From: Roman Kisel <rom...@linux.microsoft.com>

[ Upstream commit f285d995743269aa9f893e5e9a1065604137c1f6 ]

The Top-Level Functional Specification for Hyper-V, Section 3.6 [1, 2],
disallows overlapping of the input and output hypercall areas, and
hv_vtl_apicid_to_vp_id() overlaps them.

Use the output hypercall page of the current vCPU for the hypercall.

[1] 
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface
[2] https://github.com/MicrosoftDocs/Virtualization-Documentation/tree/main/tlfs

Reported-by: Michael Kelley <mhkli...@outlook.com>
Closes: 
https://lore.kernel.org/lkml/sn6pr02mb4157b98cd34781cc87a9d921d4...@sn6pr02mb4157.namprd02.prod.outlook.com/
Signed-off-by: Roman Kisel <rom...@linux.microsoft.com>
Reviewed-by: Easwar Hariharan <eahar...@linux.microsoft.com>
Reviewed-by: Nuno Das Neves <nunodasne...@linux.microsoft.com>
Link: 
https://lore.kernel.org/r/20250108222138.1623703-6-rom...@linux.microsoft.com
Signed-off-by: Wei Liu <wei....@kernel.org>
Message-ID: <20250108222138.1623703-6-rom...@linux.microsoft.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 arch/x86/hyperv/hv_vtl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 04775346369c5..4e1b1e3b56584 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -189,7 +189,7 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id)
        input->partition_id = HV_PARTITION_ID_SELF;
        input->apic_ids[0] = apic_id;
 
-       output = (u32 *)input;
+       output = *this_cpu_ptr(hyperv_pcpu_output_arg);
 
        control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
        status = hv_do_hypercall(control, input, output);
-- 
2.39.5


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