Re: [PATCH for-4.19 v2] x86/pvh: declare PVH dom0 supported with caveats

[George Dunlap <george.dunlap@xxxxxxxxx>]

On Mon, Jun 10, 2024 at 9:50 AM Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> PVH dom0 is functionally very similar to PVH domU except for the domain
> builder and the added set of hypercalls available to it.
>
> The main concern with declaring it "Supported" is the lack of some features
> when compared to classic PV dom0, hence switch it's status to supported with
> caveats.  List the known missing features, there might be more features 
> missing
> or not working as expected apart from the ones listed.
>
> Note there's some (limited) PVH dom0 testing on both osstest and gitlab.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> ---
> Changes since v1:
>  - Remove boot warning.
> ---
>  CHANGELOG.md                  |  1 +
>  SUPPORT.md                    | 15 ++++++++++++++-
>  xen/arch/x86/hvm/dom0_build.c |  1 -
>  3 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/CHANGELOG.md b/CHANGELOG.md
> index 201478aa1c0e..1778419cae64 100644
> --- a/CHANGELOG.md
> +++ b/CHANGELOG.md
> @@ -14,6 +14,7 @@ The format is based on [Keep a 
> Changelog](https://keepachangelog.com/en/1.0.0/)
>     - HVM PIRQs are disabled by default.
>     - Reduce IOMMU setup time for hardware domain.
>     - Allow HVM/PVH domains to map foreign pages.
> +   - Declare PVH dom0 supported with caveats.
>   - xl/libxl configures vkb=[] for HVM domains with priority over vkb_device.
>   - Increase the maximum number of CPUs Xen can be built for from 4095 to
>     16383.
> diff --git a/SUPPORT.md b/SUPPORT.md
> index d5d60c62ec11..711aacf34662 100644
> --- a/SUPPORT.md
> +++ b/SUPPORT.md
> @@ -161,7 +161,20 @@ Requires hardware virtualisation support (Intel VMX / 
> AMD SVM).
>  Dom0 support requires an IOMMU (Intel VT-d / AMD IOMMU).
>
>      Status, domU: Supported
> -    Status, dom0: Experimental
> +    Status, dom0: Supported, with caveats
> +
> +PVH dom0 hasn't received the same test coverage as PV dom0, so it can exhibit
> +unexpected behavior or issues on some hardware.

What's the criteria for removing this paragraph?

FAOD I'm OK with it being checked in as-is, but I feel like this
paragraph is somewhat anomalous, and would at least like to have an
idea what might trigger its removal.

 -George