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Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system
From: |
Xu, Anthony |
Subject: |
Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode |
Date: |
Tue, 16 May 2017 20:00:28 +0000 |
> On Sat, May 13, 2017 at 01:24:30AM +0000, Xu, Anthony wrote:
> > I think it is related to accel and platform, the result I gave before is
> > for q35
> tcg,
> >
> > With the above change, I got below data
> >
> > Platform accel count of restoring A20 to 0
> > Q35 kvm 96
> > Q35 tcg 271
> > PC kvm 3
> > PC tcg 3
>
> Okay, thanks. I think the number of a20 switches is due to
> differences in option rom execution interacting with the fact that
> some mode switches were occurring before SeaBIOS set
> call16_override().
>
> > But I still see a lot of PORT_A20 accesses in QEMU as I expected
>
> Yes, but it should be possible to significantly reduce the number of
> outb() calls by limiting them to when A20 changes. This should also
> be useful to reduce the number of outb() calls needed to disable NMIs.
> I sent a patch series to the seabios mailing list to demonstrate the
> idea.
If both TCG and KVM work by ignoring A20, why not remove all PORT_A20
access in SeaBios when CONFIG_DISABLE_A20 is not defined?
Do you see any impact?
-Anthony
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, (continued)
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Kevin O'Connor, 2017/05/11
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Xu, Anthony, 2017/05/11
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Paolo Bonzini, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Xu, Anthony, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Paolo Bonzini, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Kevin O'Connor, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Xu, Anthony, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Kevin O'Connor, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Xu, Anthony, 2017/05/12
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Kevin O'Connor, 2017/05/16
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode,
Xu, Anthony <=
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Kevin O'Connor, 2017/05/16
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Xu, Anthony, 2017/05/16
- Re: [Qemu-devel] [PATCH] target/i386: enable A20 automatically in system management mode, Paolo Bonzini, 2017/05/17