linux-kernel - Re: [PATCH -v5.1] x86/kvm: Implement HWCR support

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Date:   Thu, 18 Apr 2019 16:19:49 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     KVM <kvm@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tony Luck <tony.luck@...el.com>,
        Yazen Ghannam <Yazen.Ghannam@....com>
Subject: Re: [PATCH -v5.1] x86/kvm: Implement HWCR support

On Thu, Apr 18, 2019 at 06:56:06AM -0700, Sean Christopherson wrote:
> This doesn't allow writing '0' regardless of msr_hwcr.BIT(18), which was
> previously supported.

Restored the old conditional:

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 10f6acc6494c..f74f1280745b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2318,7 +2318,8 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 				return -1;
 
 			/* MCi_STATUS */
-			if ((offset & 0x3) == 1 && !msr_info->host_initiated) {
+			if (!msr_info->host_initiated &&
+			    (offset & 0x3) == 1 && data != 0) {
 				if (!can_set_mci_status(vcpu))
 					return -1;
 			}

> And there's no need for multiple if statements.

It is a bit more readable this way.

Actually, I'd break that if above into smaller if-statements with
flipped logic to make it even more readable:

	if (msr_info->host_initiated)
		goto set_msr;

	if (!(offset & 0x3))
		goto set_msr;

	if (!data)
		goto set_msr;

	if (!can_set_mci_status(vcpu))
		return -1;

set_msr:
	...


Anything else? Can I send v5.2 now?

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.