Hi Stefano,
On 5/3/2024 2:08 AM, Stefano Stabellini wrote:
On Fri, 26 Apr 2024, Henry Wang wrote:
For use cases such as Dom0less PV drivers, a mechanism to communicate
Dom0less DomU's static data with the runtime control plane (Dom0) is
needed. Since on Arm HVMOP is already the existing approach to address
such use cases (for example the allocation of HVM_PARAM_CALLBACK_IRQ),
add a new HVMOP key HVM_PARAM_MAGIC_BASE_PFN for storing the magic
page region base PFN. The value will be set at Dom0less DomU
construction time after Dom0less DomU's magic page region has been
allocated.
To keep consistent, also set the value for HVM_PARAM_MAGIC_BASE_PFN
for libxl guests in alloc_magic_pages().
Reported-by: Alec Kwapis <alec.kwa...@medtronic.com>
Signed-off-by: Henry Wang <xin.wa...@amd.com>
---
tools/libs/guest/xg_dom_arm.c | 2 ++
xen/arch/arm/dom0less-build.c | 2 ++
xen/arch/arm/hvm.c | 1 +
xen/include/public/hvm/params.h | 1 +
4 files changed, 6 insertions(+)
diff --git a/tools/libs/guest/xg_dom_arm.c b/tools/libs/guest/xg_dom_arm.c
index 8cc7f27dbb..3c08782d1d 100644
--- a/tools/libs/guest/xg_dom_arm.c
+++ b/tools/libs/guest/xg_dom_arm.c
@@ -74,6 +74,8 @@ static int alloc_magic_pages(struct xc_dom_image *dom)
xc_clear_domain_page(dom->xch, dom->guest_domid, base +
MEMACCESS_PFN_OFFSET);
xc_clear_domain_page(dom->xch, dom->guest_domid, dom->vuart_gfn);
+ xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_MAGIC_BASE_PFN,
+ base);
xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_CONSOLE_PFN,
dom->console_pfn);
xc_hvm_param_set(dom->xch, dom->guest_domid, HVM_PARAM_STORE_PFN,
diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index 40dc85c759..72187c167d 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -861,6 +861,8 @@ static int __init construct_domU(struct domain *d,
free_domheap_pages(magic_pg,
get_order_from_pages(NR_MAGIC_PAGES));
return rc;
}
+
+ d->arch.hvm.params[HVM_PARAM_MAGIC_BASE_PFN] = gfn_x(gfn);
I apologize as I have not read the whole email thread in reply to this
patch.
Why do we need to introduce a new hvm param instead of just setting
HVM_PARAM_CONSOLE_PFN and HVM_PARAM_STORE_PFN directly here?
Yeah this is a good question, I aIso thought about this but in the end
didn't do that directly because I don't really want to break the current
protocol between Linux, Xen and toolstack.
In docs/features/dom0less.pandoc, section "PV Drivers", there is a
communication protocol saying that Xen should keep the
HVM_PARAM_STORE_PFN to ~0ULL until the toolstack sets the
HVM_PARAM_STORE_PFN.
I am open to change the protocol (changes might be needed in the Linux
side too), if it is ok to do that, I can set the HVM params here
directly and change the doc accordingly.
Kind regards,
Henry
