From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Wanpeng Li <wanpeng.li@linux.intel.com>
Subject: Re: [PATCH] KVM: cpuid: mask more bits in leaf 0xd and subleaves
Date: Wed, 3 Dec 2014 13:07:40 +0100 [thread overview]
Message-ID: <20141203120739.GA26617@potion.brq.redhat.com> (raw)
In-Reply-To: <547EC40E.5010506@redhat.com>
2014-12-03 09:04+0100, Paolo Bonzini:
> On 03/12/2014 00:05, Radim Krčmář wrote:
> > 2014-12-02 14:09+0100, Paolo Bonzini:
> >> + } else {
> >> + if (entry[i].eax == 0 || !(supported & mask))
> >> + continue;
> >> + WARN_ON_ONCE(entry[i].ecx & 1);
> >> + entry[i].ecx &= 1;
> >
> > ECX Bit 0 is set if the sub-leaf index, n, maps to a valid bit in the
> > IA32_XSS MSR and bit 0 is clear if n maps to a valid bit in XCR0.
> >
> > ECX should be set to 0 instead, we definitely don't map to a valid bit
> > in IA32_XSS now.
>
> Well, there is a WARN just above. :) But I can change it to zero instead.
Yeah, I wasn't sure about the WARN ... I can only see it trigger after
host xcr0 changes and we are much more screwed in that case anyway :)
(But it has a chance of catching a bug, so it isn't only bad.)
The guest expects 0 here, so I'd rather have it ...
> > (Having only one part of cpuid ready for it is weird ...)
> >
> >> + }
> >> + entry[i].edx = 0;
> >> entry[i].flags |=
> >> KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> >
> > (Unrelated, I have yet to understand how this flag translates
> > * If ECX contains an invalid sub-leaf index, EAX/EBX/ECX/EDX return 0.)
>
> If the index is invalid, entry[i].eax is zero and we do not return
> anything at all.
I see, the field is sparse and "++*nent; ++i;", not the flag, does it,
thanks.
next prev parent reply other threads:[~2014-12-03 12:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-02 13:09 [PATCH] KVM: cpuid: mask more bits in leaf 0xd and subleaves Paolo Bonzini
2014-12-02 23:05 ` Radim Krčmář
2014-12-03 8:04 ` Paolo Bonzini
2014-12-03 12:07 ` Radim Krčmář [this message]
2014-12-03 12:10 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20141203120739.GA26617@potion.brq.redhat.com \
--to=rkrcmar@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=wanpeng.li@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.