From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A70613A0B36 for ; Sat, 12 Sep 2026 07:30:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789198205; cv=none; b=dOnw1S9D+NfAqo6ibo/pEiRrKpq2+p+h+GK8tNKL14bXc+QsjCzyLIHDazh6UvikXZLWGnTFDI5+YboBwu+fD6XLK7K4ZDnW8JBTb26Ccz2QsKRAUBEpLeP9iRKJFCd/fWY2T+X34SXKU290FgxxQgmwYlAzQrFaVOuPebLIArg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789198205; c=relaxed/simple; bh=9xmDwIJXv8L7N9NrAJj92+QxRvL7KpgrKc/hpWtuVtA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sO4sYMZ/fD20X23FF9Pjc/HJ2B5cNQEZRmAD7XsHadou+4PRA6j3w5QD7sjyIf8WLN+HNDQuDkJx8rmnNSOfJ2Z4N32LFtqQwbzN86JzRE4dv3jmJOnnOmgHc7OTkYxQJnUcw0iRcrRl/cJ5i4mQPTIPynHQnt1bL9aN2H2sxp0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=hdhMZ+sC; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="hdhMZ+sC" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 49A1E16F2; Sat, 12 Sep 2026 00:29:59 -0700 (PDT) Received: from [10.57.10.2] (unknown [10.57.10.2]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6C2F93F7D8; Sat, 12 Sep 2026 00:30:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789198202; bh=9xmDwIJXv8L7N9NrAJj92+QxRvL7KpgrKc/hpWtuVtA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hdhMZ+sCKY9b1Z9bZRkHsLOQ54Fsj1pwUYmGkBYtSJr+3wwGONmgg/5QurTTd3LkE c1ZzysJnJUGxDId0PUkxMM4MuCtksyqyyhhtMf8zAnrQ30X4Sjn7si6tPg6mq27PP7 xNm3PHW29zFh6BhQCY30u0Xx+FAbGKkbaLTJnb58= Message-ID: Date: Sat, 12 Sep 2026 08:29:59 +0100 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH kvmtool 5/5] arm64: Query counter-offset support on the VM fd Content-Language: en-GB To: Fuad Tabba , kvm@vger.kernel.org Cc: kvmarm@lists.linux.dev, Will Deacon , Julien Thierry , Alexandru Elisei , Andre Przywara , Oliver Upton , Marc Zyngier , Fuad Tabba References: <20260831192406.1341841-1-fuad.tabba@linux.dev> <20260831192406.1341841-6-fuad.tabba@linux.dev> From: Suzuki K Poulose In-Reply-To: <20260831192406.1341841-6-fuad.tabba@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 31/08/2026 20:24, Fuad Tabba wrote: > kvm__arch_set_counter_offset() probes KVM_CAP_COUNTER_OFFSET with > kvm__supports_extension(), which issues KVM_CHECK_EXTENSION on the > global /dev/kvm fd. That reports the host's raw capabilities, unaware of > any per-VM restrictions. > > pKVM does not offer the counter offset to a protected VM, and reflects > that on the VM fd alone. kvmtool's own check passes, and the > KVM_ARM_SET_COUNTER_OFFSET that follows is refused by > commit b12b3b04f6ba ("KVM: arm64: Check whether a VM IOCTL is allowed > in pKVM"): > > KVM_ARM_SET_COUNTER_OFFSET: Invalid argument > > Query it on the VM fd via kvm__supports_vm_extension(), so > --counter-offset on a protected VM fails with kvmtool's own message: > > Fatal: No support for global counter offset > > Signed-off-by: Fuad Tabba Reviewed-by: Suzuki K Poulose > --- > arm64/kvm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arm64/kvm.c b/arm64/kvm.c > index 36b3284..0bb3535 100644 > --- a/arm64/kvm.c > +++ b/arm64/kvm.c > @@ -155,7 +155,7 @@ static void kvm__arch_set_counter_offset(struct kvm *kvm) > if (!kvm->cfg.arch.counter_offset) > return; > > - if (!kvm__supports_extension(kvm, KVM_CAP_COUNTER_OFFSET)) > + if (!kvm__supports_vm_extension(kvm, KVM_CAP_COUNTER_OFFSET)) > die("No support for global counter offset"); > > if (ioctl(kvm->vm_fd, KVM_ARM_SET_COUNTER_OFFSET, &offset))