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Dadhania wrote: >> On 12/9/2024 9:27 PM, Borislav Petkov wrote: >>> On Tue, Dec 03, 2024 at 02:30:36PM +0530, Nikunj A Dadhania wrote: >>> + >>> + if (write) { >>> + WARN_ONCE(1, "TSC MSR writes are verboten!\n"); >>> + return ES_UNSUPPORTED; >> >> Sure, we can add a WARN_ONCE(). > > You'll want to test this... IIRC, I'm not sure if a WARN_ONCE() will be > properly printed when issued within the #VC handler (since it will > generate a nested #VC). Right, a write to TSC MSR generates the following splat: [ 17.450076] ------------[ cut here ]------------ [ 17.450077] TSC MSR writes are verboten! [ 17.450079] WARNING: CPU: 0 PID: 617 at arch/x86/coco/sev/core.c:1456 vc_handle_exitcode.part.0+0xe54/0x1110 [ 17.450090] CPU: 0 UID: 0 PID: 617 Comm: wrmsr Tainted: G S 6.13.0-rc1-00093-g5e3143d631a9-dirty #121 Regards, Nikunj