).
> There is no way this could require any padding.
You are right but we should add this here just in case.
Daniel
- [PATCH v4 01/11] xen: make xen loader callable multiple times, (continued)
- [PATCH v4 01/11] xen: make xen loader callable multiple times, Juergen Gross, 2016/02/22
- [PATCH v4 05/11] xen: synchronize xen header, Juergen Gross, 2016/02/22
- [PATCH v4 11/11] xen: add capability to load p2m list outside of kernel mapping, Juergen Gross, 2016/02/22
- [PATCH v4 06/11] xen: factor out p2m list allocation into separate function, Juergen Gross, 2016/02/22
- [PATCH v4 04/11] xen: add elfnote.h to avoid using numbers instead of constants, Juergen Gross, 2016/02/22
- [PATCH v4 03/11] xen: reduce number of global variables in xen loader, Juergen Gross, 2016/02/22
- [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction, Daniel Kiper, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction,
Daniel Kiper <=
- Re: [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction, Daniel Kiper, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/22
- Re: [PATCH v4 10/11] xen: modify page table construction, Andrei Borzenkov, 2016/02/25
- Re: [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/29
- Re: [PATCH v4 10/11] xen: modify page table construction, Juergen Gross, 2016/02/29
- Re: [PATCH v4 10/11] xen: modify page table construction, Andrei Borzenkov, 2016/02/29