From: Dave Hansen <dave.hansen@intel.com>
To: Marc Orr <marcorr@google.com>,
kvm@vger.kernel.org, jmattson@google.com, rientjes@google.com,
konrad.wilk@oracle.com, linux-mm@kvack.org,
akpm@linux-foundation.org, pbonzini@redhat.com,
rkrcmar@redhat.com, willy@infradead.org,
sean.j.christopherson@intel.com, dave.hansen@linux.intel.com,
kernellwp@gmail.com
Subject: Re: [kvm PATCH v6 2/2] kvm: x86: Dynamically allocate guest_fpu
Date: Thu, 1 Nov 2018 10:09:26 -0700 [thread overview]
Message-ID: <86c27c0c-1326-c757-9b43-251f2290182b@intel.com> (raw)
In-Reply-To: <20181031234928.144206-3-marcorr@google.com>
On 10/31/18 4:49 PM, Marc Orr wrote:
> + if (!boot_cpu_has(X86_FEATURE_FPU) || !boot_cpu_has(X86_FEATURE_FXSR)) {
> + printk(KERN_ERR "kvm: inadequate fpu\n");
> + r = -EOPNOTSUPP;
> + goto out;
> + }
It would be nice to have a comment about _why_ this is inadequate.
> r = -ENOMEM;
> + x86_fpu_cache = kmem_cache_create_usercopy(
> + "x86_fpu",
For now, this should probably be kvm_x86_fpu since it's not used as a
generic x86 thing, yet.
Also, why is this a "usercopy"? "fpu_kernel_xstate_size" includes (or
will soon include) supervisor state which can never be copied to
userspace. If this structure is going out to userspace, that tells me
we might instead want fpu_user_xstate_size, *or* we want the
non-usercopy variant.
next prev parent reply other threads:[~2018-11-01 17:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-31 23:49 [kvm PATCH v6 0/2] shrink vcpu_vmx down to order 2 Marc Orr
2018-10-31 23:49 ` [kvm PATCH v6 1/2] kvm: x86: Use task structs fpu field for user Marc Orr
2018-10-31 23:49 ` [kvm PATCH v6 2/2] kvm: x86: Dynamically allocate guest_fpu Marc Orr
2018-11-01 17:09 ` Dave Hansen [this message]
2018-11-01 17:35 ` Marc Orr
2018-11-05 10:08 ` Paolo Bonzini
2018-11-05 5:04 ` [LKP] [kvm] ac347c1bc8: WARNING:at_mm/slab_common.c:#kmem_cache_create_usercopy kernel test robot
2021-05-21 20:58 ` [kvm PATCH v6 0/2] shrink vcpu_vmx down to order 2 Jim Mattson
2021-05-24 12:50 ` Paolo Bonzini
2021-05-24 22:44 ` Sean Christopherson
2021-05-24 23:01 ` Jim Mattson
2021-05-25 0:00 ` Sean Christopherson
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