[PATCH 3/5] x86/pvh: Set phys_base when calling xen_prepare_pvh()

Jason Andryuk
2024-04-10T19:49:06Z

phys_base needs to be set for __pa() to work in xen_pvh_init() when
finding the hypercall page. Set it before calling into
xen_prepare_pvh(), which calls xen_pvh_init(). Clear it afterward to
avoid __startup_64() adding to it and creating an incorrect value.

Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
---
Instead of setting and clearing phys_base, a dedicated variable could be
used just for the hypercall page. Having phys_base set properly may
avoid further issues if the use of phys_base or __pa() grows.
---
arch/x86/platform/pvh/head.S | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index bb1e582e32b1..c08d08d8cc92 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -125,7 +125,17 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
xor %edx, %edx
wrmsr

+ /* Calculate load offset from LOAD_PHYSICAL_ADDR and store in
+ * phys_base. __pa() needs phys_base set to calculate the
+ * hypercall page in xen_pvh_init(). */
+ movq %rbp, %rbx
+ subq $LOAD_PHYSICAL_ADDR, %rbx
+ movq %rbx, phys_base(%rip)
call xen_prepare_pvh
+ /* Clear phys_base. __startup_64 will *add* to its value,
+ * so reset to 0. */
+ xor %rbx, %rbx
+ movq %rbx, phys_base(%rip)

/* startup_64 expects boot_params in %rsi. */
lea rva(pvh_bootparams)(%ebp), %rsi
--
2.44.0