x86/hyperv: fix invalid writes to MSRs during root partition kexec

hyperv_cleanup resets the hypercall page by setting the MSR to 0. However,
the root partition is not allowed to write to the GPA bits of the MSR.
Instead, it uses the hypercall page provided by the MSR. Similar is the
case with the reference TSC MSR.

Clear only the enable bit instead of zeroing the entire MSR to make
the code valid for root partition too.

Signed-off-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20221027095729.1676394-3-anrayabh@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index d46f70522ddf2b74b36fc092895aa784b0d44c5f..f49bc3ec76e6a5af25650033795d574a9844244a 100644 (file)
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -535,6 +535,7 @@ common_free:
 void hyperv_cleanup(void)
 {
        union hv_x64_msr_hypercall_contents hypercall_msr;
+       union hv_reference_tsc_msr tsc_msr;
 
        unregister_syscore_ops(&hv_syscore_ops);
 
@@ -550,12 +551,14 @@ void hyperv_cleanup(void)
        hv_hypercall_pg = NULL;
 
        /* Reset the hypercall page */
-       hypercall_msr.as_uint64 = 0;
-       wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+       hypercall_msr.as_uint64 = hv_get_register(HV_X64_MSR_HYPERCALL);
+       hypercall_msr.enable = 0;
+       hv_set_register(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
 
        /* Reset the TSC page */
-       hypercall_msr.as_uint64 = 0;
-       wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
+       tsc_msr.as_uint64 = hv_get_register(HV_X64_MSR_REFERENCE_TSC);
+       tsc_msr.enable = 0;
+       hv_set_register(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 }
 
 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)