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    SubjectRe: efi_enabled(EFI_PARAVIRT) use
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    On 2016年04月29日 22:53, Ard Biesheuvel wrote:
    > On 29 April 2016 at 16:39, Matt Fleming <matt@codeblueprint.co.uk> wrote:
    >> On Fri, 29 Apr, at 11:34:45AM, Stefano Stabellini wrote:
    >>> On Fri, 29 Apr 2016, Ingo Molnar wrote:
    >>>> Also, it would be nice to have all things EFI in a single tree, the conflicts are
    >>>> going to be painful! There's very little reason not to carry this kind of commit:
    >>>>
    >>>> arch/arm/xen/enlighten.c | 6 +++++
    >>>> drivers/firmware/efi/arm-runtime.c | 17 +++++++++-----
    >>>> drivers/firmware/efi/efi.c | 45 ++++++++++++++++++++++++++++++++------
    >>>> 3 files changed, 56 insertions(+), 12 deletions(-)
    >>>>
    >>>> in the EFI tree.
    >>>
    >>> That's true. I'll drop this commit from xentip and let Matt pick it up
    >>> or request changes as he sees fit.
    >>
    >> One small change I think would be sensible to make is to expand
    >> EFI_PARAVIRT into a few more bits to clearly indicate the quirks on
    >> Xen, and in the process, to delete EFI_PARAVIRT.
    >>
    Sure. How should I add this change? Rework this patch or add new one on
    top of it?

    >> That should address Ingo's major concern, and also make it much easier
    >> to rework the code in a piecemeal fashion.
    >>
    >> Could somebody enumerate the things that make Xen (dom0) different on
    >> arm* compared with bare metal EFI boot? The list I made for x86 was,
    >>
    >> 1. Has no EFI memory map
    >> 2. Runtime regions do not need to be mapped
    >> 3. Cannot call SetVirtualAddressMap()
    >> 4. /sys/firmware/efi/fw_vendor is invisible
    >>
    >> The first maps to not setting EFI_MEMMAP, the second to not setting
    >> EFI_RUNTIME. If we add EFI_ALREADY_VIRTUAL and EFI_FW_VENDOR_INVISIBLE
    >> to efi.flags that should cover everything on x86. Does arm* require
    >> anything else?
    >
    > I already proposed when this patch was first under review to make the
    > arm_enable_runtime_services() function bail early without error if the
    > EFI_RUNTIME_SERVICES flag is already set, and the xen code could set
    > that bit as well when it installs its paravirtualized alternatives. I
    > don't remember exactly why that was shot down, though, but I think it
    > is the only reason this code introduces references to EFI_PARAVIRT in
    > the first place.
    >
    Yes, in this patch we could set EFI_RUNTIME_SERVICES flag in
    fdt_find_hyper_node instead of setting EFI_PARAVIRT flag, and then bail
    out early in arm_enable_runtime_services() as you said. Then call
    xen_efi_runtime_setup() in xen_guest_init().

    While I still have a question, in this patch we use
    efi_enabled(EFI_PARAVIRT) as a condition to make fdt_find_uefi_params()
    and efi_get_fdt_params() execute different ways. So it needs to find a
    new condition for that if we need to get rid of EFI_PARAVIRT. One I
    think is that xen_initial_domain() check. Is that fine?

    Thanks,
    --
    Shannon

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