linux-kernel - [PATCH v5 5/5] hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp

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Message-Id: <20241230180941.244418-6-romank@linux.microsoft.com>
Date: Mon, 30 Dec 2024 10:09:41 -0800
From: Roman Kisel <romank@...ux.microsoft.com>
To: hpa@...or.com,
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Subject: [PATCH v5 5/5] hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()

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 <mhklinux@...look.com>
Closes: https://lore.kernel.org/lkml/SN6PR02MB4157B98CD34781CC87A9D921D40D2@SN6PR02MB4157.namprd02.prod.outlook.com/
Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
---
 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 04775346369c..4e1b1e3b5658 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);
-- 
2.34.1