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From: Sean Christopherson <seanjc@google.com>
To: Tyler Stachecki <stachecki.tyler@gmail.com>
Cc: Leonardo Bras <leobras@redhat.com>,
	Dongli Zhang <dongli.zhang@oracle.com>,
	kvm@vger.kernel.org, pbonzini@redhat.com, dgilbert@redhat.com,
	tglx@linutronix.de, mingo@redhat.com,
	dave.hansen@linux.intel.com, bp@alien8.de,
	Tyler Stachecki <tstachecki@bloomberg.net>,
	stable@vger.kernel.org
Subject: Re: [PATCH] x86/kvm: Account for fpstate->user_xfeatures changes
Date: Tue, 26 Sep 2023 10:31:51 -0700	[thread overview]
Message-ID: <ZRMVh0CMmfMo3kmc@google.com> (raw)
In-Reply-To: <ZRMHY83W/VPjYyhy@google.com>

On Tue, Sep 26, 2023, Sean Christopherson wrote:
> Masking fpstate->user_xfeatures is buggy for another reason: it's destructive if
> userspace calls KVM_SET_CPUID multiple times.  No real world userspace actually
> calls KVM_SET_CPUID to "expand" features, but it's technically possible and KVM
> is supposed to allow it.

This particular bit is wrong, KVM overwrites user_xfeatures, it doesn't AND it.
I misremembered the code.

  reply	other threads:[~2023-09-26 17:31 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-14  1:00 [PATCH] x86/kvm: Account for fpstate->user_xfeatures changes Tyler Stachecki
2023-09-14  1:33 ` Tyler Stachecki
2023-09-14  7:15 ` Leonardo Bras
2023-09-14  9:11   ` Tyler Stachecki
2023-09-14 17:05     ` Dongli Zhang
2023-09-15  0:58       ` Tyler Stachecki
2023-09-15  7:41         ` Leonardo Bras
2023-09-15 12:27           ` Tyler Stachecki
2023-09-25 21:26             ` Sean Christopherson
2023-09-26  3:02               ` Tyler Stachecki
2023-09-26 16:31                 ` Sean Christopherson
2023-09-26 17:31                   ` Sean Christopherson [this message]
2023-09-26 19:22                   ` Sean Christopherson
2023-09-26 20:27                     ` Sean Christopherson
2023-09-15  7:13       ` Leonardo Bras
2023-09-15  7:11     ` Leonardo Bras

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