linux-kernel - Re: [PATCH] x86/hyper-v: Filter non-canonical addresses passed via HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST(

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Message-ID: <15fa8a27-958f-42d2-ac1f-0fce248cfc1f@tum.de>
Date: Thu, 26 Jun 2025 15:49:02 +0200
From: Manuel Andreas <manuel.andreas@....de>
To: Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>, pbonzini@...hat.com
Subject: Re: [PATCH] x86/hyper-v: Filter non-canonical addresses passed via
 HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST(_EX)

On 6/26/25 12:25 AM, Sean Christopherson wrote:
> On Wed, 25 Jun 2025 15:53:19 +0200, Manuel Andreas wrote:
>> In KVM guests with Hyper-V hypercalls enabled, the hypercalls
>> HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST and HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX
>> allow a guest to request invalidation of portions of a virtual TLB.
>> For this, the hypercall parameter includes a list of GVAs that are supposed
>> to be invalidated.
>>
>> However, when non-canonical GVAs are passed, there is currently no
>> filtering in place and they are eventually passed to checked invocations of
>> INVVPID on Intel / INVLPGA on AMD.
>> While the AMD variant (INVLPGA) will silently ignore the non-canonical
>> address and perform a no-op, the Intel variant (INVVPID) will fail and end
>> up in invvpid_error, where a WARN_ONCE is triggered:
>>
>> [...]
> 
> Applied to kvm-x86 fixes, with a massaged changelog, e.g. to call out that
> "real" Hyper-V behaves this way.  Thanks!
> 
> [1/1] x86/hyper-v: Filter non-canonical addresses passed via HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST(_EX)
>        https://github.com/kvm-x86/linux/commit/fa787ac07b3c

Thanks for the quick approval and Vitaly for the Hyper-V testing!